PLANT PATHOGEN INTERACTION

POOJA DOGRA

ROLL. NO - 1468

M.Sc. Agriculture Biotech.

Date – 07-01- 2015

Objective

• Introduction• Pathogen• Plant defence• Elictors• Induced defence• Systemic defence• Pathogen related protein• secondary compounds• Communal resistance

INTRODUCTION

The contact between plant and pathogenic microorganism lead to a particular chain of events in the plant organism.

Communication requires a mobile ‘systemic signal’.

Interaction lead to two type of response:

compatible response

incompatible response

Brian C. Freeman and Gwyn A. Beattie. 2008

Pathogen

An agent that causes infection or disease,

especially microorganism, such

as a bacterium or protozoan,or a virus.

Necrotrophic pathogen ex - gray mold fungus Botrytis cinerea

bacterial pathogen Erwinia carotovora

Biotrophic pathogen

PLANT PATHOGEN fungus Blumeria graminis

bacterial pathogen Xanthomonas oryzae

Hemibiotrophic pathogen

fungus Magnaporthe grisea

Brian C. Freeman and Gwyn A. Beattie. 2008

Examples

• Late Blight of PotatoCaused by the fungus Phytophthora

infestans

• Ergot of Rye Caused by the fungus Clavicepspurpurea

• The pathogen produces a structure called a sclerotium that

grows in place of the rye kernel.

Plant defense

constitutive• Cell walls• Waxy epidermal cuticle• Bark• Thorns, Spine

Inducible• Toxic chemicals• Pathogen degrading enzymes• Deliberate cell suicide• Systemic resistance

Elicitors of defense responses

• Any substance that has the capability of activating defense responses in plants

• Include components of the cell surface as well as excreted metabolites

Elicitors

General Race specific

a) Oligosaccharide elicitors a)avr gene products

b) Protein/peptide elicitors

(Meenakshi Thakur and Baldev Singh Sohal 2012)

(Teiz and ziger)

Induced defence

Induced defence

Programmed cell death

(PCD)

Induced structural barriers

phytoalexins

Pathogenesis related

proteins (PR-proteins)

Post transcriptional gene

silencing (PTGS)

Heil, M., and R.M. Bostock. 2002

Hypersensitive response

HRlesions Rapid, localized plant cell death upon contact with

avirulent pathogens. HR is considered to be a key

component of multifaceted plant defense

responses to restrict attempted infection by

avirulent pathogens.

Host cell recognizes the bacterium and initiates

programmed cell death to restrict the growth of the

pathogen, which thus does not cause disease.

HR also contributes to the establishment of the

long-lasting systemic acquired resistance against

subsequent attack by a broad range of normally

virulent pathogens.

• HR Includes:

– oxidative bust (production of reactive oxygen species)

– Disruption of cell membranes

– opening of ion channels

– Cross linking of phenolics with cell wall component

– Production of anti-microbial phytoalexins and PR protein

– apoptosis (programmed cell death)

Systemic Acquired Resistance (SAR)

SAR is a mechanism of induced defense that confers long-lasting protection against a broad spectrum of microorganisms.

Enhance resistance against subsequent attack by a wide array of pathogen.

The vasculature provide the excellent channel for transport of systemic signals.

SAR induces the chromatin modification.

• Pathogen recognition triggers a number of rapid cellular responses, including ionic changes, and phosphorylationcascades, which precede the accumulation of reactive oxygen species, nitric oxide, and salicylic acid (SA) and the transcriptional activation of defence-related genes.

• SA also has a key role in establishing local and systemic resistance to many virulent biotrophic pathogens.

Systemic signals in plant defence These mobile signals help in

activation of SAR.

Mostly metabolites function as systemic signal, contributing to long distance signaling in plant defence.

Pathogenesis-Related Proteins(PR-proteins)

• Pathogenesis related proteins, called PR-proteins- A group of plant coded proteins

• Are structurally diverse group toxic to invading pathogens.

• Produced under stress

• They are widely distributed in plants in

trace amounts but are produced in high

concentration following pathogen attack

Significance of PR-proteins

• They show strong antifungal and other antimicrobial activity.

• These are associated with strengthening of the host cell wall and its out growths and papillae.

• Some of the PR-proteins, for example, B-1, 3-glucanase and chitinase, diffuse towards and affect (break down) the chitin-supported structure of the cell walls of several plant pathogenic fungi, whereas lysozymes degrade the glucosmine and muramic acid components of bacterial cell walls.

Secondary Compounds

• Secondary metabolites are not directly involved in growth or reproduction but they are often involved with plant defense. These compounds usually belong to one of three large chemical classes: terpenoids, phenolics, and alkaloids.

• Secondary compounds have negative impacts on herbivores and pathogens

• Tannins are water-soluble flavonoid polymers produced by plants and stored in vacuoles. Tannins are toxic to insects because they bind to salivary proteins and digestive enzymes including trypsin and chymotrypsin resulting in protein inactivation.

• lignin provides an excellent physical barrier against pathogen attack.

• Furanocoumarins are phenolic compounds produced by a wide variety of plants in response to pathogen.

Communal resistance

Plant can communicate with their neighboring plantthrough the production of

volatile singles- Methyle jasmonate

Methyle salicylate

there by activation of defense gene in neighboring plant.

Ex: Methyle jasmonate from Big sagebrush (Artemisia tridentate) induce production of protease inhibitor in adjacent tomato plant.

(Stout & Duffey, 1996)

Conclusion

• As plant being sessile in plant suffers from various abiotic and biotic insults. In which biotic stress is produce through the living organisms. Plants have several strategy to surpass these conditions. They make their defense strategy by first line of defense e.g. Cell walls Waxy epidermal cuticle, Thorns, Spine. and second line of defense by producing chemical toxins, secondary metabolite, and by SAR,PR.

• To produce biotic stress tolerance crop researcher are mainly focusing on PR proteins. By understanding the mechanism of PR we can produce high yielding crop varities.

References

• Brian C. Freeman and Gwyn A. Beattie. 2008. An Overview of Plant

Defenses against Pathogens and Herbivores

• Heil, M., and R.M. Bostock. 2002. Induced systemic resistance (ISR) against pathogens in the context of induced plant defenses.

• Role of Elicitors in Inducing Resistance in Plants against Pathogen Infection: A Review Meenakshi Thakur and Baldev Singh Sohal 2012

• Teiz and ziger

• Biotechnology – u.satyanaryna

Thank you