Hydrogen sulfide promotes flowering in heading Chinese cabbage by S-sulfhydration of BraFLCs

Heading Chinese cabbage(Brassica rapa L.syn.B.campestris L.ssp.chinensis Makino var.pekinensis(Rupr.)J.Cao et Sh.Cao)is a cruciferous Brassica vegetable that has a triplicate genome,owing to an ancient genome duplication event.It is unclear whether the duplicated homologs have conserved or diversi fied functions.Hydrogen sulfide(H_(2)S)is a plant gasotransmitter that plays important physiological roles in growth,development,and responses to environmental stresses.The modification of cysteines through S-sulfhydration is an important mechanism of H_(2)S,which regulates protein functions.H?S promotes flowering in Arabidopsis and heading Chinese cabbage.Here we investigated the molecular mechanisms of H_(2)S used to promote flowering in the latter.Four,five,and four BraFLC,BraSOC I,and BraFT homologs were identi fi ed in heading Chinese cabbage.Different BraFLC proteins were bound to different CArG boxes in the promoter regions of the BraSOC I and BraFT homologs,producing different binding patterns.Thus,there may be functionally diverse BraFLC homologs in heading Chinese cabbage.Exogenous H_(2)S at 100μmol L^(-1) significantly promoted flowering by compensating for insuf fi cient vernalization.BraFLC 1 and BraFLC_(3) underwent S-sulfhydration by H_(2)S,after which their abilities to bind most BraSOC I or BraFT promoter probes weakened or even disappeared.These changes in binding ability were consistent with the expression pattern of the BraFT and BraSOC I homologs in seedlings treated with H_(2)S.These results indicated that H_(2)S signaling regulates flowering time.In summary,H_(2)S signaling promoted plant flowering by weakening or eliminating the binding abilities of BraFLCs to downstream promoters through S-sulfhydration.