The document summarizes different types of plant defense mechanisms against pathogens, including passive defenses like waxy cuticles and cell wall appositions, as well as active defenses like phytoalexins, PR proteins, protein synthesis inhibitors, and tannins and melanins. It describes several examples of these defenses such as phytoalexins including isoflavonoids and stilbenes, and the roles of PR proteins like β-1,3-glucanases and chitinases in weakening fungal cell walls. The document concludes that understanding these defense mechanisms provides insights into plant adaptation and development, while further study of their gene regulation could aid crop improvement.
plant pathogen interaction
different types of pathogens
gene for gene hypothesis
direct receptor model
Elicitor receptor model
suppersor repressor model
gaurd hypothesis
plant pathogen interaction
different types of pathogens
gene for gene hypothesis
direct receptor model
Elicitor receptor model
suppersor repressor model
gaurd hypothesis
This ppt illustrates and describes the two bacterial diseases included in the BSc Hons Program Syllabys Core Course III or DSC 3- Citrus canker and angular leaf spot of cotton
It is a biofertilizer that contains symbiotic Rhizobium bacteria which is the most important nitrogen-fixing organism. These organisms have the ability to drive atmospheric Nitrogen and provide it to plants. It is recommended for crops such as Groundnut, Soybean, Red-gram, Green-gram, Black-gram, Lentil, Cowpea, Bengal-gram and Fodder legumes, etc.
This ppt illustrates and describes the two bacterial diseases included in the BSc Hons Program Syllabys Core Course III or DSC 3- Citrus canker and angular leaf spot of cotton
It is a biofertilizer that contains symbiotic Rhizobium bacteria which is the most important nitrogen-fixing organism. These organisms have the ability to drive atmospheric Nitrogen and provide it to plants. It is recommended for crops such as Groundnut, Soybean, Red-gram, Green-gram, Black-gram, Lentil, Cowpea, Bengal-gram and Fodder legumes, etc.
"Bio - Warfare During Host Pathogen Interactions in Indigenous Crop Plants" b...Md. Kamaruzzaman
This is a analysis of some collected information of the subject of my M.S. theory semester. Course title was Plant Pathogenesis and Genetics of Plant Pathogens
Pathogenesis-related proteins (initially named “b” proteins) were discovered in tobacco leaves
hypersensitively reacting to TMV by two independently working groups (Van Loon and Van Kammen,
1970; Gianinazzi et al., 1970)
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.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
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.
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.
Biochemical basis for resistance to plant pathogens
1. Department of Entomology and Agricultural Zoology
Institute of Agricultural Sciences
Banaras Hindu University
Presented by:
Mamoon Rasheed
M.Sc. (Ag.) Prev
Department of Mycology and Plant Pathology
2. • Disease resistance is the ability of a plant to prevent, restrict, or
retard disease development, and occurs at high, moderate, or
low levels.
• Capabilities of plants to dissuade the adversaries depend a
great deal on the preformed structures and pathogen induced
responses.
• These are
• Passive Defence
• Active Defence
Introduction
Source : Santaram, Akundi. (2000). Biochemical and Molecular Aspects of Disease Resistance in Plants. Geobios.
27. 205-216.
3. • The Cuticle : Cutin and waxes together comprise the cuticle
• Carbohydrate Appositions : the resistant host responds by
synthesizing new carbohydrates, particularly callose and cellulose
• Gels and Tyloses : Vascular gels coat the walls and fill the infected
vessels in numerous plant species infected with fungi
• Structural Proteins : b-proteins of tobacco
Passive Defense
4. • Phytoalexins
• Protein synthesis inhibitors
• PR Proteins
• Tannins and melanins
Active Defense
5. • Ribosome inactivating proteins found in the seed extracts
are known to prevent protein synthesis
• They act on the large ribosomal subunit to inactivate the
ribosome to carry out the polypeptide chain elongation
Protein synthesis inhibitors
Source : Jimenez, A., and D. Vazquez. "Plant and fungal protein and glycoprotein toxins inhibiting
eukaryote protein synthesis." Annual review of microbiology 39.1 (1985): 649-672.
6. • These antibiotics, produced after infection, include a variety of natural
compounds:
• Isoflavonoids, Flavonoids
• Dihydrophenanthrenes
• Stilbenes
• coumarins, isocoumarins
• Terpenoids
• furanoacetylenes, polyacetylenes, and polyenes.
Phytoalexins
Source : Ingham, J. L., Harhorne, J. B. 1976. Phytoalexin induction as a new dynamic approach to the study of
systematic relationships among higher plants. Nature 260:241-43
7. Phytoalexins
Source : Ingham, J. L., Harhorne, J. B. 1976. Phytoalexin induction as a new dynamic approach to the study of
systematic relationships among higher plants. Nature 260:241-43
8. • Necrosis associated with race-specific resistance normally is characterized by the
formation of brown to black pigments (melanin) throughout the cell walls and the
collapsed protoplasts.
• Melanins in plants are formed principally from various ortho-dihydroxyphenolic
compounds
• The enzymes polyphenoloxidase (PPO) and peroxidase (PO) oxidize the colorless
dihydroxyphenols to give the colored ortho-quinones
Production of tannins and melanins
Source : Mayer, A. M., Harel, E. 1979. Review: polyphenol oxidases in plants. Phytochemistry 18:193-215
9. • Proteins encoded by the host plant but induced only in
pathological or related situations, the latter implying situations of
non-pathogenic origin
• PR 2 : Shows β-1,3-glucanase activity
• PR 3 :Shows Chitinase activity
• PR 12 : Plant defensins
PR Proteins
Source : Edreva, A. (2005). Pathogenesis-related proteins: research progress in the last 15 years. Gen Appl Plant
Physiol, 31(1-2), 105-24.
10. PR2 Mode of action
β-1,3-glucanases are involves in hydrolytic cleavage of the 1,3-β-D-glucosidic linkages in β- 1,3-
glucans, a major componant of fungi cell wall. So that cell lysis and cell death occur as a result
of hydrolysis of glucans present in the cell wall of fungi.
11. • Cleaves the cell wall chitin polymers , resulting in a weakened cell wall and
rendering fungal cells osmotically sensitive
• These Chitinases have Significant antifungal activities against plant
pathogenic fungi like
• Alternaria sp.
• Bipolaris oryzae for brown spot of rice
PR3 Mode of action
Source : Nejad, M. S., Bonjar, G. H. S., & Dehkaei, F. P. (2014). Control of Bipolaris oryzae the causal agent of rice
brown spot disease via soil Streptomyces sp. isolate G. International Journal of Advanced Biological and Biomedical
Research, New Delhi, 2, 310-317.
12. PR12 Mode of action
Source https://www.macmillanhighered.com/BrainHoney/Resource/6716/digital_first_content/trunk/test/hillis2e/hillis2e_ch28_2.html
13. Conclusion
• These play important role in disease resistance and also help the plant to adapt to the
environmental stress.
• The increasing knowledge about the these gives better idea regarding the development
and defense system of plants.
• Primary aspects of the gene regulation of the biochemical factors are understood but the
study of exact mechanism of gene regulation and receptor cascade will open new ways
for the plant genetic engineering technology for crop improvement.
