MCHK_7135基因在华癸中慢生根瘤菌共生固氮中的功能

Function of MCHK_7135 gene in symbiotic nitrogen fixation of Mesorhizobium huakuii

为研究MCHK_7135基因在根瘤菌与宿主植物共生固氮中的功能,用同源重组的方法构建了MCHK_7135基因的突变体及回补菌株,对突变菌株和回补菌株在人工培养条件以及与宿主植物紫云英共生下的各项表型进行了考察,结果显示:与野生型菌株相比,突变菌株对氧胁迫的敏感性增强;接种突变株的紫云英长势矮小,侵染线及根瘤原基数目减少,根瘤数量少,固氮酶活性低,而向突变菌株导入完整MCHK_7135基因后,各项共生表型得到不同程度恢复。研究结果表明,华癸中慢生根瘤菌的过氧化物还原酶基因MCHK_7135基因在根瘤菌与宿主植物共生固氮的过程中具有重要功能。

In the previous studies,the global transcriptome databases of Mesorhizobium huakuii 7653R in free living and in symbiotic condition were constructed respectively.Some differential expression genes in free living and symbiotic condition were identified with RNA-Seq and Microarray.Among these genes,MCHK_7135 belongs to the peroxiredoxin(Prxs)family.Its expression was significantly up-regu⁃lated at the stage of symbiotic nitrogen fixation.In this article,the replacement mutants and complementary strains of MCHK_7135 were constructed by homologous recombination to study the function of MCHK_7135 gene in symbiotic nitrogen fixation between rhizobia and host plants.The phenotypes of mutant and complementary strains were investigated under free living and symbiotic condition with Astragalus sinicus.Results showed that the mutant strain of MCHK_7135 gene was more sensitive to H2O2 stress compare with the wild-type strain.The growth of A.sinicus plant inoculated with the mutant was inhibited,the num⁃ber of infect thread and nodule primordia decreased,the number of nodule was small,and the activity of ni⁃trogenase was low.However,when the mutant strain was complemented by complete MCHK_7135 gene,some symbiotic phenotypes were restored to different degree.It is indicated that the peroxiredoxin gene MCHK_7135 of M.huakuii plays an important role in the symbiotic nitrogen fixation between rhizobia and host plants.