Kim Minyoung, Lee Jongchan, Heo Lynn, Han Sang-Wook
Department of Plant Science and Technology, Chung-Ang University, Anseong, South Korea.
Front Plant Sci. 2020 Sep 25;11:569552. doi: 10.3389/fpls.2020.569552. eCollection 2020.
() is a plant pathogenic bacterium that causes bacterial fruit blotch (BFB) in cucurbit crops. Despite its importance in the cucurbit industry, resistant cultivars/lines against BFB have not yet been identified. Therefore, there is a need to characterize the virulence factors/mechanisms in to control the disease. Chorismate mutase, a key enzyme in the shikimate pathway, produces aromatic amino acids. Here, we report the functions of putative bifunctional chorismate mutase/prephenate dehydratase in (CmpAc) determined by proteomic analysis and phenotypic assays. strain lacking CmpAc, (EV), were significantly less virulent on watermelon in the germinated-seed inoculation and leaf infiltration assays. Sequence analysis revealed that CmpAc possesses two distinct domains: chorismate mutase and prephenate dehydratase, indicating that CmpAc is a bifunctional protein. Auxotrophic assays demonstrated that CmpAc is required for the biosynthesis of phenylalanine, but not tyrosine. The comparative proteomic analysis revealed that CmpAc is mostly involved in cell wall/membrane/envelop biogenesis. Furthermore, (EV) showed reduced twitching halo production and enhanced biofilm formation. In addition, (EV) was less tolerant to osmotic stress but more tolerant to antibiotics (polymyxin B). Thus, our study provides new insights into the functions of a putative bifunctional protein related to virulence in .
（）是一种植物致病细菌，可导致葫芦科作物发生细菌性果斑病（BFB）。尽管其在葫芦科产业中具有重要性，但尚未鉴定出对BFB具有抗性的品种/品系。因此，有必要对（）中的毒力因子/机制进行表征以控制该疾病。分支酸变位酶是莽草酸途径中的关键酶，可产生芳香族氨基酸。在此，我们报告了通过蛋白质组学分析和表型分析确定的（）中假定的双功能分支酸变位酶/预苯酸脱水酶（CmpAc）的功能。在发芽种子接种和叶片浸润试验中，缺乏CmpAc的（）菌株（EV）对西瓜的毒力明显较低。序列分析表明，CmpAc具有两个不同的结构域：分支酸变位酶和预苯酸脱水酶，表明CmpAc是一种双功能蛋白。营养缺陷型分析表明，CmpAc是苯丙氨酸生物合成所必需的，但不是酪氨酸生物合成所必需的。比较蛋白质组学分析表明，CmpAc主要参与细胞壁/膜/包膜生物合成。此外，（EV）显示出抽搐晕圈产生减少和生物膜形成增强。此外，（EV）对渗透胁迫的耐受性较低，但对抗生素（多粘菌素B）的耐受性较高。因此，我们的研究为（）中与毒力相关的假定双功能蛋白的功能提供了新的见解。
