Genome-wide characterization of the PHY gene family in octoploid strawberry reveals the critical role of FxaPHY15 in far-red light signaling and fruit ripening

Phytochrome (PHY) genes are crucial for the appropriate growth, development, and environmental adaptation of plants. Nevertheless, the composition of the PHY gene family in octoploid strawberry and its underlying light - signaling mechanisms remain unclear. This study identified 18 FxaPHY members distributed across the subgenomes, categorized into four distinct evolutionary clades. Notably, FxaPHY15 emerged as a key candidate due to its profound responsiveness to far-red (FR) light and its specific transcriptional peak during the fruit turning-color transition. Subcellular assays and protein interaction networks further confirmed that FxaPHY15 localizes to the nucleus and forms a high-confidence regulatory module with PIF3 (phytochrome-interacting factors 3), potentially orchestrating the transition from vegetative growth to fruit maturation. In summary, this study provides the first comprehensive overview of the PHY gene family in octoploid strawberry and establishes FxaPHY15 as a potential important candidate gene mediating far-red light responses and fruit development, laying the foundation for light signal transduction research in strawberry.