Transcriptome analysis of maize leaf systemic symptom infected by Bipolaris zeicola.

Ming Liu,Fuqiang Yin,Min Zhang,Kunhao Ye,Xiaofang Sun,Guoshu Gong,You Zhou,Cheng Qin,Jian Gao,Youju Zhang,Dawn Sywassink Luthe

doi:10.1371/journal.pone.0119858

Abstract

Bipolaris zeicola is a fungal pathogen that causes Northern corn leaf spot (NCLS), which is a serious foliar disease in maize and one of the most significant pathogens affecting global food security. Here, we report a genome-wide transcriptional profile analysis using next-generation sequencing (NGS) of maize leaf development after inoculation with B. zeicola. We performed High-Throughput Digital Gene Expression analysis to identify differentially expressed genes (DEGs) in resistant inbred Mo17 lines after infection with B. zeicola at four successive disease development stages—CP (contact period), PP (penetration period), IP (incubation period), and DP (disease period); the expression of the genes was compared with those in a CK (mock-treatment) control. In addition, a sensitive maize line (Zheng58) was used for the comparisons with the Mo17. Among all tested genes, 466 differentially expressed genes were identified in all libraries, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of these genes suggested that they are involved in many biological processes related to systemic symptom development, such as plant hormone signal transduction, starch and sucrose metabolism, phenylpropanoid biosynthesis and photosynthesis. Our systematic analysis provides comprehensive transcriptomic information regarding systemic symptom development in fungal-infected plants. This information will help in furthering our understanding of the detailed mechanisms of plant responses to fungal infection.

Highlights

The process of disease period was as follows: extensive mycelia colonized on leaf surface and the fungus appeared to have dissolved the cuticle as well as two suberized layers that indicated mechanical pressure has occurred during host cell wall (HCW) penetration
Northern corn leaf spot (NCLS), which is caused by the fungus B. zeicola (Nisikado) Shoemaker, is a serious foliar disease of maize that is distributed widely in maize-producing areas throughout the world
We mapped in detail the transcriptional changes that occur during leaf development in response to B. zeicola infection

Summary

Introduction

NCLS is an important factor limiting the production of corn; the harm caused is not less than that caused by Northern corn leaf blight or Southern corn leaf blight in some hilly and mountainous areas This is true especially in Sichuan Province, China, due to the lack of resistant cultivars and the temperate mountain climate, which favors the disease; this disease is not considered a serious problem for corn production in other countries. Race 1 is among the most destructive pathogens of maize and can kill susceptible maize plants at any stage of development [4], causing spotting of the leaf, sheath and the stalk and molding of the ear; this race has become more prevalent in China in recent years. Transcriptome Analysis of Maize Systemic Symptom by Bipolaris zeicola metabolism were suppressed during pathogenesis and that metabolic pathways and plant hormone signal transduction were significantly enhanced during pathogen infection. Our study provides insights that might help to reveal the molecular mechanism of systemic symptom development in maize, which would further our understanding of plant-pathogen interactions

Materials and Methods

Results

Discussion