This document summarizes the key components of plant cell walls and how they are synthesized and assembled. Plant cell walls are composed of cellulose microfibrils cross-linked by hemicelluloses and pectins. These components include cellulose, callose, pectins, xyloglucans, and xylans. They are synthesized in the Golgi and plasma membrane by glycosyltransferases and cellulose synthases and transported to the cell wall. Proper assembly of the cell wall components is essential for determining plant growth, shape and mechanical strength.
Cell wall in plants- introduction, cell wall layers, functions, sugars the building blocks of cell wall, macromolecules of cell wall, cell wall architecture, biosynthesis and assembly
The document summarizes recent findings regarding two Arabidopsis mutants involved in plant cell expansion.
The first mutant is rsw1, which encodes a subunit of cellulose synthase. At restrictive temperatures, rsw1 cells produce non-crystalline glucan instead of cellulose microfibrils. This supports the role of RSW1 in cellulose synthesis.
The second mutant is korrigan, which encodes an unusual endo-1,4-β-glucanase enzyme. kor cells have thick, undulating cell walls that lack the layered microfibril structure of wild-type walls. This suggests KORRIGAN is involved in remodeling of the cell wall during
The document summarizes the composition and architecture of plant cell walls. It discusses the primary components of plant cell walls including cellulose, hemicellulose, pectin and lignin. It describes how these components interact through different proposed models and compares the structure of primary and secondary cell walls. Secondary cell walls are thicker and stronger and contain more lignin, which provides rigidity important for conducting tissues. The recalcitrance of secondary cell walls is important for applications in biofuels and pulp/paper industries.
This document describes a protocol for engineering cardiac tissue using perfusion bioreactor systems. Cardiac cells are seeded onto porous scaffolds and cultured in bioreactors with perfusion of culture medium, which provides oxygen to the cells and overcomes limitations of conventional static culture. Two approaches are discussed: interstitial flow through porous scaffolds and flow through channel arrays in scaffolds. Perfusion improves cell viability, density, and function compared to static culture and enables engineering of thicker cardiac constructs.
The distribution of callose synthase, cellulose synthase, and sucrose synthase in tobacco pollen tubes is controlled by actin filaments and microtubules in different ways. Cellulose synthase is present along the entire length of pollen tubes, with higher concentration at the apex, while callose synthase is located in the apex and around callose plugs. Actin filaments and endomembrane dynamics control the distribution of both enzymes by transporting them via Golgi bodies and vesicles. Microtubules control the positioning of callose synthase in distal regions and around plugs, but only partially influence cellulose synthase distribution. Sucrose synthase binds to actin filaments and provides UDP-
Biomaterial is any matter or construct that interacts with biological systems. Biomaterials are often produced in nature or synthesized in the lab using metallic, ceramic, or chemical approaches. They are used for medical applications like implants and prosthetics. Biomaterials must be biocompatible with the human body. The field of biomaterials science incorporates elements of medicine, biology, chemistry, and materials science to develop these materials.
A recent publication by Dr. Sachin Kadam, CTO of Advancells, sheds light on natural osteoinductive bio-compatible scaffolds for effective clinical applications on musculoskeletal disorders. These scaffolds can enhance the efficiency of stem cell transplantation, and thus improve healthcare manifold.
Los profesores Jonathan P. Wojciechowski y Molly M. Stevens, nota realizada en la revista Science, con motivo del artículo publicado por Ivan Sasselli. Revista Science, 374 (6569), • DOI: 10.1126/science.abh3602
Cell wall in plants- introduction, cell wall layers, functions, sugars the building blocks of cell wall, macromolecules of cell wall, cell wall architecture, biosynthesis and assembly
The document summarizes recent findings regarding two Arabidopsis mutants involved in plant cell expansion.
The first mutant is rsw1, which encodes a subunit of cellulose synthase. At restrictive temperatures, rsw1 cells produce non-crystalline glucan instead of cellulose microfibrils. This supports the role of RSW1 in cellulose synthesis.
The second mutant is korrigan, which encodes an unusual endo-1,4-β-glucanase enzyme. kor cells have thick, undulating cell walls that lack the layered microfibril structure of wild-type walls. This suggests KORRIGAN is involved in remodeling of the cell wall during
The document summarizes the composition and architecture of plant cell walls. It discusses the primary components of plant cell walls including cellulose, hemicellulose, pectin and lignin. It describes how these components interact through different proposed models and compares the structure of primary and secondary cell walls. Secondary cell walls are thicker and stronger and contain more lignin, which provides rigidity important for conducting tissues. The recalcitrance of secondary cell walls is important for applications in biofuels and pulp/paper industries.
This document describes a protocol for engineering cardiac tissue using perfusion bioreactor systems. Cardiac cells are seeded onto porous scaffolds and cultured in bioreactors with perfusion of culture medium, which provides oxygen to the cells and overcomes limitations of conventional static culture. Two approaches are discussed: interstitial flow through porous scaffolds and flow through channel arrays in scaffolds. Perfusion improves cell viability, density, and function compared to static culture and enables engineering of thicker cardiac constructs.
The distribution of callose synthase, cellulose synthase, and sucrose synthase in tobacco pollen tubes is controlled by actin filaments and microtubules in different ways. Cellulose synthase is present along the entire length of pollen tubes, with higher concentration at the apex, while callose synthase is located in the apex and around callose plugs. Actin filaments and endomembrane dynamics control the distribution of both enzymes by transporting them via Golgi bodies and vesicles. Microtubules control the positioning of callose synthase in distal regions and around plugs, but only partially influence cellulose synthase distribution. Sucrose synthase binds to actin filaments and provides UDP-
Biomaterial is any matter or construct that interacts with biological systems. Biomaterials are often produced in nature or synthesized in the lab using metallic, ceramic, or chemical approaches. They are used for medical applications like implants and prosthetics. Biomaterials must be biocompatible with the human body. The field of biomaterials science incorporates elements of medicine, biology, chemistry, and materials science to develop these materials.
A recent publication by Dr. Sachin Kadam, CTO of Advancells, sheds light on natural osteoinductive bio-compatible scaffolds for effective clinical applications on musculoskeletal disorders. These scaffolds can enhance the efficiency of stem cell transplantation, and thus improve healthcare manifold.
Los profesores Jonathan P. Wojciechowski y Molly M. Stevens, nota realizada en la revista Science, con motivo del artículo publicado por Ivan Sasselli. Revista Science, 374 (6569), • DOI: 10.1126/science.abh3602
Plant cell walls are composed primarily of cellulose, hemicellulose, and pectin. There are two main types of cell walls - primary walls that surround growing cells and secondary walls that surround cells performing specialized functions. Primary walls are composed of cellulose microfibrils cross-linked with hemicellulose and embedded in a matrix of pectin. Pectin, hemicellulose, and cellulose together give plant cell walls their strength, structure, and ability to regulate processes like cell expansion.
