Type I J-Domain NbMIP1 Proteins Are Required for Both Tobacco Mosaic Virus Infection and Plant Innate Immunity

Yumei Du,Yule Liu,Haili Zhang,Ling Zhang,Jinping Zhao,Yiguo Hong,Fangming Xiao,Qi Liu,Tianyuan Chen,Yan Wang,Qianhua Shen,Savithramma P Dinesh-Kumar

doi:10.1371/journal.ppat.1003659

Abstract

Tm-22 is a coiled coil-nucleotide binding-leucine rich repeat resistance protein that confers durable extreme resistance against Tomato mosaic virus (ToMV) and Tobacco mosaic virus (TMV) by recognizing the viral movement protein (MP). Here we report that the Nicotiana benthamiana J-domain MIP1 proteins (NbMIP1s) associate with tobamovirus MP, Tm-22 and SGT1. Silencing of NbMIP1s reduced TMV movement and compromised Tm-22-mediated resistance against TMV and ToMV. Furthermore, silencing of NbMIP1s reduced the steady-state protein levels of ToMV MP and Tm-22. Moreover, NbMIP1s are required for plant resistance induced by other R genes and the nonhost pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. In addition, we found that SGT1 associates with Tm-22 and is required for Tm-22-mediated resistance against TMV. These results suggest that NbMIP1s function as co-chaperones during virus infection and plant immunity.

Highlights

Plants have evolved an effective immune system against pathogen attack
We found that in Nicotiana benthamiana, Tm-22-mediated resistance against Tobacco mosaic virus (TMV) and Tomato mosaic virus (ToMV) requires MIP1s (NbMIP1s), a group of J-domain proteins that may act as molecular chaperones to assist protein folding and maintain protein structure
Nicotiana benthamiana J-domain MIP1 proteins (NbMIP1s) are required for resistance mediated by other resistance proteins and resistance to the bacterial nonhost pathogen Pseudomonas syringae pv. tomato (Pst) DC3000

Summary

Introduction

Plants have evolved an effective immune system against pathogen attack. One of the most efficient plant defenses is mediated by resistance (R) genes [1]. The R gene product directly or indirectly recognizes the corresponding pathogen avirulence (Avr) protein and activates strong, specific responses that limit pathogen growth. R-mediated resistance is often accomplished by rapid local programmed cell death (PCD), known as the hypersensitive response (HR). There are exceptions where no PCD is triggered [2,3]. Rx from potato and Tm-22 from tomato confer extreme resistance against Potato virus X (PVX) or tobamoviruses Tomato mosaic virus (ToMV) and Tobacco mosaic virus (TMV), respectively, with little or no induction of visible necrotic lesions [4,5]

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