Persulfidation of Nitrate Reductase 2 Is Involved in l-Cysteine Desulfhydrase-Regulated Rice Drought Tolerance

Hydrogen sulfide (H(2)S) is an important signaling molecule that regulates diverse cellular signaling pathways through persulfidation. Our previous study revealed that H(2)S is involved in the improvement of rice drought tolerance. However, the corresponding enzymatic sources of H(2)S and its regulatory mechanism in response to drought stress are not clear. Here, we cloned and characterized a putative l-cysteine desulfhydrase (LCD) gene in rice, which encodes a protein possessing H(2)S-producing activity and was named OsLCD1. Overexpression of OsLCD1 results in enhanced H(2)S production, persulfidation of total soluble protein, and confers rice drought tolerance. Further, we found that nitrate reductase (NR) activity was decreased under drought stress, and the inhibition of NR activity was controlled by endogenous H(2)S production. Persulfidation of NIA2, an NR isoform responsible for the main NR activity, led to a decrease in total NR activity in rice. Furthermore, drought stress-triggered inhibition of NR activity and persulfidation of NIA2 was intensified in the OsLCD1 overexpression line. Phenotypical and molecular analysis revealed that mutation of NIA2 enhanced rice drought tolerance by activating the expression of genes encoding antioxidant enzymes and ABA-responsive genes. Taken together, our results showed the role of OsLCD1 in modulating H(2)S production and provided insight into H(2)S-regulated persulfidation of NIA2 in the control of rice drought stress.