College of Resources and Environment, Southwest University, Chongqing, China.
Faculty of Agriculture and Marine Science, Kochi University, Kochi, Japan.
Mol Plant Microbe Interact. 2020 Jul;33(7):972-981. doi: 10.1094/MPMI-10-19-0294-R. Epub 2020 Jun 1.
RsgA plays an important role in maturation of 30S subunit in many bacteria that assists in the release of RbfA from the 30S subunit during a late stage of ribosome biosynthesis. Here, we genetically characterized functional roles of RsgA in , hereafter designated RsRsgA. Deletion of or resulted in distinct deficiency of 16S ribosomal RNA, significantly slowed growth in broth medium, and diminished growth in nutrient-limited medium, which are similar as phenotypes of mutants and mutants of and other bacteria. Our gene-expression studies revealed that RsRsgA is important for expression of genes encoding the type III secretion system (T3SS) (a pathogenicity determinant of ) both in vitro and in planta. Compared with the wild-type strain, proliferation of the and mutants in tobacco leaves was significantly impaired, while they failed to migrate into tobacco xylem vessels from infiltrated leaves, and hence, these two mutants failed to cause any bacterial wilt disease in tobacco plants. It was further revealed that expression was highly enhanced under nutrient-limited conditions compared with that in broth medium and RsRsgA affects T3SS expression through the PrhN-PrhG-HrpB pathway. Moreover, expression of a subset of type III effectors was substantially impaired in the mutant, some of which are responsible for GMI1000 elicitation of a hypersensitive response (HR) in tobacco leaves, while RsRsgA is not required for HR elicitation of GMI1000 in tobacco leaves. All these results provide novel insights into understanding various biological functions of RsgA proteins and complex regulation on the T3SS in .
RsgA 在许多细菌的 30S 亚基成熟中发挥重要作用,它有助于在核糖体生物合成的晚期从 30S 亚基中释放 RbfA。在这里,我们通过遗传方法对 中的 RsgA 功能进行了表征,以下简称 RsRsgA。缺失 或 导致 16S 核糖体 RNA 明显缺乏,显著减缓了在肉汤培养基中的生长速度,并减少了在营养有限的培养基中的生长速度,这与 突变体和其他细菌的 突变体的表型相似。我们的基因表达研究表明,RsRsgA 对于编码 III 型分泌系统(T3SS)( 的致病性决定因素)的基因的表达在体外和体内都很重要。与野生型 菌株相比, 和 突变体在烟草叶片中的增殖受到严重损害,而它们无法从渗透叶片进入烟草木质部血管,因此,这两个突变体无法在烟草植物中引起任何细菌性萎蔫病。进一步表明,与在肉汤培养基中相比,营养有限条件下 的表达高度增强,并且 RsRsgA 通过 PrhN-PrhG-HrpB 途径影响 T3SS 的表达。此外, 突变体中一组 III 型效应子的表达受到严重损害,其中一些效应子负责 GMI1000 在烟草叶片中引发过敏反应(HR),而 RsRsgA 对于 GMI1000 在烟草叶片中引发 HR 并不必需。所有这些结果为理解 RsgA 蛋白的各种生物学功能和 T3SS 的复杂调控提供了新的见解。