Cloning and characterization of barley caryopsis FCA

The RNA binding protein, flowering control locus A, (FCA) regulates flowering in rice and Arabidopsis. FCA interacts with FY to auto-regulate its own transcripts as well as to control flowering by downregulating flowering locus C (FLC). We report the cloning and characterization of the gamma (γ) isoform of FCA from barley (Hordeum vulgare cv. McLeod). The deduced protein contained two RNA recognition motifs (RRMs), a glycine-rich region at the N-terminal end, a polyglutamine region immediately downstream of a WW domain. Barley FCA had greater protein sequence homology to wheat and rice FCA than to its Arabidopsis homolog. In developing barley embryos, FCA transcripts could be detected from 2 days after pollination (DAP) up to 40 DAP. FCA transcript levels in mature barley embryo were more abundant in non-germinated than in germinated seeds, with the levels declining as germination progressed. ABA inhibition of germination inhibited the decline of barley embryo FCA. Transient co-expression of FCA or a truncated FCA (lacking RRM) with maize VP1 promoter or wheat Em gene promoter in barley aleurone protoplasts led to increased VP1 and Em gene promoter activity. Barley FCA or truncated FCA localized in the nucleus suggested its role in gene regulation.