Analysis of PEBP Genes in Saffron Identifies a Flowering Locus T Homologue Involved in Flowering Regulation

Flowering determines the yield of saffron, whereas synchronized sprouting determines plant fitness; thus, their regulation is of utmost importance. In saffron, corm sprouting is marked with the emergence of flowers and leaves simultaneously. PEBP genes have a conserved role in regulating flowering and vegetative growth in plants, but their role in saffron is confined due to the non-availability of genomic resources. In the present study, we isolated their homologues in saffron and examined their alleged role in promoting flowering. Here we report that at least 6 FTs (FLOWERING LOCUS T), 2 TFL1s (TERMINAL FLOWER 1), and 2 MFTs (MOTHER OF FT AND TFL1) genes are present in saffron. The sequence analysis suggests they possess a conserved structural genetic organization with other plant species gene members. Interestingly, two FT genes (CsatFT4 and CsatFT6) showed the presence of characteristic amino acids of TFL-like genes but were aligned in FT genes clade. Phylogenetic analysis divided them into FT-like, TFL1-like, and MFT-like clades. The expression of identified genes varied among different tissues. The spatial and temporal expressions during sprouting suggest that they might have different functions. Tissue and organ-specific expression profiling suggest that CsatFT3 might act locally in apical buds to promote flowering, while CsatFT1 and 2 are involved in promoting vegetative growth. Antagonistically, CsatTFL1-1 and CsatTFL1-2 might regulate vegetative growth and flowering, respectively. Additionally, comparative expression profiling between flowering competent (big) vs non-competent (small) corms affirm the specific role of CsatFT3 as a plausible flowering regulator.