Genomics is impacting agriculture by enabling the study of plant biology on a global scale through genome sequencing and gene expression profiling. Gene expression profiling using microarrays has identified hundreds of genes that are differentially expressed in response to stresses important for agriculture like drought, salt, disease and insects. Proteomics using 2D gel electrophoresis has characterized stress response proteins and been used as a diagnostic tool in plant breeding by identifying protein polymorphisms that are genetic markers or linked to quantitative trait loci (QTLs) controlling traits like drought response.
Identification and expression analysis of LEA gene family members in cucumber...asdasdas19
LEA (late embryogenesis abundant) proteins
are firstly discovered in seeds and then identified in vegetative tissues of different plant species. They are mainly
regulated under abiotic stress conditions. Although genome
wide studies of different gene family members have been
performed in cucumber, there is no such a study for LEA
genes. We have identified 79 LEA genes in the cucumber
genome. Based on phylogenetic analysis, CsLEA genes
could be classified into seven groups in which structural
motifs are relatively conserved. Tandem duplications play
an important role in cucumber genome for LEA gene
expansion. Orthologous and chromosomal relationships of
CsLEA genes were observed based on comparative mapping analysis with other species. The in silico micro-RNA
(miRNA) target analyses indicated that 37 CsLEA genes
were targeted by different miRNAs, especially mir854 and
mir414 are the most abundant identified ones. Public
available RNA-seq data were analyzed for expression
analysis of CsLEA genes in different tissues of cucumber
Understanding the origin and evolution of the eukaryotic cell and the full diversity of eukaryotes is relevant to many biological disciplines.
However, our current understanding of eukaryotic genomes is extremely biased, leading to a skewed view of eukaryotic biology.
We argue that a phylogeny-driven initiative to cover the full eukaryotic diversity is needed to overcome this bias.
•
◦There is an important bias in eukaryotic knowledge, affecting cultures and genomes.
Eukaryotic genomics are biased towards multicellular organisms and their parasites.
◦A phylogeny-driven initiative is needed to overcome the eukaryotic genomic bias.
◦We propose to sequence neglected cultures and increase culturing efforts.
◦Single-cell genomics should be embraced as a tool to explore eukaryotic diversity
Identification and expression analysis of LEA gene family members in cucumber...asdasdas19
LEA (late embryogenesis abundant) proteins
are firstly discovered in seeds and then identified in vegetative tissues of different plant species. They are mainly
regulated under abiotic stress conditions. Although genome
wide studies of different gene family members have been
performed in cucumber, there is no such a study for LEA
genes. We have identified 79 LEA genes in the cucumber
genome. Based on phylogenetic analysis, CsLEA genes
could be classified into seven groups in which structural
motifs are relatively conserved. Tandem duplications play
an important role in cucumber genome for LEA gene
expansion. Orthologous and chromosomal relationships of
CsLEA genes were observed based on comparative mapping analysis with other species. The in silico micro-RNA
(miRNA) target analyses indicated that 37 CsLEA genes
were targeted by different miRNAs, especially mir854 and
mir414 are the most abundant identified ones. Public
available RNA-seq data were analyzed for expression
analysis of CsLEA genes in different tissues of cucumber
Understanding the origin and evolution of the eukaryotic cell and the full diversity of eukaryotes is relevant to many biological disciplines.
However, our current understanding of eukaryotic genomes is extremely biased, leading to a skewed view of eukaryotic biology.
We argue that a phylogeny-driven initiative to cover the full eukaryotic diversity is needed to overcome this bias.
•
◦There is an important bias in eukaryotic knowledge, affecting cultures and genomes.
Eukaryotic genomics are biased towards multicellular organisms and their parasites.
◦A phylogeny-driven initiative is needed to overcome the eukaryotic genomic bias.
◦We propose to sequence neglected cultures and increase culturing efforts.
