Abstract
The AP1/FUL-like family plays key roles in floral development and flowering time in plants, influencing plant architecture and grain yield. However, the functions of AP1/FUL-like family members in sorghum (Sorghum bicolor) have yet to be fully elucidated. In this study, we used CRISPR/Cas9 to characterise SbFUL1 in sorghum through comprehensive phenotypic and molecular analyses. The Sbful1 mutants exhibited significant delays in flowering time. Quantitative phenotypic assays revealed changes in seed morphology and inflorescence architecture, which are consistent with previously reported functions of FUL1 in other plant species. Notably, the mutants displayed novel pleiotropic effects on stem morphology not previously associated with FUL1 genes, including changes in stem structure and integrity. DAP-seq analysis identified potential SbFUL1 binding sites in genes involved in pectin biosynthesis and cell wall remodelling pathways, providing a putative molecular mechanism for the observed phenotypes. These findings confirm the conserved roles of FUL1 in regulating flowering time and floral development sorghum while also revealing broader pleiotropic effects than previously recognised. This study demonstrates the value of holistic phenotypic approaches for gene characterisation and highlights opportunities for crop improvement through harnessing floral regulatory genes with expanded functional roles.