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

Bacterial fruit blotch, caused by seed-borne pathogen , 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 , 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. deletion mutant of strain XjL12 displayed attenuated virulence, delayed hypersensitive response, less tolerance to HO and pyridoxine, increased sensitivity to antibiotic β-chloro-D-alanine, and reduced swimming. In addition, RNA-Seq analysis demonstrated that 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 . Collectively, our results suggest that YggS is indispensable for virulence and expands the role of YggS in the biological processes.