Nucleoporin Nup96 promotes plant photomorphogenesis by facilitating phyB photobody formation and HOS1-mediated PIF5 degradation in Arabidopsis

The initiation of light signaling involves the formation of phyB nuclear photobodies (PBs). The nuclear pore complex (NPC) is the sole gate for macromolecule transport between the cytoplasm and nucleus; however, its role in phyB PB formation and light signal transduction remains unclear. Here, we identify Nup96, a nucleoporin in the NPC subcomplex Nup107-160, as a key regulator that promotes plant photomorphogenesis. Nup96 interacts with phyB at the nuclear envelope to facilitate phyB PB formation and enhance phyB activity. Moreover, this interaction promotes phyB-PIF5 association, thereby facilitating PIF5 degradation. Notably, knocking out PIF5 fully rescues the hypocotyl phenotype of nup96-1. Further analyses identify an E3 ligase, HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 1 (HOS1), which interacts with PIF5 to promote its degradation via the 26S proteasome pathway. Collectively, our study elucidates a mechanism by which Nup96 promotes PIF5 degradation by enhancing phyB activity and stabilizing HOS1, thereby ensuring precise light-regulated growth in plants.