◦Single-cell genomics should be embraced as a tool to explore eukaryotic diversity
Proteomic analysis of the interaction between the plant growth promoting fhiz...kys9723331
Plant growth-promoting rhizobacteria (PGPR) facilitate the plant growth and enhance their
induced systemic resistance (ISR) against a variety of environmental stresses. In this study,
we carried out integrative analyses on the proteome, transcriptome, and metabolome to investigate
Arabidopsis root and shoot responses to the well-known PGPR strain Paenibacillus
polymyxa (P. polymyxa) E681. Shoot fresh and root dry weights were increased, whereas root
length was decreased by treatment with P. polymyxa E681. 2DE approach in conjunction
with MALDI-TOF/TOF analysis revealed a total of 41 (17 spots in root, 24 spots in shoot)
that were differentially expressed in response to P. polymyxa E681. Biological process- and
molecular function-based bioinformatics analysis resulted in their classification into seven different
protein groups. Of these, 36 proteins including amino acid metabolism, antioxidant,
defense and stress response, photosynthesis, and plant hormone-related proteins were upregulated,
whereas five proteins including three carbohydrate metabolism- and one amino
acid metabolism-related, and one unknown protein were down-regulated, respectively. A good
correlation was observed between protein and transcript abundances for the 12 differentially
expressed proteins during interactions as determined by qPCR analysis. Metabolite analysis
using LC-MS/MS revealed highly increased levels of tryptophan, indole-3-acetonitrile (IAN),
indole-3-acetic acid (IAA), and camalexin in the treated plants. Arabidopsis plant inoculated
P. polymyxa E681 also showed resistance to Botrytis cinerea infection. Taken together these
results suggest that P. polymyxa E681 may promote plant growth by induced metabolism and
activation of defense-related proteins against fungal pathogen.
A number of developments have been made in the molecular biology of oat (Avena spp.) in recent years. Many of these were recently described at the Fourth International Oat Conference, held on 18 to 23 October, in Adelaide, South Australia. These advances include a report of oat transformation and regeneration, the characterisation of J3-glucanase genes in oat, the further development of a molecular genetic map in oats, and the characterisation of genes encoding novel oat grain proteins. A technique for assessing pedigrees in the oat and other cereal crops has been reported using a modified electrophoretic technique.
Abstract— Storage roots are important for the growth and development in plants because they provide nutrients, water, and energy storage. Storage roots are also modulating growth direction, disease resistance, and root formation at the cellular and molecular level through interactions of genes and gene networks. However, molecular mechanisms regulating storage root formation in plants are not fully understood. In this review, we have overviewed transcriptional regulation of storage root formation, proteomic regulation of storage root formation, ethylene regulation of storage root formation, auxin regulation of storage root formation, gene expression regulation of storage root formation, and metabolism regulation of storage root formation. We have reviewed the basic regulatory principles of storage root formation from the network of genomics to proteomics and metabolism in plants that will be valuable to research work in storage root growth and development regulation at the molecular level.
Research on Trivedi Effect -Impact of Biofield Treatment on Growth and Yield ...john henrry
Research done by Mahendra Trivedi - This study tested the impact of Trivedi Effect applied to lettuce and tomato seeds and transplants in commercial plantings with and without fertilizers and pesticides, in relation to yield, quality, and pest inhibition.to read research visit http://www.academicroom.com/article/impact-biofield-treatment-growth-and-yield-lettuce-and-tomato
Research on Trivedi Effect -Impact of Biofield Treatment on Growth and Yield ...Abby Keif
Research done by Mahendra Trivedi - This study tested the impact of Trivedi Effect applied to lettuce and tomato seeds and transplants in commercial plantings with and without fertilizers and pesticides, in relation to yield, quality, and pest inhibition. Read Complete research at: http://works.bepress.com/mahendra_trivedi/1/
Antioxidant activity, photosynthetic rate, and Spectral mass in bean Plants (...IJEABJ
An increase in antioxidant activity is a common response in plants as a defense mechanism against biotic and abiotic stress factors, such response is also generated with the exogenous application of "defense activators", which have negative effects on plant metabolism. In this work, bean plants (Phaseolus vulgaris L.) cv. Pinto Nacional were treated with jasmonic acid (0.5 mM), salicylic acid (2 mM), Trichoderma asperellum (105 spores/ml), and Bacillus pumilus (105 CFU / mL), in order to determine the level of structural and metabolic response of the plants. On the seventh day after the application of the treatments, it was measured the enzymatic activity of catalase (CAT), peroxidase (POX), and superoxide dismutase (SOD). In addition, leaf impressions were taken to measure the stomatal opening and conductance, photosynthetic rate, and the mass spectrum (mass/charge, m/z). The antioxidant activity increased in plants treated with jasmonic acid and T. asperellum, which in turn significantly increased the stomatal opening and conductance, and photosynthetic rate. The mass profile showed that the plants treated with T. asperellum have a greater quantity of masses/charge, of which some had statistically highly significant difference according to the means test Tukey (p <0.05). It is concluded that some defense activators such as jasmonic acid and T. asperellum increase the antioxidant activity, defense response that concurs with the high photosynthetic and metabolic rate in bean plants.
