Study Of Cysdn Genes In Different Rhizobium On Sulfur Assimilation Metabolic Regulation

Sulfur is an essential element in cells, and it plays an important role either in constituting the structure of the organism components or in the metabolic processes. cysDN gene is a widespread housekeeping gene regulating sulfate assimilation in the biological world, which encodes ATP sulfatease to catalyze the sulfate and adenosine triphosphate (ATP) to synthesize activated sulfur source adenosine phosphate sulfate (APS).In this work, cysDN genes encoding ATP sulfurylase in four different species of rhizobia(Sinorhizobium fredii WGF03, Sinorhizobium fredii HN01, Sinorhizobium meliloti14500and Bradyrhizobium japonicum15606) have been studied. cysDN deletion mutants of four strains were constructed using homologous double exchange method respectively, the utilization of sulfur source of mutants and the effects on symbiotic nitrogen fixation after inoculating soybean were studied.The experiments’results showed that the regulation of cysDN gene in four rhizobia strains has some differences. After cysDN gene mutation, S. fredii WGF03and S. fredii HN01can not grow on the medium with sodium sulfate as the sole sulfur source, while they can grow normally in other sulfur sources such as sodium sulfite, sodium thiosulfate and cysteine; S. meliloti14500mutant can grow on the medium with sodium sulfate as the sole sulfur source, but the growth only can reach1/3of the wild type strain; in B. japonicum15606, there was no obvious difference between the wild strain and the mutant in the growth situation in each medium with various sulfur sources. The wild strains and cysDN mutants of S.fredii HN014, S. meliloti14500, B. japonicum15606were innoculated to leguminous plants respectively, all the strains can form infection thread and symbiotic nodulation with the leguminous plants in about10days, but have differences in the nitrogen fixation efficiency. In S.fredii HN01and S. meliloti14500, the symbiotic nitrogen fixation efficiency of mutants significantly reduced, and that of B. japonicum15606mutants also declined to some extent. Combined with the bioinformatics analysis, a preliminary conclusion has been demonstrated that, cysDN gene has different regulation mechanism of sulfur assimilation metabolism in different rhizobia.