Regulatory Mechanisms of the Resistance to Common Bacterial Blight Revealed by Transcriptomic Analysis in Common Bean (Phaseolus vulgaris L.).

Penghui Yang,Yujie Chang,Shumin Wang,Jing Wu,Lanfen Wang

doi:10.3389/fpls.2021.800535

Abstract

Common bean blight (CBB), primarily caused by Xanthomonas axonopodis pv. phaseoli (Xap), is one of the most destructive diseases of common bean (Phaseolus vulgaris L.). The tepary bean genotype PI 319443 displays high resistance to Xap, and the common bean genotypes HR45 and Bilu display high resistance and susceptibility to Xap, respectively. To identify candidate genes related to Xap resistance, transcriptomic analysis was performed to compare gene expression levels with Xap inoculation at 0, 24, and 48 h post inoculation (hpi) among the three genotypes. A total of 1,146,009,876 high-quality clean reads were obtained. Differentially expressed gene (DEG) analysis showed that 1,688 DEGs responded to pathogen infection in the three genotypes. Weighted gene coexpression network analysis (WGCNA) was also performed to identify three modules highly correlated with Xap resistance, in which 334 DEGs were likely involved in Xap resistance. By combining differential expression analysis and WGCNA, 139 DEGs were identified as core resistance-responsive genes, including 18 genes encoding resistance (R) proteins, 19 genes belonging to transcription factor families, 63 genes encoding proteins with oxidoreductase activity, and 33 plant hormone signal transduction-related genes, which play important roles in the resistance to pathogen infection. The expression patterns of 20 DEGs were determined by quantitative real-time PCR (qRT-PCR) and confirmed the reliability of the RNA-seq results.

Highlights

Common bean (Phaseolus vulgaris L.), a legume that originated in the Americas, belongs to the Fabaceae family and is one of the most important edible legumes in the world (Schmutz et al, 2014; Brouwer et al, 2016; Rendón-Anaya et al, 2017)
The resistance and susceptibility phenotypes of the common bean and tepary bean genotypes HR45, PI 319443 and Bilu were demonstrated with bacterial growth and symptom development after inoculation with Xanthomonas axonopodis pv. phaseoli (Xap) strain XS2
The results of common bacterial disease resistance identification showed that at 7 dpi, the pathogenicity level in HR45 and PI 319443 was grade 1, and the main feature was that only mechanical damage appeared at the inoculation site without symptoms, while the pathogenicity level in Bilu was grade 6, and the main feature was that transparent water stains appeared at the inoculation site, surrounded by a yellow halo, and expanded to the surrounding area (Figure 1A)

Summary

Introduction

Common bean (Phaseolus vulgaris L.), a legume that originated in the Americas, belongs to the Fabaceae family and is one of the most important edible legumes in the world (Schmutz et al, 2014; Brouwer et al, 2016; Rendón-Anaya et al, 2017). The pathogenic bacterium Xff can be identified as it can produce a brown pigment in milk Tween (MT) agar medium (Sheppard et al, 2007) Both bacterial strains can produce the same disease characteristics and cause similar damage to plants, studies have shown that Xap is a major endemic disease in China (Xu et al, 2013). Screening resistant germplasm resources, exploring resistance genes and breeding disease resistant varieties are more effective and efficient methods of managing CBB

Methods

Results

Discussion

Conclusion