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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) Interaction

3) Mechanism of Effectors

4) Evolutionary process

5) Case studies

6) Conclusion

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FLOW OF SEMINAR

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Effectors - Pathogen proteins, small molecules that alter host-cell structure and function.Dual role of effector protein

- Infection (virulence factors and toxins)

- defense

(Hogenhout et al., 2008)

INTRODUCTION

• PATHOGEN DERIVED EFFECTORE PROTIENS

• FUNGI

• BACTERIA

• VIRUS

• NEMATODE

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Effectors concept

Effector” - plant-microbe interactions

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

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

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(Block et al.,2008)

Mechanism of Effectors

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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

Pathogens

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

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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Bacteria -T3SS

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Fungi – haustoria

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Nematodes –Stylet

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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. 12

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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The Pseudomonas syringae phytotoxin coronatine mimics jasmonoyl-isoleucine (JA-Ile), which is a crucial plant signaling molecule for regulating plant defense responses.

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

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“Central Dogma” of Plant Pathology

(Bent and Mackey, 2007)

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Plant resistant gene

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Contd.,

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Functions of effectors protein 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 : 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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A: Expression levels of the Mi-CRT gene in the nematodes feeding on plants overproducing hpMi-CRT. B, Mean number of galls produced on infected wildtype (Wt) and hpMi-CRT plants.C, Mean number of egg masses per gall.Two independent biological replicates were carriedout, with 24 plants per condition

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

(Jaouannet et al., 2012) 25

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

(Jaouannet et al., 2012)

A and B, Mean number of galls produced by M. incognita on infected wild type (Wt) and Mi-CRT+SP (A) or Mi-CRT-SP (B) overexpression lines of A. thaliana. C, and D, Mean number of egg masses per gall SEM. Kruskal-Wallis tests were carried out for statistical analysis.

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Effect of the overproduction of calreticulin (CRT) Mi-CRT on Arabidopsis thaliana susceptibility to Phytophthora parasitica. Disease progression on A. thaliana plants overproducing A, Mi-CRT+SP or B, Mi-CRT-SP Inoculated with P. parasitica, as assessed by disease index (Attard et al. 2010).

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

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Phylogenetic relationships of a group of CRN effectors in three Phytophthora species. Putative pseudogenes are indicated with asterisks, and the two functional analyzed genes are denoted by boxes. CRN genes, designated Ps, Pi, and Pr, correspond to P. sojae, P. infestans, and P. ramorum, respectively.

(Tingli Liu et al.,2011)

Identification of a group of P. sojae-specific effectors containing FLAK motifs and NLS.

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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)31

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)32

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. The expression of PsCRN63 in the wild type was set as 100%.

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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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A model for AvrPtoB induced disease susceptibility in RGpto11

tomato leaves. RG-pto11 plants lack a functional Pto protein and

are susceptible to DC3000 infection. 36

(Robert et al, 2005)

A model for AvrPtoB induced disease susceptibility in RGpto11 tomato leaves

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

factors in effectors recognition.

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(Jeffrey et al., 2008)

(A) In uninfected plants, NRIP1 localizes to the stroma of chloroplasts and N localizes to the cytoplasm and nucleus (data not shown).(B) When TMV infects the plant, NRIP1 is first retained in or recruited to the cytoplasm by TMV’s p50 domain via protein-protein interactions.(C) NRIP1 mediates the association of p50 and N’s TIR domain to form an active immune complex in the cytoplasm. This complex may contain unknown (?) host components required for the activation that are only recruited by a NRIP1-p50 complex. Activated cytoplasmic N either enters the nucleus or sends a signal to nuclear-localized N to initiate a defense response.

Model of Recognition by an N-NRIP1-p50 Complexhealthy infected (p50) infected (p50)

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(-SP)NRIP1-Cerulean coinfiltrated with p50-TAP (top right) induces HR cell death in N containing N. benthamiana plants. (-SP)NRIP1-Cerulean coinfiltrated with TAP alone (top left) does not induce cell death. HR occurs normally when Cerulean alone is coinfiltrated with p50-TAP (bottom right). Coinfiltration of Cerulean alone and TAP alone does not induce HR (bottom left). The black outlines mark the site of infiltration.

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