Regulation of FLC nuclear import by coordinated action of the NUP62-subcomplex and importin & beta; SAD2

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 & alpha;-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 & beta; 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.

Automated summary

The nuclear import of FLC during floral transition is mediated by the NUP62-subcomplex, which includes nucleoporins NUP62, NUP58, and NUP54, in an importin & alpha;-independent manner. The carrier protein SAD2 is critical for FLC nuclear import and flower transition mainly through the NUP62-subcomplex, which mediates the import of cargos with unconventional NLSs, including FLC.