The plant cell wall is a complex structure outside the cell membrane that provides structure and protection to the cell. It is made up of three main layers - the middle lamella, primary cell wall, and secondary cell wall. The primary cell wall is thin and elastic in young cells, and contains cellulose fibrils, hemicellulose, and pectin. As the cell matures, the secondary cell wall is deposited between the primary cell wall and cell contents. It is rigid and made mostly of cellulose and lignin. Together, the cell wall layers strengthen the plant body and play important roles in growth, differentiation, and defense.
The fluid mosaic model proposes that cell membranes are two-dimensional solutions of oriented globular proteins and lipids. The model views membranes as a fluid structure, where proteins and lipids can move laterally within the plane of the membrane. This fluid structure is stabilized by noncovalent interactions between hydrophobic and hydrophilic regions of lipids and proteins. The fluid mosaic model provides a framework for understanding the molecular organization and functions of cell membranes.
Marine mussels secrete adhesive proteins called mussel foot proteins (Mfps) that allow them to strongly attach to surfaces underwater. Mfps contain high amounts of the amino acid 3,4-dihydroxyphenylalanine (Dopa), which allows for crosslinking and binding to surfaces. At least six Mfps have been identified, with Mfp-1 providing a protective coating, Mfp-2 providing structural integrity, and Mfp-3,5,6 contributing to strong wet adhesion. The oxidation state and hydrophobicity of Dopa and other factors contribute to adhesion. Several strategies have been used to synthesize catechol-functionalized polymers, including direct functionalization, polymerization, and recombinant techniques. These biom
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
This document summarizes various methods that have been attempted to modify plant cell walls to make them more amenable to breaking down and extracting glucose. Some key methods discussed include overexpressing genes to increase overall biomass and cellulose concentration, removing undesirable components like hemicellulose through genetic inhibition, introducing soluble polysaccharides to make cellulose more accessible, and degrading lignin through various enzymatic and genetic techniques. The document evaluates the challenges and outcomes of these different cell wall modification approaches.
Biomaterials were defined as “any substance, other than a drug, or a combination of substances, synthetic or natural in origin, which can be used for any period of time, as a whole or as a part of a system, which treats, augments or replaces any tissue, organ or function of the body”
Cellulose Based Materials: in-Depth Property Survey And AssessmentIRJESJOURNAL
Abstract: During the past decade, holistic efforts by academia, industries, and regulatory bodies have resulted in a paradigm shift in the area of cellulose nanomaterials for materials applications. In an effort to reduce the dependence on petroleum-based packaging materials and coatings, groups are employing advanced nano understanding to manufacture materials that can potentially replace these materials. In effect, environmental concerns and resource availability will become the main factors driving the market demand for these products. This review focuses on the properties of cellulose-based nanomaterials and the possible use of these materials in niche applications. The review covers both partially and fully biodegradable inventions covered in the past 10 years (2006-2016) in the literature. Also, where data is available, environmental footprint and cost analysis of these products are presented.
The document discusses plant cell walls and membranes. It provides details on:
- The structure and layers of plant cell walls, including the primary and secondary cell walls.
- The major components and functions of plant cell walls, which provide shape, protection and support to cells.
- How cell walls are permeable and limit the passage of large molecules.
- The structure and components of plasma membranes, including the phospholipid bilayer and integral membrane proteins that perform important functions like transport and signaling.
The document discusses the fluid mosaic model of cell membrane structure. It provides background on early models from the 1930s and discusses the fluid mosaic model proposed by Singer and Nicolson in 1972 which is still widely accepted today. The model proposes that the membrane is a fluid structure with proteins dispersed randomly within the phospholipid bilayer. Some updates to the model include recognition of a high density of transmembrane proteins, membrane curvature, lateral heterogeneity with protein/lipid domains, and transient non-bilayer structures.
This power point presentation consists of 64 slides including information about plant and other type of cell wall. Chemical composition, structure, function and properties of cell wall have been explained. Ultra structure of plant cell wall has also been high lighted. Algal,Fungal,Bacterial and Archaeal cell walls have also been explained.
This document discusses using poly(L-lactic acid) (PLLA) scaffolds for cartilage tissue engineering. PLLA is a suitable scaffold material because it degrades at a rate that allows new tissue to form while providing structural support. A study seeded mesenchymal stem cells onto PLLA scaffolds and found the cells adhered uniformly and differentiated into chondrocytes, expressing cartilage markers and forming extracellular matrix. PLLA scaffolds have advantages like an ideal degradation rate that matches tissue growth and causes less inflammation than other materials. This makes PLLA scaffolds a promising option for cartilage regeneration applications.
The document discusses the production of second-generation biofuels from plant cell walls through deconstruction into simple sugars and fermentation. It describes current barriers to commercial viability including the robust and complex structure of cell walls composed of cellulose, hemicellulose, and lignin. The document examines potential solutions such as genetically modifying plant cell walls to make them more soluble and enzyme accessible, as well as using cellulase enzymes from microorganisms and fungi that can break down cellulose. However, it concludes that overcoming all barriers will require continued research into multiple interrelated areas such as plant genetics, cell wall structure, microorganisms, and pretreatment techniques.
The fluid mosaic model proposes that the cell membrane is composed of a lipid bilayer with embedded proteins that move laterally within the bilayer. Phospholipids form a double layer with their hydrophobic tails pointed inward and hydrophilic heads outward. Proteins are embedded within or attached to either surface of the membrane. Cholesterol is also present within the phospholipid bilayer, where it helps to stabilize the structure. The fluid mosaic model provides a satisfactory structure of the cell membrane and was proposed by Singer and Nicolson in 1972.
This document summarizes a study that investigated the role of ethylene in regulating the trans-differentiation of epidermal cells in Vicia faba (faba bean) cotyledons into transfer cells (TCs) with wall ingrowths. The study found that:
1) Manipulating ethylene biosynthesis and perception affected wall ingrowth formation, indicating ethylene is required to both induce and sustain their development.
2) Ethylene biosynthesis genes were expressed in a spatial and temporal pattern correlated with ethylene production and wall ingrowth induction, preceding their formation.
3) Downstream ethylene signaling components like EIN3 and ERF genes were also differentially expressed
KORRIGAN is identified as the gene responsible for the kor mutant phenotype in Arabidopsis thaliana, which displays severe dwarfism and cell elongation defects. KOR encodes a putative plasma membrane-bound endo-1,4-Î2-D-glucanase. Analysis of the kor mutant suggests KOR plays a central role in the assembly of the cellulose-hemicellulose network in expanding cell walls. KOR mRNA levels correlate with rapid cell elongation and are reduced in a mutant deficient for brassinosteroids, implicating a role for KOR in cell wall remodeling during growth.
Nicol F et al. A plasma membrane-bound putative endo-1, 4-beta-D-glucanase is...Frédéric NICOL, phD
KORRIGAN is identified as the gene responsible for the kor mutant phenotype in Arabidopsis thaliana, which displays severe dwarfism and cell elongation defects. KOR encodes a putative plasma membrane-bound endo-1,4-Î2-D-glucanase. Analysis of the kor mutant suggests KOR plays a central role in the assembly of the cellulose-hemicellulose network in expanding cell walls. KOR mRNA levels correlate with rapid cell elongation and are reduced in a mutant deficient for brassinosteroids, implicating a role for KOR in cell wall remodeling during growth.
