Biocatalysts Laboratory, Department of Agricultural Microbiology, Directorate of Natural Resource Management, Tamil Nadu Agricultural University, Coimbatore, 641 003, India.
Centre for Water Resources Development and Management, Kozhikode, India.
BMC Microbiol. 2023 Oct 5;23(1):284. doi: 10.1186/s12866-023-03028-z.
Secretome analysis is a valuable tool to study host-pathogen protein interactions and to identify new proteins that are important for plant health. Microbial signatures elicit defense responses in plants, and by that, the plant immune system gets triggered prior to pathogen infection. Functional properties of secretory proteins from Xanthomonas axonopodis pv. dieffenbachiae (Xad1) involved in priming plant immunity was evaluated.
In this study, the secretome of Xad1 was analyzed under host plant extract-induced conditions, and mass spectroscopic analysis of differentially expressed protein was identified as plant-defense-activating protein viz., flagellin C (FliC). The flagellin and Flg22 peptides both elicited hypersensitive reaction (HR) in non-host tobacco, activated reactive oxygen species (ROS) scavenging enzymes, and increased pathogenesis-related (PR) gene expression viz., NPR1, PR1, and down-regulation of PR2 (β-1,3-glucanase). Protein docking studies revealed the Flg22 epitope of Xad1, a 22 amino acid peptide region in FliC that recognizes plant receptor FLS2 to initiate downstream defense signaling.
The flagellin or the Flg22 peptide from Xad1 was efficient in eliciting an HR in tobacco via salicylic acid (SA)-mediated defense signaling that subsequently triggers systemic immune response epigenetically. The insights from this study can be used for the development of bio-based products (small PAMPs) for plant immunity and health.
分泌组分析是研究宿主-病原体蛋白相互作用和鉴定对植物健康重要的新蛋白的有价值的工具。微生物特征会在植物中引发防御反应，从而在病原体感染之前触发植物免疫系统。本研究评估了参与植物免疫引发的黄单胞菌 axonopodis pv. dieffenbachiae（Xad1）分泌蛋白的功能特性。
在这项研究中，分析了在宿主植物提取物诱导条件下 Xad1 的分泌组，差异表达蛋白的质谱分析被鉴定为植物防御激活蛋白，即鞭毛蛋白 C（FliC）。鞭毛蛋白和 Flg22 肽都在非宿主烟草中引发过敏反应（HR），激活活性氧（ROS）清除酶，并增加病程相关（PR）基因表达，即 NPR1、PR1 和下调 PR2（β-1,3-葡聚糖酶）。蛋白质对接研究表明，Xad1 的 Flg22 表位是 FliC 中的 22 个氨基酸肽区域，它识别植物受体 FLS2 以启动下游防御信号。
Xad1 的鞭毛蛋白或 Flg22 肽通过水杨酸（SA）介导的防御信号在烟草中有效引发 HR，随后引发系统免疫反应的表观遗传。本研究的见解可用于开发基于生物的产品（小 PAMPs）用于植物免疫和健康。
