Regulation of FLC nuclear import by coordinated action of the NUP62‐subcomplex and importin β SAD2

Abstract Flowering locus C (FLC) is a central transcriptional repressor that controls flowering time. However, how FLC is imported into the nucleus is unknown. Here, we report that Arabidopsis nucleoporins 62 (NUP62), NUP58, and NUP54 composed NUP62‐subcomplex modulates FLC nuclear import during floral transition in an importin α‐independent manner, via direct interaction. NUP62 recruits FLC to the cytoplasmic filaments and imports it into the nucleus through the NUP62‐subcomplex composed central channel. Importin β supersensitive to ABA and drought 2 (SAD2), a carrier protein, is critical for FLC nuclear import and flower transition, which facilitates FLC import into the nucleus mainly through the NUP62‐subcomplex. Proteomics, RNA‐seq, and cell biological analyses indicate that the NUP62‐subcomplex mainly mediates the nuclear import of cargos with unconventional nuclear localization sequences (NLSs), such as FLC. Our findings illustrate the mechanisms of the NUP62‐subcomplex and SAD2 on FLC nuclear import process and floral transition, and provide insights into the role of NUP62‐subcomplex and SAD2 in protein nucleocytoplasmic transport in plants.