A gain‐of‐function mutation at the C‐terminus of FT‐D1 promotes heading by interacting with 14‐3‐3A and FDL6 in wheat

Summary Vernalization and photoperiod pathways converging at FT1 control the transition to flowering in wheat. Here, we identified a gain‐of‐function mutation in FT‐D1 that results in earlier heading date (HD), and shorter plant height and spike length in the gamma ray‐induced eh1 wheat mutant. Knockout of the wild‐type and overexpression of the mutated FT‐D1 indicate that both alleles are functional to affect HD and plant height. Protein interaction assays demonstrated that the frameshift mutation in FT‐D1 eh1 exon 3 led to gain‐of‐function interactions with 14‐3‐3A and FDL6, thereby enabling the formation of florigen activation complex (FAC) and consequently activating a flowering‐related transcriptomic programme. This mutation did not affect FT‐D1 eh1 interactions with TaNaKR5 or TaFTIP7, both of which could modulate HD, potentially via mediating FT‐D1 translocation to the shoot apical meristem. Furthermore, the ‘Segment B’ external loop is essential for FT‐D1 interaction with FDL6, while residue Y85 is required for interactions with TaNaKR5 and TaFTIP7. Finally, the flowering regulatory hub gene, ELF5 , was identified as the FT‐D1 regulatory target. This study illustrates FT‐D1 function in determining wheat HD with a suite of interaction partners and provides genetic resources for tuning HD in elite wheat lines.