Persulfidation of plant and bacteroid proteins is involved in legume nodule development and senescence

Legumes establish symbiosis with soil rhizobia forming root nodules that fix atmospheric nitrogen. The central role of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in nodule biology has been clearly established. Recently, hydrogen sulfide (H2S) and other reactive sulfur species (RSS) have emerged as novel signaling molecules in animals and plants. A major mechanism by which ROS, RNS, and RSS fulfil their signaling role is the post-translational modification of proteins. To identify possible functions of H2S in nodule development and senescence, we used the tag-switch method to analyze quantitative changes in the persulfidation profile of common bean (Phaseolus vulgaris) nodules at different developmental stages. The proteomic analysis suggests that persulfidation plays a major regulatory role in plant and bacteroid metabolism and senescence. In addition, the effect of a H2S donor on several proteins involved in ROS and RNS homeostasis was investigated. The results obtained using nodule extracts and recombinant proteins suggest a crosstalk between H2S, ROS, and RNS, and a protective function of persulfidation on redox-sensitive enzymes from oxidative modifications that may cause enzyme inactivation. It is concluded that the general decrease of persulfidation levels observed in plant proteins of aging nodules is one of the mechanisms that cause the disruption of redox homeostasis leading to senescence.