Hydrogen sulfide promotes flowering in heading Chinese cabbage by S-sulfhydration of BraFLCs
Xiaoli Ma, Liping Zhang, Zhuoya Pei, Linlin Zhang, Zhiqiang Liu, Danmei Liu, Xuefeng Hao, Zhuping Jin, Yanxi Pei
Abstract
Abstract 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 diversified 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 2 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 identified 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 100 μmol L −1 significantly promoted flowering by compensating for insufficient 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.