A new Arabidopsis gene, FLK, encodes an RNA binding protein with K homology motifs and regulates flowering time via FLOWERING LOCUS C.

Posttranscriptional RNA metabolism plays versatile roles in the regulation of gene expression during eukaryotic growth and development. It is mediated by a group of RNA binding proteins with distinct conserved motifs. In this study, an Arabidopsis (Arabidopsis thaliana) gene, designated FLK, was identified and shown to encode a putative RNA binding protein with K homology motifs. A mutant in which FLK was inactivated by T-DNA insertion exhibited a severe late flowering phenotype both in long and short days. The late flowering phenotype was reversed by gibberellin and vernalization treatments. The FLOWERING LOCUS C (FLC) transcription was greatly upregulated, whereas those of FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 decreased in the mutant. These observations demonstrate that FLK regulates the autonomous flowering pathway via FLC. It is now evident that a battery of different RNA binding proteins are involved in the posttranscriptional regulation of flowering time in Arabidopsis.