背景黄单胞菌属细菌在各种作物中引起经济上重要的疾病。它们的毒力依赖于III型效应子(T3Es)通过III型分泌系统(T3SS)易位到植物细胞中,由主响应调节器HrpG调节的过程。尽管HrpG已经研究了二十多年,它在不同的黄单胞菌物种中的调节子,特别是在III型分泌之外,仍未研究。
结果:在这项研究中,我们进行了转录组测序,以探索17株黄单胞菌的HrpG调控子,包括六个物种和九个pathovars,每个都表现出不同的宿主和组织特异性。我们采用质粒携带的hrpG*的组成型表达,编码HrpG的组成型活性形式,诱导调节子。我们的发现揭示了跨菌株的HrpG*调节子的显著的种间和种内多样性。除了21个直接参与T3SS生物合成的基因,核心HrpG*调节子仅限于编码转录激活因子HrpX的五个额外基因,两种T3E蛋白XopR和XopL,大型设施超家族(MFS)运输车,和磷酸酶PhoC.有趣的是,参与趋化性的基因和编码具有碳水化合物活性和蛋白水解活性的酶的基因受到HrpG*的可变调节。
结论:HrpG*调节子的多样性表明,黄单胞菌中HrpG依赖性毒力可能通过几种不同的菌株特异性策略来实现,潜在地反映了对不同生态位的适应。这些发现增强了我们对HrpG在调节各种毒力和适应性途径中的复杂作用的理解。延伸到T3E和T3SS之外。
BACKGROUND: Bacteria of the genus Xanthomonas cause economically significant diseases in various crops. Their virulence is dependent on the translocation of type III effectors (T3Es) into plant cells by the type III secretion system (T3SS), a process regulated by the master response regulator HrpG. Although HrpG has been studied for over two decades, its regulon across diverse Xanthomonas species, particularly beyond type III secretion, remains understudied.
RESULTS: In this study, we conducted transcriptome sequencing to explore the HrpG regulons of 17 Xanthomonas strains, encompassing six species and nine pathovars, each exhibiting distinct host and tissue specificities. We employed constitutive expression of plasmid-borne hrpG*, which encodes a constitutively active form of HrpG, to induce the regulon. Our findings reveal substantial inter- and intra-specific diversity in the HrpG* regulons across the strains. Besides 21 genes directly involved in the biosynthesis of the T3SS, the core HrpG* regulon is limited to only five additional genes encoding the transcriptional activator HrpX, the two T3E proteins XopR and XopL, a major facility superfamily (MFS) transporter, and the phosphatase PhoC. Interestingly, genes involved in chemotaxis and genes encoding enzymes with carbohydrate-active and proteolytic activities are variably regulated by HrpG*.
CONCLUSIONS: The diversity in the HrpG* regulon suggests that HrpG-dependent virulence in Xanthomonas might be achieved through several distinct strain-specific strategies, potentially reflecting adaptation to diverse ecological niches. These findings enhance our understanding of the complex role of HrpG in regulating various virulence and adaptive pathways, extending beyond T3Es and the T3SS.