Leroux B, Yanofsky M F, Winans S C, Ward J E, Ziegler S F, Nester E W
EMBO J. 1987 Apr;6(4):849-56. doi: 10.1002/j.1460-2075.1987.tb04830.x.
The virulence (vir) region of Agrobacterium tumefaciens mediates the transfer of a defined segment of plasmid DNA (the T-DNA) into the plant genome. The vir genes are specifically induced by molecules produced by wounded plant cells, and virA is required for this induction. We have determined the nucleotide sequence of virA loci from limited (pTiAg162) and wide (pTiA6) host range tumor-inducing (Ti) plasmids, each of which encodes a single protein of 92,000 daltons. Using antibody directed against the virA gene product, we have localized the VirA protein to the bacterial inner membrane. VirA is homologous to at least four bacterial proteins which play a role in the transcriptional regulation of diverse families of genes. Based on its role in vir gene induction, homology to transcriptional regulators and membrane localization, we propose that VirA acts as an environmental sensor of plant-derived inducer molecules and transmits this information to the level of vir gene expression. The pTiAg162 virA locus was shown to be ineffective at directing vir gene induction, suggesting that this may in part contribute to the narrow host range conferred by this plasmid.
根癌土壤杆菌的毒性（vir）区域介导了一段特定的质粒DNA（T-DNA）转移到植物基因组中。vir基因由受伤植物细胞产生的分子特异性诱导，而virA是这种诱导所必需的。我们已经确定了来自有限宿主范围（pTiAg162）和广泛宿主范围（pTiA6）的致瘤（Ti）质粒的virA基因座的核苷酸序列，每个质粒都编码一种92,000道尔顿的单一蛋白质。使用针对virA基因产物的抗体，我们已将VirA蛋白定位到细菌内膜。VirA与至少四种在不同基因家族的转录调控中起作用的细菌蛋白同源。基于其在vir基因诱导中的作用、与转录调节因子的同源性以及膜定位，我们提出VirA作为植物来源诱导分子的环境传感器，并将此信息传递到vir基因表达水平。pTiAg162 virA基因座被证明在指导vir基因诱导方面无效，这表明这可能部分导致了该质粒赋予的狭窄宿主范围。
