Presenter: Mahboob ullah Lab: Organic and natural products chemistry.

Key words (1) Plant microbe interaction (2) Defence responses of plant (3) Molecular arms race b/w plants and pathogen (4) Strategies for disease resistance breeings (5) Summary

Plant microbe interaction  Plants secrete various organic compounds resulting in a nutritionally enriched environment favorable for microbial growth;  As a result, plants are heavily colonized with a diversity of microorganisms whose reservoir is primarily the soil. Generally  Microbes that colonize plants are called either epiphytes (colonize plant surface) or endophytes (colonize plant interior)

DEFENCE RESPONSES OF PLANT Methyl salicylate

Compatible interaction  disease Incompatible interaction  resistance TWO TYPES OF INTERACTION 3 aspects of response from plant side 1. Hypersensitive 2. Local 3.Systemic

Incompatible interaction Two layered PAMPs PTI ETI INCOMPATIBLE INTERACTION  PTI plays a key role at the pre invasion stage to stop potential pathogen from host cell  ETI triggered at the post invasion stage to prevent growth and proliferation of pathogen. Programmed cell death.

The molecular arms race between plants and pathogens  2006 Jones and Dangle zigzag model four phases of plant microbe co evolutionary concept. Zig zag model of plant pathogen interaction  Two American biologist  According to this the plant and pathogen are both evolving for survival.  PAMPs from pathogen and PRR(PTI) from plant.

PLANT PATHOGEN INTERACTION AND DEVELOPMENT OF DISEASE RESISTANCE. Guard proteins

Plant diseases and their biological control Pseudomonas syringae Pseudomonas syringae is a rod-shaped, Gram-negative bacterium with polar flagella. As a plant pathogen, it can infect a wide range of species The incompatible interaction is extensively exploited by plants breeders to raise resistance cultivars for crop production in modern agriculture

 Two bacterial proteins can bind to the plant protein RIN4, tag it with phosphate groups (circled 'P') a, In susceptible plants, this downgrading of plant defences results in the spread of the bacterium. b, Resistant plants make use of the RPM1 protein to sense these manipulations of RIN4 by the bacterial Avr proteins, activating the hypersensitive response which prevents bacterial spread. (P. syringae infects A. thaliana leaves.)  Arabidopsis thaliana resistance (R) protein RPM1, and the Pseudomonas syringae avirulence (Avr) proteins AvrRpm1 and AvrB

A: Non- host resistance: bacteria enter the plant and recognition of a PAMP by the corresponding PRR B : A possible mechanism for overcoming non-host resistance in plants is the evolution of non-eliciting PAMPs, which are not recognised by the specific plant PRR. C:The evolution of effector proteins (E) in pathogens is an alternative strategy for overcoming non-host resistance D : The evolution of effectors in pathogens consequently led to the evolution of cultivar-specific resistance in plants. To overcome the suppression by effectors, certain cultivars of a susceptible plant species evolved R proteins that recognise the activity of the corresponding effector molecule EVOLUTION OF DISEASE RESISTANCE

SUMMARY  Plant disease has a major threat for crop production,modern agriculture and food security.  Application of pesticides can be a cost for environment and human health.  Utilization of resistant cultivars is th e most effective approach to disease control.

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