RNA-Seq reveals infection-related gene expression changes in Phytophthora capsici.

Xiao-Ren Chen,Yan-Peng Li,Jing-You Xu,Yu-Ping Xing,Yun-Hui Tong,Zhanjiang Liu

doi:10.1371/journal.pone.0074588

Abstract

Phytophthora capsici is a soilborne plant pathogen capable of infecting a wide range of plants, including many solanaceous crops. However, genetic resistance and fungicides often fail to manage P. capsici due to limited knowledge on the molecular biology and basis of P. capsici pathogenicity. To begin to rectify this situation, Illumina RNA-Seq was used to perform massively parallel sequencing of three cDNA samples derived from P. capsici mycelia (MY), zoospores (ZO) and germinating cysts with germ tubes (GC). Over 11 million reads were generated for each cDNA library analyzed. After read mapping to the gene models of P. capsici reference genome, 13,901, 14,633 and 14,695 putative genes were identified from the reads of the MY, ZO and GC libraries, respectively. Comparative analysis between two of samples showed major differences between the expressed gene content of MY, ZO and GC stages. A large number of genes associated with specific stages and pathogenicity were identified, including 98 predicted effector genes. The transcriptional levels of 19 effector genes during the developmental and host infection stages of P. capsici were validated by RT-PCR. Ectopic expression in Nicotiana benthamiana showed that P. capsici RXLR and Crinkler effectors can suppress host cell death triggered by diverse elicitors including P. capsici elicitin and NLP effectors. This study provides a first look at the transcriptome and effector arsenal of P. capsici during the important pre-infection stages.

Highlights

It has been found that more than 80 species of the genus Phytophthora can cause tens of billions of dollars of damage each year to a wide variety of agriculturally and ornamentally important crops worldwide [1,2]
Gene expression profiling using Illumina sequencing To understand the molecular bases of pathogenicity of P. capsici, three cDNA libraries representing mycelia grown in V8 liquid medium (MY), swimming zoospores (ZO) and germinating cysts with germ tubes (GC) were constructed
We used a cellophane membrane placed on the host leaf as a surface for the induction of cyst germination in order to carry out molecular investigation of the early infection events by P. capsici but without the involvement of plant biomass into later processing

Summary

Introduction

It has been found that more than 80 species of the genus Phytophthora can cause tens of billions of dollars of damage each year to a wide variety of agriculturally and ornamentally important crops worldwide [1,2]. They cause devastating plant diseases in forests, leading to severe losses [3]. A series of cell types are formed prior to host cell penetration, including sporangia, zoospores, cysts, and germinating cysts with germ tubes, all of which are important for plant infection and disease development [5]. The unraveling of the molecular processes regulating the life cycle of Phytophthora is important to identify determinants of pathogenesis and develop appropriate control strategies

Methods

Results

Discussion

Conclusion