Phosphorus Availability Modulates Flowering Time Through Subcellular Reprogramming of bGLU25 and GRP7 in Flowering Plants

The transition from vegetative to reproductive growth is vital for plant fitness and crop yield and is strongly influenced by nutrient availability. While nitrogen deficiency accelerates flowering, phosphorus (P) limitation delays it. However, the molecular basis for how P availability regulates flowering time remains unclear. Here, through genome-wide association mapping in Arabidopsis, we uncover genetic variation in {beta}-GLUCOSIDASE 25 (bGLU25) that modulates flowering under P-limited conditions. In P-sufficient environments, bGLU25 localizes to the endoplasmic reticulum. Under P limitation, however, bGLU25 translocates to the cytosol, a process mediated by P-regulated SERINE CARBOXY PEPTIDASE 50 (SCP50). In the cytosol, bGLU25 binds to JACALIN-LECTIN LIKE1 (AtJAC1), preventing the nuclear translocation of the Flowering Locus C (FLC) regulator GLYCINE-RICH RNA-BINDING PROTEIN 7 (GRP7). This cytosolic sequestration of GRP7 under P-deprivation elevates FLC expression, delaying flowering. Moreover, in the monocot rice, the homologs of bGLU25 also modulate flowering responses to P availability, indicating a conserved role for bGLU25 across flowering plants. Our findings provide a molecular framework for breeding strategies aimed at optimizing flowering time in response to P levels.