Conserved and unique features of pepper FLOWERING LOCUS T-like genes revealed by comparative analysis among solanaceous crops

FLOWERING LOCUS T (FT)-like genes play crucial and antagonistic roles in flowering induction in plants. We analyzed the functional and evolutionary characteristics of pepper FT-like genes. According to their similarity to an FT ortholog of tomato, 10 phosphatidylethanolamine-binding protein family genes were retrieved from the pepper genome. Phylogenetic analysis placed the proteins encoded by six of these genes (CaFT1-CaFT6) into an FT-like clade. Comparative genomic analysis showed that four of pepper FT-like genes (CaFT1, CaFT2, CaFT3, CaFT4) have orthologous counterparts in other three solanaceous crops (tomato, potato, and tobacco). CaFT5, which is unique to pepper, was inferred to have arisen by genomic rearrangement followed by duplication of CaFT2. Interestingly, CaFT6, which has been nominated as a pepper FT ortholog, was located in a genomic region not syntenic to the loci of FT orthologs in other crops and was clustered with two other FT-like genes. This result implies the involvement of a unique evolutionary process in the origin of CaFT6. Pepper FT-like genes were mostly expressed in leaves, and their protein products interacted with FLOWERING LOCUS D. When they were overexpressed in Arabidopsis, flowering was promoted by two genes (CaFT6 and CaFT4) and delayed by two others (CaFT1 and CaFT3). The expressions of CaFT6 and CaFT4 were also negatively related to flowering time in pepper accessions implying that they act as flowering promoter genes. The conserved and unique characteristics of pepper FT-like genes provide insights into the dynamic evolution of FT-like genes and useful information for manipulation of FT-like genes to improve the productivity.