A Virulence Essential CRN Effector of Phytophthora capsici Suppresses Host Defense and Induces Cell Death in Plant Nucleus.

Joseph Juma Mafurah,Daolong Dou,Danyu Shen,Nasir Ahmed Rajput,Feng He,Meixiang Zhang,Yanyu Chen,Jing Xu,Tingyue Ye,Huifei Ma,Eliseo A Eugenin

doi:10.1371/journal.pone.0127965

Abstract

Phytophthora capsici is a soil-borne plant pathogen with a wide range of hosts. The pathogen secretes a large array of effectors during infection of host plants, including Crinkler (CRN) effectors. However, it remains largely unknown on the roles of these effectors in virulence especially in P. capsici. In this study, we identified a cell death-inducing CRN effector PcCRN4 using agroinfiltration approach. Transient expression of PcCRN4 gene induced cell death in N. benthamiana, N. tabacum and Solanum lycopersicum. Overexpression of the gene in N. benthamiana enhanced susceptibility to P. capsici. Subcellular localization results showed that PcCRN4 localized to the plant nucleus, and the localization was required for both of its cell death-inducing activity and virulent function. Silencing PcCRN4 gene in P. capsici significantly reduced pathogen virulence. The expression of the pathogenesis-related gene PR1b in N. benthamiana was significantly induced when plants were inoculated with PcCRN4-silenced P. capsici transformant compared to the wilt-type. Callose deposits were also abundant at sites inoculated with PcCRN4-silenced transformant, indicating that silencing of PcCRN4 in P. capsici reduced the ability of the pathogen to suppress plant defenses. Transcriptions of cell death-related genes were affected when PcCRN4-silenced line were inoculated on Arabidopsis thaliana, suggesting that PcCRN4 may induce cell death by manipulating cell death-related genes. Overall, our results demonstrate that PcCRN4 is a virulence essential effector and it needs target to the plant nucleus to suppress plant immune responses.

Highlights

During plant-pathogen interactions, pathogens secrete an array of effector proteins to aid infection and establishment of parasitic lifestyles by modulating host cell defenses [1,2,3]
Its homologs PsCRN63 from P. sojae and PiCRN2 from P. infestans have been shown to elicit cell death in N. benthamiana [16,18]
Oomycete CRN proteins were initially identified through their ability to induce crinkling and necrosis when expressed in plant tissue, this protein family is generally considered as a class of cell death (CD)-triggering effectors [16]

Summary

Introduction

During plant-pathogen interactions, pathogens secrete an array of effector proteins to aid infection and establishment of parasitic lifestyles by modulating host cell defenses [1,2,3]. The plant immune system and its interplay with pathogen effectors are widely illustrated as a four-stage zigzag. When plants are attacked by microbes, they recognize microbe or pathogen-associated molecular patterns (PAMPS) which elicits PAMP-triggered immunity (PTI). Effective microbes have evolved a huge and diverse effector repertoires to counter PTI by suppression and subsequently enhance susceptibility (Effector-triggered susceptibility, ETS) [1,4]. A dynamic interaction between host immune responses and pathogen effectors has been widely reported in different pathosystems [5,6]; and identifying pathogen effectors and discovering their functions have become as essential routes to understand pathogen establishment

Methods

Results

Conclusion