This document summarizes key information about plant cell walls. It begins by introducing the topic and providing background on the discovery of cell walls. It then describes the main components of plant cell walls, including the three layers (middle lamella, primary cell wall, and secondary cell wall). The structural organization and chemical composition of cell walls is also summarized. Finally, the main functions of the cell wall in providing structure, protection, and facilitating transport are outlined.
Tissue engineering uses scaffolds, cells, and signaling molecules to regenerate tissues and organs. Scaffolds provide a structure for cell attachment, growth, and tissue formation. Natural polymers like collagen and hyaluronic acid, and synthetic polymers like poly-lactic-co-glycolic acid are commonly used as scaffold materials. Scaffolds can be fabricated using various methods including freeze drying, electrospinning, 3D printing, and textile technologies to produce scaffolds with desirable properties like porosity and pore size for tissue growth. Scaffolds seeded with stem cells or tissue-specific cells aim to repair and regenerate tissues for applications in skin, bone, cartilage, and other organs.
This document discusses tissue engineering principles and their application to periodontal regeneration. It outlines that tissue engineering involves enhancing biologic processes or developing implantable products to modify deficient tissues. For periodontal regeneration specifically, the goal is to restore the original architecture and function of periodontal tissues affected by disease. Various techniques for periodontal regeneration are discussed, including guided tissue regeneration using membranes, root surface conditioning, and use of regenerative materials like ceramics, growth factors, and stem cells. Successful regeneration requires balancing cells, signaling molecules, and scaffolds in both in vitro and in vivo contexts.
El documento habla sobre diferentes métodos para controlar malezas, incluyendo erradicación, control y manejo. La erradicación busca eliminar completamente una maleza específica de una zona, mientras que el control busca reducir o evitar daños de las malezas a los cultivos. El manejo combina medidas de prevención, control y erradicación a largo plazo para minimizar el impacto de las malezas.
“POTENCIAL DE RENDIMIENTO DE LÍNEAS MUTANTES DE ARROZ (Oryza sativa L.) DESAR...lizette89
POTENCIAL DE RENDIMIENTO DE LÍNEAS MUTANTES DE ARROZ (Oryza sativa L.) DESARROLLADAS MEDIANTE APLICACIÓN DE RAYOS GAMMA EN CONDICIONES DEL VALLE DE JEQUETEPEQUE" .pdf
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Plant cell walls are composed primarily of cellulose, hemicellulose, and pectin. There are two main types of cell walls - primary walls that surround growing cells and secondary walls that surround cells performing specialized functions. Primary walls are composed of cellulose microfibrils cross-linked with hemicellulose and embedded in a matrix of pectin. Pectin, hemicellulose, and cellulose together give plant cell walls their strength, structure, and ability to regulate processes like cell expansion.
The plant cell wall is a complex structure outside the cell membrane that provides structure and protection to the cell. It is made up of three main layers - the middle lamella, primary cell wall, and secondary cell wall. The primary cell wall is thin and elastic in young cells, and contains cellulose fibrils, hemicellulose, and pectin. As the cell matures, the secondary cell wall is deposited between the primary cell wall and cell contents. It is rigid and made mostly of cellulose and lignin. Together, the cell wall layers strengthen the plant body and play important roles in growth, differentiation, and defense.
The fluid mosaic model proposes that cell membranes are two-dimensional solutions of oriented globular proteins and lipids. The model views membranes as a fluid structure, where proteins and lipids can move laterally within the plane of the membrane. This fluid structure is stabilized by noncovalent interactions between hydrophobic and hydrophilic regions of lipids and proteins. The fluid mosaic model provides a framework for understanding the molecular organization and functions of cell membranes.
Marine mussels secrete adhesive proteins called mussel foot proteins (Mfps) that allow them to strongly attach to surfaces underwater. Mfps contain high amounts of the amino acid 3,4-dihydroxyphenylalanine (Dopa), which allows for crosslinking and binding to surfaces. At least six Mfps have been identified, with Mfp-1 providing a protective coating, Mfp-2 providing structural integrity, and Mfp-3,5,6 contributing to strong wet adhesion. The oxidation state and hydrophobicity of Dopa and other factors contribute to adhesion. Several strategies have been used to synthesize catechol-functionalized polymers, including direct functionalization, polymerization, and recombinant techniques. These biom
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
This document summarizes various methods that have been attempted to modify plant cell walls to make them more amenable to breaking down and extracting glucose. Some key methods discussed include overexpressing genes to increase overall biomass and cellulose concentration, removing undesirable components like hemicellulose through genetic inhibition, introducing soluble polysaccharides to make cellulose more accessible, and degrading lignin through various enzymatic and genetic techniques. The document evaluates the challenges and outcomes of these different cell wall modification approaches.
Biomaterials were defined as “any substance, other than a drug, or a combination of substances, synthetic or natural in origin, which can be used for any period of time, as a whole or as a part of a system, which treats, augments or replaces any tissue, organ or function of the body”
Cellulose Based Materials: in-Depth Property Survey And AssessmentIRJESJOURNAL
Abstract: During the past decade, holistic efforts by academia, industries, and regulatory bodies have resulted in a paradigm shift in the area of cellulose nanomaterials for materials applications. In an effort to reduce the dependence on petroleum-based packaging materials and coatings, groups are employing advanced nano understanding to manufacture materials that can potentially replace these materials. In effect, environmental concerns and resource availability will become the main factors driving the market demand for these products. This review focuses on the properties of cellulose-based nanomaterials and the possible use of these materials in niche applications. The review covers both partially and fully biodegradable inventions covered in the past 10 years (2006-2016) in the literature. Also, where data is available, environmental footprint and cost analysis of these products are presented.
The document discusses plant cell walls and membranes. It provides details on:
- The structure and layers of plant cell walls, including the primary and secondary cell walls.
- The major components and functions of plant cell walls, which provide shape, protection and support to cells.
- How cell walls are permeable and limit the passage of large molecules.
- The structure and components of plasma membranes, including the phospholipid bilayer and integral membrane proteins that perform important functions like transport and signaling.
The document discusses the fluid mosaic model of cell membrane structure. It provides background on early models from the 1930s and discusses the fluid mosaic model proposed by Singer and Nicolson in 1972 which is still widely accepted today. The model proposes that the membrane is a fluid structure with proteins dispersed randomly within the phospholipid bilayer. Some updates to the model include recognition of a high density of transmembrane proteins, membrane curvature, lateral heterogeneity with protein/lipid domains, and transient non-bilayer structures.
This power point presentation consists of 64 slides including information about plant and other type of cell wall. Chemical composition, structure, function and properties of cell wall have been explained. Ultra structure of plant cell wall has also been high lighted. Algal,Fungal,Bacterial and Archaeal cell walls have also been explained.
