Functional analysis of the role of hydrogen sulfide in the regulation of dark-induced leaf senescence in Arabidopsis

There is growing evidence that hydrogen sulfide (H(2)S) is involved in many physiological processes in plants, but the role of H(2)S in dark-induced leaf senescence remains unknown. In this work, we found that H(2)S not only inhibited chlorophyll degradation but also caused the accumulation of photoreactive pheide a in detached leaves under extended darkness. Despite this, transcript levels of senescence-associated genes (SAGs) were less affected in H(2)S-treated detached leaves compared with those in H(2)S-untreated detached leaves. Furthermore, cell death/rapid bleaching occurred in both H(2)S-treated detached and attached leaves after transfer from extended darkness to light. Unlike the lack of effect of H(2)S on SAG transcripts in darkened detached leaves, exogenous H(2)S induced higher SAG transcript levels in attached leaves than untreated attached leaves. Genetic evidence further underlined the positive correlation between SAG expression in attached leaves and H(2)S. In addition, effects of H(2)S on SAG expression in attached leaves were compromised in the S-nitrosoglutathione reductase-deficient mutant, gsnor1. Taken together, our results suggest that H(2)S suppresses chlorophyll degradation of detached leaves by regulating a dark-dependent reaction, and that this gas positively modulates SAG expression in attached leaves under prolonged darkness in a GSNOR1-dependent manner.