The FT/TFL1 Regulatory Module: A Synthesis of Gene Duplication, Functional Divergence, and Environmental Modulation Across Plant Lineages

The FLOWERING LOCUS T/TERMINAL FLOWER 1 (FT/TFL1) gene family, a key branch of the phosphatidylethanolamine-binding protein (PEBP) superfamily, is widely recognised as a central regulatory module controlling flowering time and inflorescence architecture in plants. Although FT/TFL1 members share highly conserved structural features, they exhibit remarkable functional divergence. The FT generally promotes floral induction, whereas TFL1 delays or represses it, forming an antagonistic regulatory balance. However, increasing evidence from comparative genomics and molecular studies suggests that the classical 'FT activator/TFL1 repressor' paradigm cannot adequately account for the complex behaviours of expanded gene families across diverse species, tissue types, and environmental conditions. In this review, FT/TFL1 copy-number variation and expansion patterns during plant evolution are synthesised, mechanisms of functional diversification are summarised, and insights from protein interaction rewiring and environmental signal integration are integrated. A unified framework for understanding the evolutionary and environmental shaping of FT/TFL1 is provided, offering theoretical guidance for future studies on reproductive development, adaptive evolution, and applied manipulation of flowering traits.