Proteomic and Mutant Analysis of Hydrogenase Maturation Protein Gene in Symbiotic Nitrogen Fixation of .

yet important redox reaction between protons and electrons and H, thus mediating symbiotic interactions. The contribution of to this symbiosis and anti-oxidative damage was investigated using the (encoding maturation protein) mutant. The mutant grew a little faster than its parental 7653R and displayed decreased antioxidative capacity under HO-induced oxidative damage. Real-time quantitative PCR showed that gene expression is significantly up-regulated in all the detected stages of nodule development. Although the mutant can form nodules, the symbiotic ability was severely impaired, which led to an abnormal nodulation phenotype coupled to a 47% reduction in nitrogen fixation capacity. This phenotype was linked to the formation of smaller abnormal nodules containing disintegrating and prematurely senescent bacteroids. Proteomics analysis allowed a total of ninety differentially expressed proteins (fold change > 1.5 or <0.67, < 0.05) to be identified. Of these proteins, 21 are related to stress response and virulence, 21 are involved in transporter activity, and 18 are involved in energy and nitrogen metabolism. Overall, the HypE protein is essential for symbiotic nitrogen fixation, playing independent roles in and detoxification, and in the control of bacteroid differentiation and senescence.