CRb and PbBa8.1 Synergically Increases Resistant Genes Expression upon Infection of Plasmodiophora brassicae in Brassica napus.

Nadil Shah,Li Zhu,Zongxiang Zhan,Ju Liu,Xueqing Zhou,Ping Qin,Fan Huang,Chunyu Zhang,Qian Li,Qiang Xu,Wenlin Yu

doi:10.3390/genes11020202

Abstract

PbBa8.1 and CRb are two clubroot-resistant genes that are important for canola breeding in China. Previously, we combined these resistant genes and developed a pyramid-based, homozygous recurrent inbred line (618R), the results of which showed strong resistance to Plasmodiophora brassicae field isolates; however, the genetic mechanisms of resistance were unclear. In the present work, we conducted comparative RNA sequencing (RNA-Seq) analysis between 618R and its parental lines (305R and 409R) in order to uncover the transcriptomic response of the superior defense mechanisms of 618R and to determine how these two different resistant genes coordinate with each other. Here, we elucidated that the number and expression of differentially expressed genes (DEGs) in 618R are significantly higher than in the parental lines, and PbBa8.1 shares more DEGs and plays a dominant role in the pyramided line. The common DEGs among the lines largely exhibit non-additive expression patterns and enrichment in resistance pathways. Among the enriched pathways, plant–pathogen interaction, plant hormone signaling transduction, and secondary metabolites are the key observation. However, the expressions of the salicylic acid (SA) signaling pathway and reactive oxygen species (ROS) appear to be crucial regulatory components in defense response. Our findings provide comprehensive transcriptomic insight into understanding the interactions of resistance gene pyramids in single lines and can facilitate the breeding of improved resistance in Brassica napus.

Highlights

Rapeseed (Brassica napus) is the second most important oilseed crop in the world, providing edible oil and raw material for bio-energy applications [1]
To analyze the comparative transcriptome level changes in 305R, 409R, and 618R after P. brassicae inoculation, Illumina sequencing was conducted via RNA sequencing (RNA-Seq) of the roots of these three lines before and after artificial pathogen inoculation
This insight revealed plays a dominant role, with a higher number of non-additive genes than the pyramided line. This that the pyramided line strongly triggers multiple resistance pathways, including the plant–pathogen insight revealed that the pyramided line strongly triggers multiple resistance pathways, including interaction, plant hormone signal transduction, secondary metabolites, transcription factors, and other the plant–pathogen interaction, plant hormone signal transduction, secondary metabolites, processes, indicating that the plant has responded via a multi-gene network to pathogen attack

Summary

Introduction

Rapeseed (Brassica napus) is the second most important oilseed crop in the world, providing edible oil and raw material for bio-energy applications [1]. China is the second-largest producer of rapeseed, which is the fourth-largest crop in this country after rice, wheat, and maize [2]. Plasmodiophora brassicae (P. brassicae), which causes clubroot disease, is one of the most serious threats to B. napus production worldwide, as well as in China. From Taiwan and Fujian in 1912 and 1947, respectively, and later in Jiangxi Province, the pathogen has rapidly spread to other parts of the country, causing severe annual losses of cruciferous crops. The pathogen has three life-cycle stages, namely, the resting spore stage, root hair infection stage, and cortex infection stage [6]. The development and cultivation of resistant varieties are the most economical and effective approaches to control clubroot disease

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Conclusion