Functional Differentiation Of BrFLCs In Chinese Cabbage And Flowering Regulation Of Hydrogen Sulfide

Flowering is an important stage of plant growth.The study of flowering time regulation has very important significance and application value in plant breeding and agricultural production.There are four main pathways to affect flowering time in Arabidopsis thaliana.FLOWERING LOCUS C?FLC?is a pivotal factor in flowering regulation.Chinese cabbage?Bassica rapa L ssp.Pekinensis?is an important Brassica vegetable crop,the breeding and spring cultivation have attracted much attention.And its genome has a clear linear relationship with that in Arabidopsis thaliana.The functional redundancy or differentiation of four FLC homologs in Chinese cabbage still remains to be determined.Hydrogen sulfide?H₂S?,a gas signal molecule,has rapid progress in the field of plants and possesses a variety of roles in plants,including growth and development regulation and abiotic stress response.In the current study,we explored the spatiotemporal expression patterns of Br FLCs in Chinese cabbage and determined the functional differentiation of FLC homologs,but also analyze the effect of H₂S on their expression.And the spatiotemporal expression patterns of Br FLC homologs under H₂S treatment was obtained.The main results in this study are as follows:1.The four FLC homologs showed different temporal and spatial specific expression patterns.The expression patterns of Br FLC1,2 and 3were consistent with that of At FLC,and the expression was highest at the start of the experiment,but then decreased rapidly after 20 D of treatment.Whereas there were no significant changes in the expression of Br FLC5.Br FLC1 was expressed almost exclusively in leaves and cotyledons,whereas Br FLC2 was detected in various development stages.There was not noticeable change in Br FLC3 and 5 in the tissues examined,although Br FLC3 always showed the highest expression.Different expression patternsof Br FLCs may be related to their functional differentiation.2.Exogenous H₂S promoted the flowering of Chinese cabbage significantly.Overall,Br FLC expression was slightly downregulated following exogenous H₂S treatment.Br FLC2 decreased most obviously,with decreases in the leaves being most noticeable.Thus,H₂S appears to be able regulate the downstream genes of Br FLCs to varying degrees and the variation in the expression patterns of downstream genes could be the result of the level of S-sulfhydration of H₂S and the functional diversity of the Br FLCs.3.The flc3 Br FLCs-HA mutants was obtained by genetic transformation.Using Ch IP-q PCR,we found Br FLCs could be combined with the downstream genes of At FLC to varying degrees.Br FLC1 strongly interacted with FT;Br FLC2 interacted with FT and SOC1;Br FLC3 interacted with flowering and vegetative growth genes;Br FLC5 and SPL15 had stronger effects.The function of Br FLCs and its different temporal and spatial specific expression patterns echoed each other,which proved that Br FLCs had functional differentiation.In summary,FLC homologs showed different temporal and spatial specific expression patterns,and Br FLC3 had the highest expression.Exogenous H₂S promoted the flowering of Chinese cabbage significantly.Br FLC2 decreased most obviously following exogenous H₂S treatment,with decreases in the leaves being most noticeable.All of four Br FLC genes could restore the early flowering phenotype of Arabidopsis flc3 mutant.Among them,only Br FLC5 could not recover all the early flowering phenotype of flc3.