Winans S C, Mantis N J, Chen C Y, Chang C H, Han D C
Section of Microbiology, Cornell University, Ithaca, NY 14853.
Res Microbiol. 1994 Jun-Aug;145(5-6):461-73. doi: 10.1016/0923-2508(94)90095-7.
Agrobacterium tumefaciens contains about 25 vir genes localized on a 200-kb tumour-inducing (Ti) plasmid that direct a conjugation-like transfer of tumorigenic DNA from the bacterium to the nuclei of infected plant cells. These genes are strongly and coordinately induced during infection in response to three different classes of stimuli which are thought to be key chemical features of a typical wound site. These stimuli are (i) guaiacol and syringol derivatives such as acetosyringone, (ii) sugars such as glucose and glucuronic acid, and (iii) acidic pH. The sensing of these compounds is carried out by the VirA, VirG and ChvE proteins. VirA is a four-domain histidine protein kinase, while VirG is a transcriptional activator which is activated by VirA-mediated phosphorylation. ChvE is a chromosomally encoded periplasmic sugar binding protein which is required for sensing sugars but dispensable for sensing the other two stimuli. Here we will review the nature of these chemical stimuli, the structure and function of the three regulatory proteins, their similarity to sensors found in human and animal pathogens, the factors influencing their pool size, and their role in the host range of different strains of A. tumefaciens.
根癌土壤杆菌含有约25个vir基因，这些基因定位在一个200 kb的致瘤（Ti）质粒上，该质粒指导致瘤DNA从细菌向受感染植物细胞核进行类似接合的转移。在感染过程中，这些基因会响应三类不同的刺激而被强烈且协同诱导，这些刺激被认为是典型伤口部位的关键化学特征。这些刺激包括：（i）愈创木酚和丁香酚衍生物，如乙酰丁香酮；（ii）糖类，如葡萄糖和葡萄糖醛酸；（iii）酸性pH值。这些化合物的感知由VirA、VirG和ChvE蛋白完成。VirA是一种具有四个结构域的组氨酸蛋白激酶，而VirG是一种转录激活因子，它通过VirA介导的磷酸化作用被激活。ChvE是一种染色体编码的周质糖结合蛋白，它对于感知糖类是必需的，但对于感知其他两种刺激则是可有可无的。在这里，我们将综述这些化学刺激的性质、三种调节蛋白的结构和功能、它们与人和动物病原体中发现的传感器的相似性、影响它们数量的因素，以及它们在不同根癌土壤杆菌菌株宿主范围中的作用。