Genetic variability and phylogenetic relationships studies of Aegilops L. usi...Innspub Net
Studying of genetic relationships among Aegilops L. species is very important for broadening the cultivated wheat genepool, and monitoring genetic erosion, because the genus Aegilops includes the wild relatives of cultivated wheat which contain numerous unique alleles that are absent in modern wheat cultivars and it can contribute to broaden the genetic base of wheat and improve yield, quality and resistance to biotic and abiotic stresses of wheat. The use of molecular markers, revealing polymorphism at the DNA level, has been playing an increasing part in plant biotechnology and their genetics studies. There are different types of markers, morphological, biochemical and DNA based molecular markers. These DNA-based markers based on PCR (RAPD, AFLP, SSR, ISSR, IRAP), amongst others, the microsatellite DNA marker has been the most widely used, due to its easy use by simple PCR, followed by a denaturing gel electrophoresis for allele size determination, and to the high degree of information provided by its large number of alleles per locus. Day by day development of such new and specific types of markers makes their importance in understanding the genomic variability and the diversity between the same as well as different species of the plants. In this review, we will discuss about genetic variability and phylogenetic relationships studies of Aegilops L. using some molecular markers, with theirs Advantages, and disadvantages.
Presentation from the International Life Sciences Institute, India - "Scientific Workshop on Safety Assessment of GM Foods" held on 14-15 October, 2015 in New Delhi, India
Breeding for Development of Climate Resilient Chickpea.pptxKanshouwaModunshim
The breeding for the development of Climate Resilient Chickpea is a critical initiative aimed at enhancing the productivity and adaptability of chickpea genotypes under challenging environmental conditions. Chickpea, a vital pulse crop globally, faces yield limitations due to the combined impact of heat, cold, drought, and salinity stresses. The average yields, currently far below the potential, necessitate the development of highly productive and resilient chickpea cultivars. Traditional breeding methods and modern genomic resources, including molecular markers, genetic maps, and QTL identification, have been instrumental in enhancing grain yields and stress adaptation. Marker-assisted backcrossing has successfully produced cultivars like Pusa Manav, demonstrating the effectiveness of genomic technologies. Additionally, the adoption of gene-editing technologies, such as CRISPR-Cas9, holds promise in accelerating genetic gain for stress-related traits.
Proteomic analysis of the interaction between the plant growth promoting fhiz...kys9723331
Plant growth-promoting rhizobacteria (PGPR) facilitate the plant growth and enhance their
induced systemic resistance (ISR) against a variety of environmental stresses. In this study,
we carried out integrative analyses on the proteome, transcriptome, and metabolome to investigate
Arabidopsis root and shoot responses to the well-known PGPR strain Paenibacillus
polymyxa (P. polymyxa) E681. Shoot fresh and root dry weights were increased, whereas root
length was decreased by treatment with P. polymyxa E681. 2DE approach in conjunction
with MALDI-TOF/TOF analysis revealed a total of 41 (17 spots in root, 24 spots in shoot)
that were differentially expressed in response to P. polymyxa E681. Biological process- and
molecular function-based bioinformatics analysis resulted in their classification into seven different
protein groups. Of these, 36 proteins including amino acid metabolism, antioxidant,
defense and stress response, photosynthesis, and plant hormone-related proteins were upregulated,
whereas five proteins including three carbohydrate metabolism- and one amino
acid metabolism-related, and one unknown protein were down-regulated, respectively. A good
correlation was observed between protein and transcript abundances for the 12 differentially
expressed proteins during interactions as determined by qPCR analysis. Metabolite analysis
using LC-MS/MS revealed highly increased levels of tryptophan, indole-3-acetonitrile (IAN),
indole-3-acetic acid (IAA), and camalexin in the treated plants. Arabidopsis plant inoculated
P. polymyxa E681 also showed resistance to Botrytis cinerea infection. Taken together these
results suggest that P. polymyxa E681 may promote plant growth by induced metabolism and
activation of defense-related proteins against fungal pathogen.
