Importinβ4 mediates nuclear import of grf-interacting factors to control ovule development in arabidopsis

Abstract

Ovule development is critical for seed development and plant reproduction. Multiple transcription factors (TFs) have been reported to mediate ovule development. However, it is not clear which intracellular components regulate these TFs during ovule development. After their synthesis, TFs are transported into the nucleus a process regulated by karyopherins commonly known as importin alpha and b. Around half of Arabidopsis (Arabidopsis thaliana) importin b-coding genes have been functionally characterized but only two with specific cargos have been identified. We report here that Arabidopsis IMPORTINβ4 (IMβ4) regulates ovule development through nucleocytoplasmic transport of transcriptional coactivator growth regulating factors–interacting factors (GIFs). Mutations in IMβ4 impaired ovule development by affecting integument growth. imβ4 mutants were also defective in embryo sac development, leading to partial female sterility. IMβ4 directly interacts with GIFs and is critical for the nucleocytoplasmic transport of GIF1. Finally, functional loss of GIFs resulted in ovule defects similar to those in imβ4 mutants, whereas enhanced expression of GIF1 partially restored the fertility of imβ4. The results presented here uncover a novel genetic pathway regulating ovule development and reveal the upstream regulator of GIFs.