effector proteins in disease development and resistance

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Name: Koli Ganapati ID.No.: MA1TAE0134Sr. Msc (Agri)

ROLE OF PATHOGEN DERIVED ROLE OF PATHOGEN DERIVED EFFECTOR PROTEINS IN PLANT EFFECTOR PROTEINS IN PLANT

DISEASE AND RESISTANCE DISEASE AND RESISTANCE

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1) Introduction

2) Mechanism of Effectors

3) Evolutionary process

4) Case studies

5) Conclusion

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Effectors - Pathogen proteins, small molecules that alter host-cell structure and function.

Dual role of effector protein 1)Disease development 2) Defense system

(Hogenhout et al., 2008)

INTRODUCTION

Effectors

Effector- host Immunity

Ability to trigger the hypersensitive response in resistant plants (avirulence activity) then suppress defence

Virulence in susceptible plants (typically host plants that lack effective resistance[R] genes)

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(Block et al.,2008)

Mechanism of Effectors

6 (Hogenhout et al., 2008)

1. Delivery of effectors into host cells

2. Action of effectors in the apoplast

3. Suppression of Plant immunity

4. Some effectors alter plant behavior and

development

5. Molecular mimicry by effectors

1. Delivery of effectors into host cells

Plant deliver effector proteins inside host cells through a diversity of mechanism

Virus

Bacteria -T3SS (Block et al., 2008)

Fungi – haustoria (Whisson et al., 2007)

Plant parasitic nematodes –the stylet to inject their effector proteins inside a parasitized plant vascular cell

(Davis et al, 2008)

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Fungi

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Bacteria -T3SS

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(Block et al., 2008)

Virus

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Nematodes –Stylet

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Resistance and disease pathway

12(Goel et al.,2007)

2. Action of effectors in the apoplast

Act at the plant-microbe interface, where they interfere with apoplastic plant defenses (Van der Hoorn, 2008)

Examples 1) Effectors of Cladosporium fulvum. - Parasite of tomato - Avr2, Avr9, Avr4, and ECP2 - function exclusively in the apoplast (Thomma et al., 2005)

2) Oomycetes - Phytophthora infestans - secrete apoplastic effectors (Tian et al., 2007)

Inhibit and protect pathogen against plant hydrolytic enzyme. 13

1) Contributes to virulence by suppressing basal defenses 2) Suppress hypersensitive cell death elicited by various Avr proteins Examples Oomycete - RXLR effectors suppress host immunity

P. infestans -Avr3a suppresses the hypersensitive cell death

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3. Suppression of Plant immunity

4. Effectors Alter Plant Behavior and Development

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Coronatine

5. Molecular mimicry by effectors

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4) Evolutionary Process

Four-part model for Plant disease and resistance “ Central Dogma of Plant Pathology”

A) PAMP recognition triggers immunity -ResistanceB) Effectors suppress immunity - SusceptibilityC) R proteins recognize effector activities-ResistanceD) Effector recognized by R protein is lost or modified

-Susceptibility

17 ( Bent and Mackey 2007)

“Central Dogma” of Plant Pathology

(Bent and Mackey, 2007)

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Plant resistant gene

19(Hammond-Kosack and Kanyuka, 2007)

Functions of effector proteins from Plant pathogenic bacteria

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Functions of effector protein from plant pathogenic fungi

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Contd.,

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Objective: Role of for CRN effectors in the suppression of host defense responses.

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(Tingli Liu et al.,2011)

Identification of a group of P. sojae-specific effectors.

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Relative expression of PsCRN63, PsCRN77, PsCRN84, PsCRN86, and

PsCRN115 in vegetative hyphae. Expression levels relative to PsCRN63.

Expression analysis of the group of CRN effectors in P. sojae.

(Tingli Liu et al.,2011)

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Functional analysis of PsCRN63 and PsCRN115

A PsCRN63 triggers cell death in N. benthamiana. PsojNIP (positive

control), PsCRN63, PsCRN115, or gfp (negative control). Photographs

were taken 5 d after infiltration. (Tingli Liu et al.,2011)27

Generation of transformants with silenced PsCRN63 and PsCRN115 genes. Relative expression of PsCRN63 and PsCRN115 in silenced lines T3, T20, and T21 and the wild type (WT) is shown.

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Objective: To know the role of how plants succesfully elicit

HR based PCD in response to effectors activity.

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30(Robert et al, 2005)

AvrPtoB induced disease susceptibility in RGpto11 tomato leaves

Objective: To find a novel model for the involvement of host

factors in effectors recognition.

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Objective : The role of Mi-CRT in the plant– nematode interaction and

showed that the knock-down of MiCRT gene expression in nematodes decreased the ability of these parasites to infect plants.

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Effect of calreticulin (CRT) Mi-CRT knockdown on Meloidogyne incognita virulence.

(Jaouannet et al., 2012) 34

Effect of the overproduction of calreticulin (CRT) Mi-CRT on Arabidopsis thaliana susceptibility to Meloidogyne incognita.

(Jaouannet et al., 2012) 35

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