This document discusses using poly(L-lactic acid) (PLLA) scaffolds for cartilage tissue engineering. PLLA is a suitable scaffold material because it degrades at a rate that allows new tissue to form while providing structural support. A study seeded mesenchymal stem cells onto PLLA scaffolds and found the cells adhered uniformly and differentiated into chondrocytes, expressing cartilage markers and forming extracellular matrix. PLLA scaffolds have advantages like an ideal degradation rate that matches tissue growth and causes less inflammation than other materials. This makes PLLA scaffolds a promising option for cartilage regeneration applications.
The document discusses the production of second-generation biofuels from plant cell walls through deconstruction into simple sugars and fermentation. It describes current barriers to commercial viability including the robust and complex structure of cell walls composed of cellulose, hemicellulose, and lignin. The document examines potential solutions such as genetically modifying plant cell walls to make them more soluble and enzyme accessible, as well as using cellulase enzymes from microorganisms and fungi that can break down cellulose. However, it concludes that overcoming all barriers will require continued research into multiple interrelated areas such as plant genetics, cell wall structure, microorganisms, and pretreatment techniques.
The fluid mosaic model proposes that the cell membrane is composed of a lipid bilayer with embedded proteins that move laterally within the bilayer. Phospholipids form a double layer with their hydrophobic tails pointed inward and hydrophilic heads outward. Proteins are embedded within or attached to either surface of the membrane. Cholesterol is also present within the phospholipid bilayer, where it helps to stabilize the structure. The fluid mosaic model provides a satisfactory structure of the cell membrane and was proposed by Singer and Nicolson in 1972.
This document summarizes a study that investigated the role of ethylene in regulating the trans-differentiation of epidermal cells in Vicia faba (faba bean) cotyledons into transfer cells (TCs) with wall ingrowths. The study found that:
1) Manipulating ethylene biosynthesis and perception affected wall ingrowth formation, indicating ethylene is required to both induce and sustain their development.
2) Ethylene biosynthesis genes were expressed in a spatial and temporal pattern correlated with ethylene production and wall ingrowth induction, preceding their formation.
3) Downstream ethylene signaling components like EIN3 and ERF genes were also differentially expressed
KORRIGAN is identified as the gene responsible for the kor mutant phenotype in Arabidopsis thaliana, which displays severe dwarfism and cell elongation defects. KOR encodes a putative plasma membrane-bound endo-1,4-Î2-D-glucanase. Analysis of the kor mutant suggests KOR plays a central role in the assembly of the cellulose-hemicellulose network in expanding cell walls. KOR mRNA levels correlate with rapid cell elongation and are reduced in a mutant deficient for brassinosteroids, implicating a role for KOR in cell wall remodeling during growth.
Nicol F et al. A plasma membrane-bound putative endo-1, 4-beta-D-glucanase is...Frédéric NICOL, phD
KORRIGAN is identified as the gene responsible for the kor mutant phenotype in Arabidopsis thaliana, which displays severe dwarfism and cell elongation defects. KOR encodes a putative plasma membrane-bound endo-1,4-Î2-D-glucanase. Analysis of the kor mutant suggests KOR plays a central role in the assembly of the cellulose-hemicellulose network in expanding cell walls. KOR mRNA levels correlate with rapid cell elongation and are reduced in a mutant deficient for brassinosteroids, implicating a role for KOR in cell wall remodeling during growth.
This document summarizes key information about plant cell walls. It begins by introducing the topic and providing background on the discovery of cell walls. It then describes the main components of plant cell walls, including the three layers (middle lamella, primary cell wall, and secondary cell wall). The structural organization and chemical composition of cell walls is also summarized. Finally, the main functions of the cell wall in providing structure, protection, and facilitating transport are outlined.
Tissue engineering uses scaffolds, cells, and signaling molecules to regenerate tissues and organs. Scaffolds provide a structure for cell attachment, growth, and tissue formation. Natural polymers like collagen and hyaluronic acid, and synthetic polymers like poly-lactic-co-glycolic acid are commonly used as scaffold materials. Scaffolds can be fabricated using various methods including freeze drying, electrospinning, 3D printing, and textile technologies to produce scaffolds with desirable properties like porosity and pore size for tissue growth. Scaffolds seeded with stem cells or tissue-specific cells aim to repair and regenerate tissues for applications in skin, bone, cartilage, and other organs.
This document discusses tissue engineering principles and their application to periodontal regeneration. It outlines that tissue engineering involves enhancing biologic processes or developing implantable products to modify deficient tissues. For periodontal regeneration specifically, the goal is to restore the original architecture and function of periodontal tissues affected by disease. Various techniques for periodontal regeneration are discussed, including guided tissue regeneration using membranes, root surface conditioning, and use of regenerative materials like ceramics, growth factors, and stem cells. Successful regeneration requires balancing cells, signaling molecules, and scaffolds in both in vitro and in vivo contexts.
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El documento habla sobre diferentes métodos para controlar malezas, incluyendo erradicación, control y manejo. La erradicación busca eliminar completamente una maleza específica de una zona, mientras que el control busca reducir o evitar daños de las malezas a los cultivos. El manejo combina medidas de prevención, control y erradicación a largo plazo para minimizar el impacto de las malezas.
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Este documento presenta información sobre la medición y el estudio de la biodiversidad. Explica los diferentes enfoques para medir la diversidad alfa, beta y gamma a nivel de comunidades y paisajes. También describe varios índices y métodos para cuantificar la riqueza de especies y la estructura de las comunidades, como los índices de Margalef, Menhinick y Shannon-Wiener. El documento proporciona una visión general completa de los conceptos y herramientas clave para evaluar la biodiversidad.
El documento describe los atributos y procesos que se utilizan para describir una comunidad ecológica. Entre los atributos se encuentran la composición de especies, riqueza, abundancias relativas y diversidad. También se describen la estructura trófica, formas de vida, dominancia y grupos funcionales. Los procesos incluyen las interacciones entre especies, flujos de materia y energía, y dinámicas espaciales y temporales. Finalmente, se explican métodos para medir la diversidad de una comunidad y delimitar las
El documento describe los procesos de nutrición en las plantas. Explica que las plantas obtienen materia y energía a través de la fotosíntesis, absorbiendo agua y minerales por las raíces y transportándolos por el xilema, mientras que los productos de la fotosíntesis se transportan por el floema. También describe los mecanismos de apertura de estomas, fases de la fotosíntesis, respiración celular y eliminación de desechos.
El documento argumenta a favor de ampliar la moratoria a los transgénicos en Perú para proteger la gran biodiversidad del país y fortalecer la seguridad alimentaria. El Perú es un país megadiverso con una gran variedad de recursos agrícolas que se ven amenazados por los transgénicos debido al riesgo de contaminación genética y pérdida de biodiversidad. Los análisis económicos muestran que los cultivos convencionales manejados de manera sostenible son más rentables que los transgénicos
El documento describe las funciones de relación en las plantas, que incluyen captar información del exterior a través de estímulos y elaborar respuestas para adaptarse al medio ambiente. Las plantas carecen de sistema nervioso y no pueden desplazarse, por lo que utilizan fitohormonas como mensajeras para controlar su desarrollo de forma equilibrada y coordinada en respuesta a factores internos como los genes y las hormonas, y externos como la luz, el agua y la temperatura.
