Hydrogen sulfide and rhizobia synergistically regulate nitrogen (N) assimilation and remobilization during N deficiency-induced senescence in soybean

Hydrogen sulfide (H2S) is emerging as an important signalling molecule that regulates plant growth and abiotic stress responses. However, the roles of H2S in symbiotic nitrogen (N) assimilation and remobilization have not been characterized. Therefore, we examined how H2S influences the soybean (Glycine max)/rhizobia interaction in terms of symbiotic N fixation and mobilization during N deficiency-induced senescence. H2S enhanced biomass accumulation and delayed leaf senescence through effects on nodule numbers, leaf chlorophyll contents, leaf N resorption efficiency, and the N contents in different tissues. Moreover, grain numbers and yield were regulated by H2S and rhizobia, together with N accumulation in the organs, and N use efficiency. The synergistic effects of H2S and rhizobia were also demonstrated by effects on the enzyme activities, protein abundances, and gene expressions associated with N metabolism, and senescence-associated genes (SAGs) expression in soybeans grown under conditions of N deficiency. Taken together, these results show that H2S and rhizobia accelerate N assimilation and remobilization by regulation of the expression of SAGs during N deficiency-induced senescence. Thus, H2S enhances the vegetative and reproductive growth of soybean, presumably through interactions with rhizobia under conditions of N deficiency.