Abstract：
Ralstonia solanacearum is a devastating phytopathogen infecting a broad range of economically important crops. Phosphate (Pi) homeostasis and assimilation play a critical role in the environmental adaptation and pathogenicity of many bacteria. However, the Pi assimilation regulatory mechanism of R. solanacearum remains unknown. This study revealed that R. solanacearum pstSCAB-phoU-phoBR operon expression is sensitive to extracellular Pi concentration, with higher expression under Pi-limiting conditions. The PhoB-PhoR fine-tunes the Pi-responsive expression of the Pho regulon genes, demonstrating its pivotal role in Pi assimilation. By contrast, neither PhoB, PhoR, PhoU, nor PstS was found to be essential for virulence on tomato plants. Surprisingly, the PhoB regulon is activated in a Pi-abundant rich medium. Results showed that histidine kinase VsrB, which is known for the exopolysaccharide production regulation, partially mediates PhoB activation in the Pi-abundant rich medium. The 271 histidine of VsrB is vital for this activation. This cross-activation mechanism between the VsrB and PhoB-PhoR systems suggests the carbohydrate-Pi metabolism coordination in R. solanacearum. Overall, this research provides new insights into the complex regulatory interplay between Pi metabolism and growth in R. solanacearum.
摘要：
青枯雷尔氏菌是一种破坏性的植物病原体，感染了广泛的经济上重要的作物。磷酸盐（Pi）稳态和同化在许多细菌的环境适应和致病性中起关键作用。然而,青枯菌的Pi同化调节机制尚不清楚。这项研究表明，青枯树pstSCAB-phoU-phoBR操纵子的表达对细胞外Pi浓度敏感，在Pi限制条件下具有较高的表达。PhoB-PhoR微调Pho调节子基因的Pi响应表达，展示了它在Pi同化中的关键作用。相比之下,PhoB都不是,PhoR,PhoU,也没有发现PstS对番茄植物的毒力至关重要。令人惊讶的是,PhoB调节子在Pi丰富的富介质中被激活。结果表明,组氨酸激酶VsrB,这是众所周知的外多糖生产调控，在Pi丰富的富培养基中部分介导PhoB活化。VsrB的271组氨酸对于这种激活是至关重要的。VsrB和PhoB-PhoR系统之间的这种交叉激活机制表明，在青枯菌中碳水化合物-Pi代谢协调。总的来说,这项研究提供了新的见解Pi代谢和生长之间复杂的调节相互作用。
