Enhancement technology of bacterial infection by rhizobitoxine

本论文研究了埃氏慢生根瘤菌（Bradyrhizobium elkanii）中根瘤毒素的生物合成途径及其功能。此外，我们研究了是否能够产生根瘤毒素可以提高根瘤菌共生和农杆菌介导的转化。对根瘤菌毒素生物合成基因的序列测定和突变分析表明，在埃氏慢生根瘤菌中，至少rtxA和rtxC是根瘤菌毒素生物合成所必需的。乙烯前体和抑制剂的应用乙烯的生物合成和感知表明，乙烯介导的信号通路参与的结瘤过程中，即使在有限的结瘤包括百脉根和Macroptilium atropurpureum。根瘤菌毒素竞争性抑制寄主植物乙烯生物合成途径中的1-氨基环丙烷-1-羧酸合酶，增强了B的竞争性。elkanii在M.紫黑色。有趣的是，根瘤菌素增强竞争性絮凝发生在絮凝的时间过程中的后期阶段。我们一直试图赋予B产生根瘤毒素的能力。elkanii通过携带rtxAC的质粒感染其它革兰阴性菌。

We have investigated rhizobitoxine biosynthetic pathway and the function in Bradyrhizobium elkanii. In addition, we examined whether the ability to produce rhizobitoxine may improve rhizobial symbiosis and Agrobacterium-mediated transformation. DNA sequence and mutational analysis of rhizobitoxine biosynthetic genes revealed that at least rtxA and rtxC are requiered for rhizobitoxine biosynthesis in Bradyrhizobium elkanii. Application of ethylene precursor and inhibitors for ethylene biosynthesis and perception suggested that an ethylene-mediated signaling pathway is involved in the nodulation process even in the determinate nodulators including Lotus japonicus and Macroptilium atropurpureum. Rhizobitoxine competitively inhibited 1-aminocyclopropane-1-carboxylate synthase in ethylene biosynthetic pathway of host plants, and enhanced nodulation and competitiveness of B. elkanii on M. atropurpureum. Interestingly, Rhizobitoxine enhancement of competitive nodulation occurred at a late stage in the time-course of nodulation. We have been trying to confer the ability to produce rhizobitoxine of B. elkanii into other gram-negative bacteria by plasmids carrying rtxAC.