Ian_Zelaya-Fisiología Vegetal y Modo Accion Herbicidas.pdflizette89
Las principales diferencias entre monocotiledóneas y dicotiledóneas son:
- Las monocotiledóneas tienen un cotiledón mientras que las dicotiledóneas tienen dos cotiledones.
- Las hojas de las monocotiledóneas tienen nervaduras paralelas mientras que las dicotiledóneas tienen nervaduras laterales.
- Las flores de las monocotiledóneas son simples sin pétalos, mientras que las dicotiledóneas tienen flores más complejas con pétalos y colores variados.
Las malezas se convierten en un problema cuando compiten con los cultivos por recursos como agua, nutrientes y luz; cuando sirven como hospederos de plagas y enfermedades que afectan a los cultivos; y cuando interfieren con las operaciones de cosecha e incrementan los costos de producción. Algunas malezas también pueden liberar compuestos químicos que inhiben el crecimiento de los cultivos. Sin embargo, algunas malezas también proveen beneficios como hábitat para insectos benéficos y contribuyen a la conservación del suelo.
Las monocotiledóneas y dicotiledóneas difieren en varias características clave como el número de cotiledones, la orientación de las venas de las hojas, el sistema radicular, la estructura floral y el sistema vascular. Las monocotiledóneas generalmente tienen un cotiledón, venas paralelas, raíces fibrosas sin raíz pivotante, flores simples sin pétalos y un sistema vascular en forma circular, mientras que las dicotiledóneas tienen dos cotiledones, venas en ángulo, raíces robustas con
Este documento describe la clasificación de malezas de acuerdo a su ciclo de vida, morfología, hábitat y hábito de crecimiento. Las clasifica como anuales, bianuales o perennes y por su morfología como dicotiledóneas de hoja ancha o monocotiledóneas de hoja fina. También las divide según su hábitat en acuáticas sumergidas, flotantes, emergentes o terrestres de berma o talud. Finalmente, las clasifica por su hábito de crecimiento como erectas
Phenomics assisted breeding in crop improvementIshaGoswami9
As the population is increasing and will reach about 9 billion upto 2050. Also due to climate change, it is difficult to meet the food requirement of such a large population. Facing the challenges presented by resource shortages, climate
change, and increasing global population, crop yield and quality need to be improved in a sustainable way over the coming decades. Genetic improvement by breeding is the best way to increase crop productivity. With the rapid progression of functional
genomics, an increasing number of crop genomes have been sequenced and dozens of genes influencing key agronomic traits have been identified. However, current genome sequence information has not been adequately exploited for understanding
the complex characteristics of multiple gene, owing to a lack of crop phenotypic data. Efficient, automatic, and accurate technologies and platforms that can capture phenotypic data that can
be linked to genomics information for crop improvement at all growth stages have become as important as genotyping. Thus,
high-throughput phenotyping has become the major bottleneck restricting crop breeding. Plant phenomics has been defined as the high-throughput, accurate acquisition and analysis of multi-dimensional phenotypes
during crop growing stages at the organism level, including the cell, tissue, organ, individual plant, plot, and field levels. With the rapid development of novel sensors, imaging technology,
and analysis methods, numerous infrastructure platforms have been developed for phenotyping.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
Unlocking the mysteries of reproduction: Exploring fecundity and gonadosomati...AbdullaAlAsif1
The pygmy halfbeak Dermogenys colletei, is known for its viviparous nature, this presents an intriguing case of relatively low fecundity, raising questions about potential compensatory reproductive strategies employed by this species. Our study delves into the examination of fecundity and the Gonadosomatic Index (GSI) in the Pygmy Halfbeak, D. colletei (Meisner, 2001), an intriguing viviparous fish indigenous to Sarawak, Borneo. We hypothesize that the Pygmy halfbeak, D. colletei, may exhibit unique reproductive adaptations to offset its low fecundity, thus enhancing its survival and fitness. To address this, we conducted a comprehensive study utilizing 28 mature female specimens of D. colletei, carefully measuring fecundity and GSI to shed light on the reproductive adaptations of this species. Our findings reveal that D. colletei indeed exhibits low fecundity, with a mean of 16.76 ± 2.01, and a mean GSI of 12.83 ± 1.27, providing crucial insights into the reproductive mechanisms at play in this species. These results underscore the existence of unique reproductive strategies in D. colletei, enabling its adaptation and persistence in Borneo's diverse aquatic ecosystems, and call for further ecological research to elucidate these mechanisms. This study lends to a better understanding of viviparous fish in Borneo and contributes to the broader field of aquatic ecology, enhancing our knowledge of species adaptations to unique ecological challenges.
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
Travis Hills' Endeavors in Minnesota: Fostering Environmental and Economic Pr...Travis Hills MN
Travis Hills of Minnesota developed a method to convert waste into high-value dry fertilizer, significantly enriching soil quality. By providing farmers with a valuable resource derived from waste, Travis Hills helps enhance farm profitability while promoting environmental stewardship. Travis Hills' sustainable practices lead to cost savings and increased revenue for farmers by improving resource efficiency and reducing waste.
hematic appreciation test is a psychological assessment tool used to measure an individual's appreciation and understanding of specific themes or topics. This test helps to evaluate an individual's ability to connect different ideas and concepts within a given theme, as well as their overall comprehension and interpretation skills. The results of the test can provide valuable insights into an individual's cognitive abilities, creativity, and critical thinking skills
2. cell walls need to be strong enough to prevent the cells from
bursting, yet sufficiently flexible to steer plant cell expansion.
Whereas the contents of plant cell walls differ from those of fungi
and animals, certain functional aspects are similar. This includes
roles in cell protection, cell-to-cell communication, and cell
adhesion and proliferation (Free, 2013; Hynes, 2009; Tsang et al.,
2010).
All growing plant cells are surrounded by a thin, highly hydrated
and flexible primary wall. In dicotyledons such as Arabidopsis
thaliana, this wall type typically consists of a framework of
cellulose microfibrils that are cross-linked to each other by branched
polysaccharides, which are referred to as hemicelluloses and pectins
(Ivakov and Persson, 2012) (see poster). In some plant cells, such as
those found in the tracheary elements and fibers in the xylem, a
secondary cell wall is deposited inside of the primary wall. The
major constituent of the secondary cell wall is cellulose, which is
cross-linked by hemicellulosic polymers (Thornber and Northcote,
1962). Hydrophobic lignin is also deposited throughout the
secondary walls, which results in dehydration of the wall
compartment (Cesarino et al., 2016; Marriott et al., 2016). This
composition increases the strength of the walls and reduces their
flexibility, allowing the resulting tube-like structure to serve as
water conduits and as the mechanical or structural support for the
plant. Here, we highlight how cell wall components are synthesized
and their subsequent integration into the plant primary cell wall.
