Identification of Key Residues Essential for the Activation of Plant Immunity by Subtilisin From Bacillus velezensis LJ02

• Published in: Frontiers in microbiology 2022-08, Vol.13, p.869596-869596
• Main Authors: Hu, Jianan, Chang, Ruokui, Yuan, Yujin, Li, Zhuoran, Wang, Yuanhong
• Format: Article
• Language: English
• Subjects: Bacillus velezensis LJ02; Botrytis cinerea; Microbiology; PAMP-triggered immunity; subtilisin point mutant; systemic acquired resistance
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2022.869596

Subtilisin, a serine protease, can trigger defense responses in a wide variety of plants, both locally and systemically, to protect against pathogens. However, key residues of subtilisin to improve resistance to plant diseases remain unknown. In this study, Nicotiana benthamiana ( N. benthamiana ) leaves expressing subtilisin from Bacillus velezensis LJ02 were shown to improve protection against Botrytis cinerea ( B. cinerea ). Furthermore, the underlying mechanism that LJ02 subtilisin improved the protective effect was explored, and the direct inhibitory effect of subtilisin on B. cinerea was excluded in vitro . Subsequently, reactive oxygen species (ROS) burst and upregulation of resistance-related genes in systemic leaves of N. benthamiana further verified that subtilisin could induce systemic protection against B. cinerea . G307A/T308A and S213A/L214A/G215A subtilisin significantly reduced the ability to resist B. cinerea infection in N. benthamiana . Furthermore, the ROS content and expression levels of resistance-related genes of both mutants were significantly decreased compared with that of wild-type subtilisin. This work identified key residues essential for the activation function of subtilisin plant immunity and was crucial in inducing plant defense responses against B. cinerea .