Functional and Evolutionary Characterization of the CONSTANS-like Family in Lilium x formolongi

摘要

Lilium x formolongi is a facultative long-day (LD) plant. Aiming to dissect the molecular regulation of the photoperiodic pathway, largely unknown in ilium, we explored the CONSTANS/FLOWERING LOCUS T (CO/FT) module, a major regulatory factor in the external coincidence model of the photoperiodic flowering pathway in lily. We identified eight CONSTANS-LIKE (COL) family members in Lilium x formolongi, which could be divided into three types, according to their zinc-finger (B-box) protein domains. Type I included only LKOL5, containing two B-box motifs. Type II contained six LKOLs members that had only one B-box motif. Type III contained only LKOL9 that showed a normal B-box and a second divergent B-box motif. Phylogenic analyses revealed that LfCOLS was the closest to Arabidopsis CO. LfCOLS, LfC0L6 and LfCOL9 were up-regulated at the flowering induction stage under LDs, coinciding with an increase in LfFT1 expression. LfCOLS, LfCOL6 and LfCOL9 also showed obvious diurnal expression pattern for 3 d under LDs. However, under short-day (SD) conditions, the expression patterns of LfCOLS, LfCOL6 and LfCOL9 were variable and complex, with regard to the developmental stages and circadian rhythm. LfCOLS, LfCOL6 and LfCOL9 complemented the late flowering phenotype of the co mutant in Arabidopsis. Taken together, the results suggest that LfCOLS, LfC01.6 and LfCOL9 are involved in triggering flowering induction under LDs. LfCOL6 and LfCOL9 belong to types different from functional COL homologs in other plant species, illustrating the variation in phylogeny, evolution and gene function among LfCOL family members.