An inventory of the plant cell wall polysaccharides
Cellulose and callose
Cellulose is a linear homopolysaccharide that is composed of
repeating glucose residues linked by β(1,4)-bonds that make up long
and rigid microfibrils and thus are the load-bearing structures in
the walls. These microfibrils form the scaffold of the cell wall,
and become interconnected by hemicelluloses and pectins
(Nishiyama, 2009; Wang et al., 2012). Callose too is a linear
homopolysaccharide composed of glucose residues; however, rather
than being linked through β(1,4)-bonds, callose is made up of β
(1,3)-linkages. Under normal growth conditions, callose is
generally only found in specialized cells, such as tip growing
cells, pollen tubes or stomata, and at specific cell compartments,
such as the plasmodesmata, or as a transient component of cell
plates in dividing cells (Schneider et al., 2016). Callose synthesis
may also occur at the wall in response to abiotic or biotic stress
(Nielsen et al., 2012). Callose typically functions as a regional wall
stabilizer (e.g. at pathogen entrance points) and modulates
plasmodesmata pore size (De Storme and Geelen, 2014).
Pectins
Pectins are a diverse and highly complex class of polysaccharides
that are enriched in galacturonic acid (GalA) (Harholt et al., 2010).
For example, homogalacturonan (HG) and rhamnogalacturonan
(RG)II have backbones consisting of α(1,4)-GalA, whereas
the backbone of the other RG polymer, RG-I, consists of a
repeated motif of α(1,4)-GalA and α(1,2)-rhamnose. These
backbones can be decorated with an array of oligosaccharides,
such as α(l,5)-arabinans and β(1,4)-galactans, and complex
heteropolysaccharides, as well as with methyl and acetyl groups.
HGs are transported to the wall in highly esterified forms but
become selectively de-esterified, which mediates polymer cross-
linking through Ca2+
. RG-II may also be cross-linked by boron ions
(B3+
); together, these links might rigidify the wall matrix. Pectic
polysaccharides can also be linked to glycoproteins and other cell
wall carbohydrates that may further stabilize the wall structure (Tan
et al., 2013). Hence, pectins can control cell wall flexibility, and are
thus important for cell proliferation and plant growth (Peaucelle
et al., 2012).
Hemicelluloses
The most common hemicelluloses in cell walls of the plant model
organism Arabidopsis are xyloglucans (XyGs) and xylans. The
XyG backbone is composed of β(1,4)-linked glucose residues that
have α(1,6)-linked xylosyl side chains. These side chains in turn can
be further decorated with galactose – and sometimes fucose –
residues to create complex levels of branches and patterns. The
backbone of xylan is composed of β(1,4)-linked xylose residues
which can be decorated with, for example, glucuronic acid to
produce glucuroxylan (Pauly et al., 2013). Both XyGs and xylans
may also be modified by acetylation, which affects their capacity to
cross-link to other cell wall components (Zhang et al., 2017). XyG is
the main hemicellulose in dicot primary walls, and most likely
functions to cross-link cellulose microfibrils (Park and Cosgrove,
2015). While the initial assumption was that the cellulose
microfibrils were coated with xyloglucans, which would then
interact to cross-link the microfibrils, more recent data indicate that
the xyloglucan–cellulose interaction is limited to distinct regions
along the microfibril, referred to as hotspots, that are important to
convey biomechanical stability to the wall (Park and Cosgrove,
2015). Although xylans are major hemicelluloses in secondary cell
walls, they are also prominent in primary walls of monocots and
some algae. Similar to XyGs in primary walls, xylans can also
cross-link cellulose microfibrils (Simmons et al., 2016).
Assembly of the cell wall polysaccharides
Cell wall polysaccharides are composed of monosaccharide
residues linked through an array of glycosidic linkages. Assembly
of these subunits requires the repeated addition of single sugar
residues that are provided in an activated form of nucleoside
diphosphate (NDP)-sugars. Whereas most of these activated sugars
are produced in the cytosol, the synthesis of pectins and
hemicelluloses occurs in the Golgi; furthermore, the active sites
of the glycosyltransferases (GTs) often face the Golgi lumen. Some
activated sugars must therefore be transported into the lumen of the
Golgi or endoplasmic reticulum (ER), where they are added to
specific polysaccharide acceptors by the corresponding GTs. This
transport is facilitated by nucleotide sugar transporters (NSTs),
which are antiporters that exchange nucleoside monophosphate for
specific NDP-sugars (Temple et al., 2016) (see poster). NSTs are
generally highly substrate specific and, therefore, the Arabidopsis
NST family has more than 40 putative members. The designation of
NST function has seen a major leap forwards in recent years, and
specific NSTs have been assigned for GDP-mannose, UDP-
galactose, UDP-glucose, UDP-arabinose and other NDP-sugars
(Orellana et al., 2016; Rautengarten et al., 2017).
The enzymes that act on carbohydrates are known as
carbohydrate active enzymes (CAZYs; http://www.cazy.org).
CAZYs are clustered into four main groups: GTs, glycosyl
hydrolases, polysaccharide lyases and carbohydrate esterases,
which is based on genomic, structural and/or biochemical
information (Cantarel et al., 2009). Here, the largest group by far
comprises the GTs, of which there are more than 100 families.
Homology within and between GT families is intrinsically low, as
most GTs produce specific types of glycosidic linkages. Plant
cell wall-related GTs are broadly grouped into two types. The first
(type I) consists of enzymes that catalyze the processive addition of
glycosyl residues such that they do not release the polymer product,
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3. which allows for very high polymerization efficiencies. These are
typically integral membrane proteins that synthesize homo-
polysaccharides, such as β(1,4)-D-glucan (cellulose) or β(1,3)-D-
glucan (callose). In contrast, type II GTs catalyze only a single
transfer after which the enzyme–product complex dissociates. The
type II GTs generally share a common topology that consists of a
short N-terminal cytoplasmic domain, a single transmembrane
domain and a large catalytic domain facing the Golgi lumen. As an
example, biosynthesis of XyG chains requires the activity of one
type I GT, cellulose synthase-like C4, to create the β(1,4)-glucose
backbone, whereas a variety of type II GTs act as
xylosyltransferases, galactosyltransferases and fucosyltransferases
to add the different side chains (Schultink et al., 2014; Pauly and
Keegstra, 2016) (see poster).
In contrast to the aforementioned polymers, callose is not
synthesized in the Golgi but rather at the plasma membrane by
callose synthases or glucan synthase-like (GSL) proteins. The
Arabidopsis genome encodes 12 GSL genes (Verma and Hong,
2001). Consistent with callose production occurring only in
specialized cells and in response to environmental stimuli, GSL
genes are expressed in a tissue-specific fashion. Here, GSL1, GSL2,
GSL6, GSL8 and GSL10 contribute to fertility through pollen
development and cell division, and GSL5, GSL7 and GSL12
provide structural reinforcement to the cell wall (Verma and Hong,
2001). The GSL proteins can interact with a number of ancillary
proteins that include those that are involved in potential substrate
supply, for example sucrose synthase, and those that control
secretion and localization, such as Rho-of-plant 1 and the GTPase
RabA4c (Ellinger and Voigt, 2014; Nedukha, 2015).
