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 Ralstonia solanacearum, hereafter designated RsRsgA. Deletion of R. solanacearum rsgA or rbfA 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 rsgA mutants and rbfA mutants of Escherichia coli 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 R. solanacearum) both in vitro and in planta. Compared with the wild-type R. solanacearum strain, proliferation of the rsgA and rbfA 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 rsgA 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 rsgA mutant, some of which are responsible for R. solanacearum 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 R. solanacearum.

中文翻译：

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RsRsgA的功能特征用于核糖体生物合成和青枯雷尔氏菌中III型分泌系统的表达。

RsgA在许多细菌的30S亚基成熟中起着重要作用，有助于在核糖体生物合成的后期从30S亚基释放RbfA。在这里，我们从遗传上表征了RsgA在青枯雷尔氏菌中的功能角色，以下称为RsRsgA。番茄青枯菌rsgA或rbfA的缺失导致16S核糖体RNA明显缺乏，肉汤培养基中的生长显着减慢，营养受限培养基中的生长减少，这与大肠杆菌和其他细菌的rsgA突变体和rbfA突变体的表型相似。我们的基因表达研究表明，RsRsgA对于在体外和植物体内表达编码III型分泌系统（T3SS）（茄形红斑病菌的致病性决定因素）的基因都很重要。与野生型青枯菌相比，rsgA和rbfA突变体在烟叶中的增殖受到显着损害，而它们却无法从渗透叶迁移到烟草木质部的容器中，因此，这两个突变体未能在烟草植物中引起任何细菌性枯萎病。进一步揭示，与肉汤培养基相比，在营养有限的条件下，rsgA表达高度增强，并且RsRsgA通过PrhN-PrhG-HrpB途径影响T3SS表达。此外，在rsgA突变体中，III型效应子集的表达被大大削弱，其中的一些导致烟草中的R. solanacearum GMI1000引起超敏反应（HR），而HR诱导GMI1000并不需要RsRsgA。在烟叶中。