pSymA-Dependent Mobilization of the Sinorhizobium meliloti pSymB Megaplasmid
pSymA-Dependent Mobilization of the Sinorhizobium meliloti pSymB Megaplasmid
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DOI：
10.1128/jb.00549-10
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发表时间：
2010-12-01
影响因子：
3.2
通讯作者：
Nogales, Joaquina
中科院分区：
文献类型：
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作者：
Blanca-Ordonez, Helena;Oliva-Garcia, Juan J.;Nogales, Joaquina
苜蓿中华根瘤菌 1021 携带两个大质粒，即 1,354 kb 的 pSymA 和 1,683 kb 的 pSymB，这对于与其豆科宿主建立共生至关重要，并且对于根际细菌的适应性也很重要。我们之前已经证明 pSymA 是可自我传播的，并且其接合功能受到转录抑制子 RctA 的调节。在这里，我们展示了 pSymB 的接合转移作为反式动员事件，需要 pSymA 编码的 IV 型分泌系统。 pSymB 携带一个功能性 oriT 和一个相邻的松弛酶基因 traA2，该基因也受到 rctA 的转录抑制。两种共生大质粒都需要松弛酶基因与其各自的oriT顺式排列，以实现最高的转移效率。
Sinorhizobium meliloti 1021 carries two megaplasmids, pSymA of 1,354 kb and pSymB of 1,683 kb, which are essential in establishing symbiosis with its legume hosts and important for bacterial fitness in the rhizosphere. We have previously shown that pSymA is self-transmissible and that its conjugal functions are regulated by the transcriptional repressor RctA. Here, we show conjugal transfer of pSymB as an in trans mobilization event that requires the type IV secretion system encoded by pSymA. pSymB carries a functional oriT and an adjacent relaxase gene, traA2, that is also transcriptionally repressed by rctA. Both symbiotic megaplasmids would require the relaxase genes in cis with their respective oriTs to achieve the highest transfer efficiencies.