Stachel S E, Zambryski P C
Cell. 1986 Aug 1;46(3):325-33. doi: 10.1016/0092-8674(86)90653-7.
The Ti plasmid vir loci of Agrobacterium tumefaciens are transcriptionally activated in response to signal molecules produced by plant cells to initiate the T-DNA transfer process. We show that the pTiA6 vir loci are organized as a single regulon whose induction by plants is controlled by virA and virG. Mutations in virA result in attenuated induction. This locus is constitutively transcribed and noninducible. Mutations in virG eliminate vir induction. This locus is constitutively transcribed, plant-inducible, and self-regulated in a complex fashion, and it produces two distinct and differentially regulated transcripts. virA is proposed to encode a transport protein for the plant signal molecule, and virG a positive regulatory protein that together with the plant molecule activates vir expression.
根癌土壤杆菌的Ti质粒毒性基因座会响应植物细胞产生的信号分子而被转录激活，从而启动T-DNA转移过程。我们发现，pTiA6毒性基因座被组织成一个单一的调节子，其由植物诱导受virA和virG控制。virA中的突变导致诱导减弱。该基因座组成型转录且不可诱导。virG中的突变消除了毒性诱导。该基因座组成型转录、受植物诱导且以复杂方式自我调节，并且产生两种不同且调节方式不同的转录本。有人提出virA编码植物信号分子的转运蛋白，而virG编码一种正调控蛋白，该蛋白与植物分子一起激活毒性表达。
