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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >VirA and VirG activate the Ti plasmid repABC operon, elevating plasmid copy number in response to wound-released chemical signals.
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VirA and VirG activate the Ti plasmid repABC operon, elevating plasmid copy number in response to wound-released chemical signals.

机译：VirA和VirG激活Ti质粒repABC操纵子，响应伤口释放的化学信号而提高质粒拷贝数。

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摘要

The vir genes of Agrobacterium tumefaciens tumor-inducing (Ti) plasmids direct the transfer of oncogenic portion of the Ti (tumor-inducing) plasmid that is transferred to plant cells (T-DNA) into plant cells and are coordinately induced by plant-released phenolic chemical signals. We have used DNA microarrays, representing all genes of the octopine- and nopaline-type Ti plasmids, to identify all Ti-plasmid-encoded genes in the vir regulons of both plasmids. Acetosyringone (AS) induced the expression of all known members of the vir regulons, as well as a small number of additional genes. Unexpectedly, AS also caused a modest induction of virtually every Ti plasmid gene. This suggested that the copy number of the Ti plasmid might increase in response to AS, a hypothesis confirmed by DNA dot blotting. VirA and VirG were the only Vir proteins required for this copy number increase. Promoter resections and primer extension analysis of the repABC promoter region showed that expression of the promoter closestto repA (promoter P4) was induced by AS. We also identified a sequence resembling a consensus VirG-binding motif approximately 70 nucleotides upstream from the P4 transcription start site. Mutating this sequence blocked the AS-induced copy number increase of a RepABC-dependent miniplasmid, indicating that phospho-VirG increases copy number solely by enhancing repABC expression.
机译：根癌土壤杆菌（Agrobacterium tumefaciens）肿瘤诱导（Ti）质粒的vir基因指导将Ti（肿瘤诱导）质粒的致癌部分转移到植物细胞（T-DNA）中，并通过植物释放来协调诱导酚类化学信号。我们已经使用代表章鱼碱型和胭脂碱型Ti质粒的所有基因的DNA微阵列来鉴定两个质粒的vir调控区中所有Ti质粒编码的基因。乙酰丁香酮（AS）诱导vir调节子的所有已知成员以及少量其他基因的表达。出乎意料的是，AS实际上也引起了几乎每个Ti质粒基因的适度诱导。这表明Ti质粒的拷贝数可能会随着对AS的增加而增加，这一假设已被DNA点印迹证实。 VirA和VirG是增加拷贝数所需的唯一Vir蛋白。 repABC启动子区域的启动子切除和引物延伸分析表明，AS诱导了最接近repA的启动子（启动子P4）的表达。我们还鉴定了一个序列，该序列类似于一个共有的VirG结合基序，距P4转录起始位点上游约70个核苷酸。突变此序列可阻止RepABC依赖的小质粒的AS诱导的拷贝数增加，表明磷酸-VirG仅通过增强repABC表达而增加了拷贝数。

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