A number of developments have been made in the molecular biology of oat (Avena spp.) in recent years. Many of these were recently described at the Fourth International Oat Conference, held on 18 to 23 October, in Adelaide, South Australia. These advances include a report of oat transformation and regeneration, the characterisation of J3-glucanase genes in oat, the further development of a molecular genetic map in oats, and the characterisation of genes encoding novel oat grain proteins. A technique for assessing pedigrees in the oat and other cereal crops has been reported using a modified electrophoretic technique.
Abstract— Storage roots are important for the growth and development in plants because they provide nutrients, water, and energy storage. Storage roots are also modulating growth direction, disease resistance, and root formation at the cellular and molecular level through interactions of genes and gene networks. However, molecular mechanisms regulating storage root formation in plants are not fully understood. In this review, we have overviewed transcriptional regulation of storage root formation, proteomic regulation of storage root formation, ethylene regulation of storage root formation, auxin regulation of storage root formation, gene expression regulation of storage root formation, and metabolism regulation of storage root formation. We have reviewed the basic regulatory principles of storage root formation from the network of genomics to proteomics and metabolism in plants that will be valuable to research work in storage root growth and development regulation at the molecular level.
Research on Trivedi Effect -Impact of Biofield Treatment on Growth and Yield ...john henrry
Research done by Mahendra Trivedi - This study tested the impact of Trivedi Effect applied to lettuce and tomato seeds and transplants in commercial plantings with and without fertilizers and pesticides, in relation to yield, quality, and pest inhibition.to read research visit http://www.academicroom.com/article/impact-biofield-treatment-growth-and-yield-lettuce-and-tomato
Research on Trivedi Effect -Impact of Biofield Treatment on Growth and Yield ...Abby Keif
Research done by Mahendra Trivedi - This study tested the impact of Trivedi Effect applied to lettuce and tomato seeds and transplants in commercial plantings with and without fertilizers and pesticides, in relation to yield, quality, and pest inhibition. Read Complete research at: http://works.bepress.com/mahendra_trivedi/1/
Antioxidant activity, photosynthetic rate, and Spectral mass in bean Plants (...IJEABJ
An increase in antioxidant activity is a common response in plants as a defense mechanism against biotic and abiotic stress factors, such response is also generated with the exogenous application of "defense activators", which have negative effects on plant metabolism. In this work, bean plants (Phaseolus vulgaris L.) cv. Pinto Nacional were treated with jasmonic acid (0.5 mM), salicylic acid (2 mM), Trichoderma asperellum (105 spores/ml), and Bacillus pumilus (105 CFU / mL), in order to determine the level of structural and metabolic response of the plants. On the seventh day after the application of the treatments, it was measured the enzymatic activity of catalase (CAT), peroxidase (POX), and superoxide dismutase (SOD). In addition, leaf impressions were taken to measure the stomatal opening and conductance, photosynthetic rate, and the mass spectrum (mass/charge, m/z). The antioxidant activity increased in plants treated with jasmonic acid and T. asperellum, which in turn significantly increased the stomatal opening and conductance, and photosynthetic rate. The mass profile showed that the plants treated with T. asperellum have a greater quantity of masses/charge, of which some had statistically highly significant difference according to the means test Tukey (p <0.05). It is concluded that some defense activators such as jasmonic acid and T. asperellum increase the antioxidant activity, defense response that concurs with the high photosynthetic and metabolic rate in bean plants.
Genetic variability and phylogenetic relationships studies of Aegilops L. usi...Innspub Net
Studying of genetic relationships among Aegilops L. species is very important for broadening the cultivated wheat genepool, and monitoring genetic erosion, because the genus Aegilops includes the wild relatives of cultivated wheat which contain numerous unique alleles that are absent in modern wheat cultivars and it can contribute to broaden the genetic base of wheat and improve yield, quality and resistance to biotic and abiotic stresses of wheat. The use of molecular markers, revealing polymorphism at the DNA level, has been playing an increasing part in plant biotechnology and their genetics studies. There are different types of markers, morphological, biochemical and DNA based molecular markers. These DNA-based markers based on PCR (RAPD, AFLP, SSR, ISSR, IRAP), amongst others, the microsatellite DNA marker has been the most widely used, due to its easy use by simple PCR, followed by a denaturing gel electrophoresis for allele size determination, and to the high degree of information provided by its large number of alleles per locus. Day by day development of such new and specific types of markers makes their importance in understanding the genomic variability and the diversity between the same as well as different species of the plants. In this review, we will discuss about genetic variability and phylogenetic relationships studies of Aegilops L. using some molecular markers, with theirs Advantages, and disadvantages.
