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

The initiation of light signaling involves the formation of phyB nuclear photobodies (PBs). Nuclear Pore Complex (NPC) is the sole gate for movement of macromolecules between cytoplasm and nucleus, however, its role in phyB PBs formation and light signal transduction remains ambiguous. Here, we identify Nup96, a nucleoporin in the NPC subcomplex Nup107-160, as a key player in promoting plant photomorphogenesis. Our findings demonstrate that Nup96 interacts with phyB on the nuclear envelope to facilitate phyB PBs formation and increase phyB activity. Moreover, this interaction promotes phyB and PIF5 interaction to facilitate PIF5 degradation, knocking out PIF5 fully recovers nup96-1 hypocotyl phenotype. Additional studies identify an E3 ligase HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 1 (HOS1), which interacts with PIF5 to promote PIF5 degradation via 26S proteasome pathway. Collectively, our study elucidates the mechanism that Nup96 promotes PIF5 degradation via increasing phyB activity and stabilizing HOS1, thereby ensuring precise light-regulated growth in plants.