Germplasm screening and genome-wide PEBP profiling identify key regulators of photoperiod-insensitive flowering in winged bean (Psophocarpus tetragonolobus L)

Winged bean (Psophocarpus tetragonolobus L.) is a nutritionally rich underutilized tropical legume. It requires short-day (SD) conditions for flowering, which limits its cultivation across seasons and regions. In this study, 81 winged bean accessions were evaluated over three years under contrasting natural photoperiods, identifying five genotypes capable of flowering under both short- and long-day conditions. However, only one accession (IIAB-PIS1) achieved full reproductive development under long-day (LD) conditions. To understand the molecular basis of this trait, we conducted a genome-wide identification and analysis of the phosphatidylethanolamine-binding protein (PEBP) genes, which are key regulators of flowering-time pathways. Ten PEBP genes were identified and classified into FT-like, TFL1/CEN-like, and MFT-like groups, each of which displayed conserved domain structures and features. Divergence time analysis indicated recent diversification within subfamilies. Expression profiling under LD conditions showed that FT2 may be the potential candidate gene for florigen production in both photoperiod-sensitive and -insensitive genotypes. In contrast, differential expression of FT1, FT4, TFL1, and CEN2 suggested genotype-specific regulation of floral transition pathways. The discovery of a truly photo-insensitive genotype, along with the identification of key regulatory PEBP genes, offers valuable resources for developing high-yielding, photoperiod-insensitive winged bean cultivars.