Presentation from the International Life Sciences Institute, India - "Scientific Workshop on Safety Assessment of GM Foods" held on 14-15 October, 2015 in New Delhi, India
Breeding for Development of Climate Resilient Chickpea.pptxKanshouwaModunshim
The breeding for the development of Climate Resilient Chickpea is a critical initiative aimed at enhancing the productivity and adaptability of chickpea genotypes under challenging environmental conditions. Chickpea, a vital pulse crop globally, faces yield limitations due to the combined impact of heat, cold, drought, and salinity stresses. The average yields, currently far below the potential, necessitate the development of highly productive and resilient chickpea cultivars. Traditional breeding methods and modern genomic resources, including molecular markers, genetic maps, and QTL identification, have been instrumental in enhancing grain yields and stress adaptation. Marker-assisted backcrossing has successfully produced cultivars like Pusa Manav, demonstrating the effectiveness of genomic technologies. Additionally, the adoption of gene-editing technologies, such as CRISPR-Cas9, holds promise in accelerating genetic gain for stress-related traits.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
Salas, V. (2024) "John of St. Thomas (Poinsot) on the Science of Sacred Theol...Studia Poinsotiana
I Introduction
II Subalternation and Theology
III Theology and Dogmatic Declarations
IV The Mixed Principles of Theology
V Virtual Revelation: The Unity of Theology
VI Theology as a Natural Science
VII Theology’s Certitude
VIII Conclusion
Notes
Bibliography
All the contents are fully attributable to the author, Doctor Victor Salas. Should you wish to get this text republished, get in touch with the author or the editorial committee of the Studia Poinsotiana. Insofar as possible, we will be happy to broker your contact.
3. Introduction
The first completed plant genome sequence, that of Arabidopsis thaliana, was
published in the year 2000. Genome mapping and sequencing projects are on
going in a number of other plant species, including many commercially
important crops.
These projects are complemented by the availability of increasing numbers of
plant ESTs, currently over 250 000, representing a wide variety of species.
For the first time, therefore, it is possible to begin to look at all aspects of plant
biology on a global scale. This includes aspects that are of particular interest in
agriculture, such as growth and development, tolerance or resistance to stress
and disease, and metabolic activity.
4. Traditionally, there have been two approaches to improving the quality of
cultivated plants. The first is by conventional breeding, which involves
exploiting varietal or specific differences and using crosses and tissue-
culture-based techniques to concentrate favourable traits in particular
plant lines.
One problem with this approach is that many of the most valued traits in
agriculture – disease resistance, stress resistance, increased yield etc. – are
controlled by QTLs, so complex and extensive breeding programmes are
reguired.
5. The alternative is genetic engineering, because single genes from other
species can often confer desirable traits on plants. Although this approach
to agricultural improvement is comparatively rapid, the behaviour of the
transgenes is unpredictable and there is much public concern about the
long-term effects of such plants on and the environment.
Genomic resources now provide an additional route to the improvement
of plants, through the rapid identification of genes and pathways
controlling important plant traits.
The technology and application of genetic engineering in plants is
discussed in detail in our sister text, Principles of Gene Manipulation.
Some of the issues of public concern over the use of transgenic plants and
food products derived therefrom have been discussed.
6. Global Gene Expression Profiling
Gene expression profiling is the determination of the pattern of genes
expressed, at the level of transcription, under specific circumstances or in a
specific cell to give a global picture of cellular function.
Initial studies of global gene expression in plants were small in scale. The
random sampling of EST sequences from rice suspension cells and
Arabidopsis plants exposed to osmotic stress helped to reveal a number of
stress-induced genes . The first array-based study involved a glass
microarray containing 48 Arabidopsis ESTs and compared gene expression
in two tissues – roots and leaves.