Cellulose is also synthesized at the plasma membrane by a
symmetrical cluster or ‘rosette’ of six particles called the cellulose
synthase (CESA) complex (CSC; Somerville et al., 2004) (see
poster). First detected through freeze fracture microscopy in maize,
the current view is that each of the six subunits of the rosette contain
12 to 36 CESA proteins (Nixon et al., 2016; Guerriero et al., 2010).
Arabidopsis has ten structurally similar CESA isoforms (CESA 1 to
10). Current evidence supports the view that both the CSCs of the
primary and secondary wall contain three CESA isoforms: the CSC
of the primary wall contains CESA 1, CESA 3 and CESA 6-like
proteins, and the CSC of the secondary wall contains the CESAs 4, 7
and 8 (Desprez et al., 2007; Persson et al., 2007). Both show
equimolar stoichiometry of the CESA subunits (Gonneau et al.,
2014; Hill et al., 2014), and the GSLs and the CESAs utilize UDP-
glucose as substrate. A major route of UDP-glucose production is
through the cleavage of sucrose by sucrose synthases or by UDP-
glucose pyrophosphorylase and cytosolic invertases (Fujii et al.,
2010; Rende et al., 2017; Verbančič et al., 2017). Sucrose synthases
that are associated with the plasma membrane might channel UDP-
glucose to the CESAs, although it does not seem likely that this
occurs in Arabidopsis (Barratt et al., 2009; Chourey et al., 1998;
Coleman et al., 2009). Mutations in two cytosolic invertases in
Arabidopsis lead to dwarfism, which is thought to be a consequence
of defects in cell wall synthesis (Barratt et al., 2009), a hypothesis
that is supported by analyses in poplar (Rende et al., 2017). Hence,
the substrate supply pathway for callose and cellulose synthesis
remains to be firmly established.
From the inside to the outside – polysaccharide secretion
Both the Golgi-assembled polysaccharides and the protein
complexes that are to become active at the plasma membrane
need to be secreted to the cell surface. Indeed, the secretion of
polysaccharides has been illustrated in experiments using an
alkynylated fucose analog that was incorporated into pectins
during their synthesis in the Golgi, and subsequently could be
detected in the cell wall through click-chemistry (Anderson et al.,
2012). Polysaccharide secretion may occur either through
conventional or unconventional routes. Here, we refer to
conventional protein secretion as vesicles that are generated
through coats (i.e. clathrin and the COPs), which progress via the
trans-Golgi network (TGN) and fuse to target membranes through
traditional tethering factors (Kanazawa and Ueda, 2017). Whereas
the mechanisms underlying the secretion of cell wall polymers
remain largely unknown, some of it has been shown to be controlled
by a protein complex composed of ECHIDNA (ECH) and the YPT/
RAB GTPase-interacting proteins, YIP4a and YIP4b. This pathway
appears to be crucial for both secretion of XyGs and pectins, and
occurs through the TGN (Gendre et al., 2011, 2013) (see poster).
Although many polysaccharides are believed to be produced by
large enzyme complexes, the configurations and assembly
mechanisms of these remain largely elusive. Nevertheless, some
recent studies have demonstrated that several enzymes that are
involved in the production of XyGs, HGs or xylans can interact and
have proposed that these may constitute catalytically active
multiprotein complexes in the Golgi (Atmodjo et al., 2013; Chou
et al., 2015; Zeng et al., 2016).
Several so-called unconventional secretory pathways have also
been implicated in polysaccharide secretion, such as a pathway
involving the exocyst-positive organelle (EXPO), which is
hypothesized to function as a large organelle that is encased by a
double membrane (Wang et al., 2010) (see poster). EXPO is thought
to be formed in the cytosol, possibly emanating from the ER, where
it can sequester proteins and perhaps other material destined for the
apoplast. The outer EXPO membrane is then thought to fuse with
the plasma membrane and a compartment with a single membrane is
then delivered to the apoplast (Ding et al., 2012). The EXPO has
been suggested to play a role in pathogen defense, where it might
transport cell wall material to the apoplast to reinforce the wall in
response to an attack (Pečenková et al., 2011). Nevertheless, more
evidence to support the function and formation of EXPOs is needed.
Callose has been detected in multivesicular bodies (MVBs),
which are specialized endosomes; this suggests that GSLs could be
targeted to the plasma membrane through a pathway that occurs via
this organelle (Cui and Lee, 2016; Xu and Mendgen, 1994).
Another type of vesicles that appears to be specific to the transport
of CESAs are a population of small cytosolic CESA compartments
that are referred to as small CESA-containing vesicles (smaCCs;
Crowell et al., 2009; Gutierrez et al., 2009). These compartments
interact with the cytoskeleton and are thought to be involved in the
cycling of the CSC to and from the plasma membrane (see poster).
The CSC is assembled in the endomembrane system and this
process is aided by Golgi-localized STELLO (STL) proteins. STLs
can interact with and regulate the distribution of CESAs in the
Golgi, and so control the secretion of CSCs (Zhang et al., 2016) (see
poster). The secretion of the CSCs is presumably facilitated through
secretory vesicles that are associated with the tethering factor
SYP61, as this SYP associates with vesicles that also contain
primary wall CESAs (Drakakaki et al., 2012). Efficient secretion of
CSCs also appears to depend on the pH of the endomembranes, the
actin cytoskeleton, phosphoinositide levels and kinesin-related
activities (Fujimoto et al., 2015; Luo et al., 2015; Sampathkumar
et al., 2013; Zhu et al., 2015). Interestingly, the sugar status of the
plant may also regulate the trafficking of CSCs (Ivakov et al., 2017).
Similar to CSCs, it is likely that GSL complexes are also assembled
in the ER or Golgi, and trafficked to the plasma membrane through
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4. the TGN (Cai et al., 2011). Indeed, GSLs are secreted to infection
sites at the plasma membrane through a RabA4c-related pathway
during pathogen infection (Ellinger et al., 2013).
Wall incorporation and modification of the polysaccharides
Activation of the CSCs and GSLs is thought to occur after their
integration into the plasma membrane, although the exact
mechanism is unknown. One possibility is that the activation is
achieved through phosphorylation, as this affects the catalytic
activity of CSCs (Chen et al., 2010; Sánchez-Rodríguez et al.,
2017). It is assumed that the cellulose microfibrils become
entangled in the wall structure and the catalytic activity of the
CESAs therefore drives the CSCs forward through the membrane.
Fluorescently tagged CESAs have been observed to move along
linear trajectories at the plasma membrane (Paredez et al., 2006).
