Indoleacetic acid, a product of transferred DNA, inhibits vir gene expression and growth of Agrobacterium tumefaciens C58
Indoleacetic acid, a product of transferred DNA, inhibits vir gene expression and growth of Agrobacterium tumefaciens C58
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DOI：
10.1073/pnas.0600366103
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发表时间：
2006-03-21
影响因子：
11.1
通讯作者：
Nester, EW
中科院分区：
文献类型：
--
作者：
Liu, P;Nester, EW
根癌农杆菌通过将其肿瘤诱导质粒片段转移到植物细胞中来诱导冠瘿瘤。这种转移的DNA编码吲哚乙酸（IAA）和细胞分裂素的合成，它们的过量产生导致肿瘤形成。这种转移是由一个双组分调节系统启动的，VirA/G识别植物根际中的植物信号分子并激活肿瘤诱导质粒上的调节子，这是DNA和蛋白质加工和转移所必需的。虽然对vir基因的激活有很多了解，但对vir基因调节子在植物细胞转化后是否或如何失活却一无所知。据推测，就像只有当植物处于直接环境中时才存在激活vir基因调节子的机制一样，一旦完成了将DNA转移到植物细胞中的使命，就应该存在使同一调节子失活的机制。我们现在表明，IAA灭活病毒基因表达的诱导酚类化合物乙酰丁香酮竞争与病毒A的相互作用。IAA不抑制含有组成型传感器virA基因座的细胞中的vir基因，所述组成型传感器virA基因座不需要任何信号分子被磷酸化。在较高浓度下，IAA抑制农杆菌和许多其他植物相关细菌的生长，但不抑制占据其他生态位的细菌的生长。这些观察结果提供了vir基因激活和失活循环中缺失的环节。
Agrobacterium tumefaciens induces crown gall tumors by transferring a piece of its tumor-inducing plasmid into plant cells. This transferred DNA encodes the synthesis of indole acetic acid (IAA) and cytokinin, and their overproduction results in tumor formation. The transfer is initiated by a two-component regulatory system, VirA/G recognizing plant signal molecules in the plant rhizosphere and activating a regulon on the tumor-inducing plasmid, which is required for the processing and transfer of DNA and protein. Although a great deal is known about vir gene activation, nothing is known about whether or how the vir gene regulon is inactivated after plant cell transformation. Presumably, just as a mechanism exists for activating the vir gene regulon only when a plant is in the immediate environment, a mechanism should exist for inactivating the same regulon once it has fulfilled its mission to transferred DNA into plant cells. We now show that IAA inactivates vir gene expression by competing with the inducing phenolic compound acetosyringone for interaction with VirA. IAA does not inhibit the vir genes in cells containing a constitutive sensor virA locus, which does not require any signal molecules to become phosphorylated. At higher concentrations, IAA inhibits the growth of Agrobacterium and many other plant-associated bacteria but not the growth of bacteria that occupy other ecological niches. These observations provide the missing link in the cycle of vir gene activation and inactivation.