7. A similar study with a larger number of ESTs was performed by Ruan et al.
(1998) and, in the same year, Arabidopsis microarrays containing about
800 ESTs were used to study light-induced gene expression. Interestingly,
the first plant microarray experiment with direct agricultural implications
involved not Arabidopsis but strawberry, where 200 genes were shown to
undergo changes in expression during ripening.
Over the last 2 years, an increasing number of expression profiling
experiments have been carried out to investigate gene expression changes
associated with traits of agricultural value.
8. EST sampling projects in two naturally salt-tolerant species
(Mesembryanthemum crystallinum and Dunaliella salina) and two species
resistant to desiccation (Tortula ruralis and Craterostigmata plantagineum)
have been used to identify drought stress-related genes. Sampling
differences between well-watered and salt-stressed or desiccated plants
were used to identify ESTs either induced or repressed by these extreme
conditions.
Large-scale microarray-based screening projects have been undertaken to
identify drought stress-related genes in Arabidopsis, rice and M.
crystallinum and oxidative stress-related genes in Arabidopsis.
9. They found that over 700 transcripts showed significantly increased or
reduced expression levels, some of which were specific to particular
treatments (e.g. exposure to chemicals such as methyl jasmonate and
salicylic acid which are known defence-related signalling molecules) and
some of which were general (i.e. affected by multiple treatments).
These data suggested that there was considerable cross-talk between
different defence signalling pathways.
Microarrays have also been used to study the response of the plant to biotic
stresses. Schenk et al. (2000) have recently investigated disease defence
responses in Arabidopsis thaliana using microarrays containing about 2400
cDNAs.
10. Reymond et al. (2000) studied the effect of mechanical wounding and
insect feeding on gene expression profile in Arabidopsis.
The phenomenon of cross-talk may represent a problem when devising
strategies to combat disease, because artificially modifying the response
to one stimulus could alter the response to several others in an
undesirable way.
However, as well as identifying common themes in transcriptional profiles,
microarray analysis can also separate individual responses.
11. Thus, strategies to counteract the effects of insect feeding could be
targeted to a specific subset of genes so as not to interfere with water
stress tolerance. As well as local defence responses, the transcriptional
changes accompanying systemic acquired resistance have also been
monitored at the global level in Arabidopsis.
They found that mechanical wounding induced a number of genes also
known to be involved in the response to water stress, while such genes
were only minimally affected by insect feeding.
12. Proteomics and Plant Breeding
Two-dimensional gel electrophoresis (2DE) is a technique for the high-
resolution separation of proteins, allowing systematic protein
characterization and the identification of proteins that are differentially
expressed in alternative sample.
The technique has also been used to characterize proteins that are
involved in stress response pathways, e.g. the response to drought, cold
and heat shock.
14. 2DE has also been used as a diagnostic tool in plant breeding because
different lines or cultivars often show polymorphisms in terms of the
spots generated on two-dimensional gels. Such differences have allowed
unambiguous genotyping in many plant species, including rice, wheat and
barley .
Polymorphism occurs at three levels. Firstly position shifts (PS), which often
correspond to mutations that change the mass and/or charge of the protein.
Similarly, 2DE has been used to distinguish between intraspecific variants
and to investigate the taxonomy of closely related species, e.g. in the genus
Triticum.
15. The first two types of polymorphism are generally Mendelian characters
and represent useful genetic markers. These have been used in wheat,
maize and pine, for example, to generate comprehensive genetic maps also
containing DNA markers such as RFLPs, RAPDs and AFLPs.
Quantitative polymorphisms are useful for identifying QTLs that cannot be
pinned down by traditional map-based cloning or functional candidate
approaches . The basis of this method is that PQLs that map co incidentally
with QTLs can be used to validate candidate genes.
Secondly presence/absence polymorphisms (P/A), where a protein is present
in one sample but absent in another. Finally quantitative variants,
corresponding to so-called protein quantity loci (PQLs).
16. An example is provided by the study of de Vienne et al. (1999) who
identified a candidate gene on chromosome 10 of maize for a QTL
affecting drought response. The candidate gene was ASR1, known to be
induced by water stress and ripening.
Verification of the association was made possible because a PQL found by
the comparison of 2DE gels from control and drought stressed maize
plants mapped to the same region; the PQL controlled levels of the ASR1
protein under different drought stress conditions.