This movement is typically directed by cortical microtubules, both
during primary and secondary wall synthesis, with these
microtubules serving as intracellular ‘rails’ on which the enzyme
complexes can track along (Paredez et al., 2006; Watanabe et al.,
2015). Several proteins have been implicated in connecting CSCs to
the cortical microtubules: these include the CELLULOSE
SYNTHASE-INTERACTING 1, COMPANIONS OF
CELLULOSE SYNTHASE and CELLULOSE SYNTHASE–
MICROTUBULE UNCOUPLING (CMU) proteins (Bringmann
et al., 2012; Endler et al., 2015, 2016; Gu et al., 2010; Li et al., 2012;
Liu et al., 2016) (see poster). These proteins appear to either aid in
maintaining the CSC link to microtubules or to sustain microtubule
positions during cellulose synthesis. Although not as well studied,
GSLs may also colocalize with cortical microtubules; however, it is
unclear whether the GSLs move and if any such movement is also
guided by cortical microtubules (Cai et al., 2011).
The cellulose microfibrils are the load-bearing structures in the
wall and the organization of these therefore determines the direction
of the turgor-driven cell expansion. Hence, transversely organized
cortical microtubules, and thus cellulose fibers, would lead to a
predominantly longitudinal cell expansion (Baskin, 2005;
Sugimoto et al., 2000). Newly secreted pectic polymers have been
observed to be incorporated at sites that co-occur with cellulose
microfibrils, which suggests that cellulose might indeed provide a
scaffold for the addition of other cell wall polysaccharides
(Anderson et al., 2012).
Several protein families can modify cell wall polymers, or the
links between them, after they have been incorporated into the cell
wall. Perhaps the best studied is the family of expansins (EXPs).
Although no clear enzymatic function has been attributed to EXPs,
they have been suggested to modify the interactions between XyGs
and cellulose in a pH-dependent manner, which presumably is the
mechanism underlying the acid-growth hypothesis, which
postulates that cell walls are able to expand at an acidic pH
(Cosgrove, 2005). Thus, low pH activates EXPs, which results in
wall relaxation, thereby allowing wall creep and access to the wall
structure for other wall-modifying proteins (Cosgrove, 2005). One
such group of proteins is the xyloglucan endo-transglycosylases/
hydrolases (XTHs), which can cleave and re-ligate XyG backbones,
thereby possibly incorporating new XyG fragments into the wall
(Eklöf and Brumer, 2010). It is hypothesized that the sites of XTH
activity are determined by the cellulose framework, as some XTHs
can act specifically on XyG–cellulose contact sites (Vissenberg
et al., 2005) (see poster).
The pectin matrix can also be modified by a combination of
several activities, including its cleavage by pectate lyases and/or
through enzyme-independent loosening by reactive oxygen radicals
that occur in the apoplastic space; this aids in re-arranging the matrix
(Chen and Schopfer, 1999; Domingo et al., 1998; Marín-Rodríguez
et al., 2002). Other proteins that contribute to pectin modifications
are the polygalacturonases and pectinmethylesterases (Caffall
and Mohnen, 2009). Polygalacturonases also influence wall
strength by degrading HGs (Atkinson et al., 2002). Consequently,
overexpression of different polygalacturonases typically results in
reduced levels of HG and a reduction in wall stability (Atkinson
et al., 2002; Capodicasa et al., 2004). Pectin methylesterases can
demethylesterify HGs; this impacts on cell wall elasticity as this
modification is one of the prerequisites for the cross-linking of
HGs to other pectic polysaccharides and cell wall proteins (Caffall
and Mohnen, 2009). Pectin methylesterases are counteracted
by pectin methylesterase inhibitors, which promote pectin
methylesterification and thus wall loosening (Caffall and Mohnen,
2009). However, it has been demonstrated that decreased wall
elasticity correlates with demethylesterification, which would
indicate that pectinmethylesterase activity can also promote wall
loosening (Peaucelle et al., 2011). This complex interplay between
different enzymes of opposing functions works to fine-tune wall
expansion and cell growth, while at the same time providing
structural support and mechanical stability – a common theme in
plant cell wall construction and regulation.
The status of the cell wall is thought to be monitored by proteins
that sense wall integrity (Wolf, 2017). These include receptor-like
kinase proteins, such as FERONIA, and its close homolog
THESEUS1, and several wall-associated kinases (WAKs) that
respond to changes in the cell wall architecture (Hématy et al., 2007;
Li et al., 2016; Yeats et al., 2016). The receptor kinase MALE
DISCOVERER 1-INTERACTING RECEPTOR LIKE KINASE 2
may also have a similar function as it is important to convey
cellulose deficiencies in the wall to the cell (Van der Does et al.,
2017). A direct link to cell wall components has been demonstrated
for the WAKs that can bind to pectins and it is plausible that
they therefore recognize and respond to changes in the pectin
polymers (Decreux and Messiaen, 2005; Kohorn and Kohorn,
2012). Another protein involved in sensing changes to the pectic
network is the receptor-like protein 44 that, in concert with BRI1-
ASSOCIATED KINASE 1, triggers responses to impaired pectin
demethylesterification (Wolf et al., 2014). Whereas several
components that sense wall integrity have therefore been
identified, it is clear that a plethora of internal and external cues
that affect the cell wall need to be communicated to the cell to ensure
precise responses. Hence, this is an emerging field that holds high
future potential in plant cell wall biology.
Conclusions and perspectives
Although the past decades have seen a major boost in cell wall
research, many specific areas remain ill defined. For example, much
of our understanding relies on data from tissues rather than specific
cell types, and there is therefore an underappreciation for cell-type-
specific synthesis and modification of cell wall structures. In
addition, a growing number of protein complexes – or perhaps
super-complexes – have been found to be involved in cell wall
synthesis. Further analyses of these complexes and their sub-
compartmentalization will certainly aid in our understanding of how
and where cell wall carbohydrates are made. Finally, the
coordination of synthesis and secretion of polysaccharides
and/or plasma-membrane and apoplastic enzymes is an important
and growing topic that should reveal how compartments
communicate with each other to modulate the overall architecture
of the cell wall.
4
CELL SCIENCE AT A GLANCE Journal of Cell Science (2018) 131, jcs207373. doi:10.1242/jcs.207373
Journal
of
Cell
Science
5. Acknowledgements
We thank Drs Berit Ebert and Heather Mcfarlane for critical reading of the
manuscript.
Funding
S.P. and E.R.L. acknowledge the support of an Australian Research Council
(ARC) Future Fellowship (FT160100218), an ARC Discovery Project grant
(DP150103495), and The Hermon Slade Foundation (research grant HSF 15/4 to
S.P.). G.A.K. acknowledges the support from a Schweizerischer Nationalfonds zur
Fo
̈ rderung der Wissenschaftlichen Forschung early postdoc mobility fellowship
under the grant number P2LAP3_168408. M.S. is funded through a postdoctoral
fellowship by the Deutsche Forschungsgemeinschaft (344523413).
Cell science at a glance
A high-resolution version of the poster and individual poster panels are available
for downloading at http://jcs.biologists.org/lookup/doi/10.1242/jcs.207373.
supplemental
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CELL SCIENCE AT A GLANCE Journal of Cell Science (2018) 131, jcs207373. doi:10.1242/jcs.207373
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