<scp>l</scp>‐cysteine desulfhydrase‐related H₂S production is involved in <i>OsSE5</i>‐promoted ammonium tolerance in roots of <scp><i>Oryza sativa</i></scp>

Abstract

Abstract Previous studies revealed that rice heme oxygenase PHOTOPERIOD SENSITIVITY 5 (OsSE5) is involved in the regulation of tolerance to excess ammonium by enhancing antioxidant defence. In this study, the relationship between OsSE5 and hydrogen sulfide (H 2 S), a well‐known signalling molecule, was investigated. Results showed that NH 4 Cl triggered the induction of l ‐cysteine desulfhydrase ( l ‐DES)‐related H 2 S production in rice seedling roots. A H 2 S donor not only alleviated the excess ammonium‐triggered inhibition of root growth but also reduced endogenous ammonium, both of which were aggravated by hypotaurine (HT, a H 2 S scavenger) or dl ‐propargylglycine (PAG, a l ‐DES inhibitor). Nitrogen metabolism‐related enzymes were activated by H 2 S, thus resulting in the induction of amino acid synthesis and total nitrogen content. Interestingly, the activity of l ‐DES, as well as the enzymes involved in nitrogen metabolism, was significantly increased in the OsSE5‐ overexpression line ( 35S:OsSE5 ), whereas it impaired in the OsSE5‐ knockdown mutant ( OsSE5 ‐RNAi). The application of the HT/PAG or H 2 S donor could differentially block or rescue NH 4 Cl‐hyposensitivity or hypersensitivity phenotypes in 35S:OsSE5‐1 or OsSE5 ‐RNAi‐1 plants, with a concomitant modulation of nitrogen assimilation. Taken together, these results illustrated that H 2 S function as an indispensable positive regulator participated in OsSE5‐promoted ammonium tolerance, in which nitrogen metabolism was facilitated.