College of Agriculture, South China Agricultural University, Guangzhou, China.
College of Resources and Environment, Southwest University, Chongqing, China.
Mol Plant Pathol. 2020 Aug;21(8):1099-1110. doi: 10.1111/mpp.12963. Epub 2020 Jun 29.
Ralstonia solanacearum is an important bacterial pathogen that can infect a broad range of plants worldwide. A previous study showed that R. solanacearum could respond to exogenous organic acids or amino acids to modulate cell motility. However, it was unclear whether R. solanacearum uses these compounds to control infection. In this study, we found that R. solanacearum GMI1000 uses host plant metabolites to enhance the biosynthesis of virulence factors. We demonstrated that l-glutamic acid from host plants is the key active component associated with increased extracellular polysaccharide production, cellulase activity, swimming motility, and biofilm formation in R. solanacearum GMI1000. In addition, l-glutamic acid also promoted colonization of R. solanacearum cells in the roots and stems of tomato plants and accelerated disease incidence. Furthermore, genetic screening and biochemical analysis suggested that RS01577, a hybrid sensor histidine kinase/response regulator, is involved in l-glutamic acid signalling in R. solanacearum. Mutations in RS01577 and exogenous addition of l-glutamic acid to the GMI1000 wild-type strain had overlapping effects on both the transcriptome and biological functions of R. solanacearum, including on motility, biofilm formation, and virulence. Thus, our results have established a new interaction mechanism between R. solanacearum and host plants that highlights the complexity of the virulence regulation mechanism and may provide new insight into disease control.
青枯雷尔氏菌是一种重要的细菌病原体，可以感染全球范围内广泛的植物。先前的研究表明，青枯雷尔氏菌可以对外源有机酸或氨基酸做出响应，从而调节细胞运动性。然而，青枯雷尔氏菌是否利用这些化合物来控制感染尚不清楚。在本研究中，我们发现青枯雷尔氏菌 GMI1000 利用宿主植物代谢物来增强毒力因子的生物合成。我们证明，宿主植物来源的 l-谷氨酸是与增强胞外多糖产生、纤维素酶活性、泳动性和生物膜形成相关的关键活性成分。此外，l-谷氨酸还促进了青枯雷尔氏菌细胞在番茄植株根和茎中的定殖，并加速了疾病的发生。此外，遗传筛选和生化分析表明，RS01577，一种混合传感器组氨酸激酶/反应调节蛋白，参与了青枯雷尔氏菌中 l-谷氨酸信号转导。RS01577 的突变和 l-谷氨酸的外源添加对 GMI1000 野生型菌株的转录组和生物学功能都有重叠的影响，包括运动性、生物膜形成和毒力。因此，我们的研究结果建立了青枯雷尔氏菌与宿主植物之间的一种新的相互作用机制，突出了毒力调控机制的复杂性，并可能为疾病控制提供新的见解。
