YggS Encoding Pyridoxal 5'-Phosphate Binding Protein Is Required for Acidovorax citrulli Virulence.

Yuanjie Wang,Baohui Chen,Yiyang Liu,Yajie Liao,Liming Xia,Weirong Gong,Yuqiang Zhao,Lin Chen,Baishi Hu,Yanli Tian

doi:10.3389/fmicb.2021.783862

Abstract

Bacterial fruit blotch, caused by seed-borne pathogen Acidovorax citrulli, poses a serious threat to the production of cucurbits globally. Although the disease can cause substantial economic losses, limited information is available about the molecular mechanisms of virulence. This study identified that, a random transposon insertion mutant impaired in the ability to elicit a hypersensitive response on tobacco. The disrupted gene in this mutant was determined to be Aave_0638, which is predicted to encode a YggS family pyridoxal phosphate-dependent enzyme. YggS is a highly conserved protein among multiple organisms, and is responsible for maintaining the homeostasis of pyridoxal 5′-phosphate and amino acids in cells. yggS deletion mutant of A. citrulli strain XjL12 displayed attenuated virulence, delayed hypersensitive response, less tolerance to H2O2 and pyridoxine, increased sensitivity to antibiotic β-chloro-D-alanine, and reduced swimming. In addition, RNA-Seq analysis demonstrated that yggS was involved in regulating the expression of certain pathogenicity-associated genes related to secretion, motility, quorum sensing and oxidative stress response. Importantly, YggS significantly affected type III secretion system and its effectors in vitro. Collectively, our results suggest that YggS is indispensable for A.citrulli virulence and expands the role of YggS in the biological processes.

Highlights

Bacterial fruit blotch (BFB), a seed-borne disease caused by Acidovorax citrulli, has caused substantial economic losses to the global cucurbit industry (Schaad et al, 1978, 2008; Willems et al, 1992)
Multiple sequence alignment shows that the amino acid sequence of YggS from A. citrulli has high identity among the tested bacteria including E. coli (Figure 1A)
We observed the position of yggS on genome and found that yggS and pilT, encoding yggS Affected Acidovorax citrulli Virulence

Summary

Introduction

Bacterial fruit blotch (BFB), a seed-borne disease caused by Acidovorax citrulli, has caused substantial economic losses to the global cucurbit industry (especially melon and watermelon) (Schaad et al, 1978, 2008; Willems et al, 1992). In addition to the above-mentioned classical apparatus related to bacterial pathogenicity, other factors such as ferric uptake regulator (FurA) (Liu et al, 2019), quorum sensing (QS) (Wang et al, 2016), and bifunctional chorismate mutase/prephenate dehydratase (Cmp) (Kim et al, 2020), have been reported to contribute to A. citrulli virulence. These advances have improved our understanding of the complex pathogenic mechanisms

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