Alternative splicing and expression analysis of OsFCA (FCA in Oryza sativa L.), a gene homologous to FCA in Arabidopsis

A subtracted cDNAs library was constructed using rice (Oryza sativa L.) calli cDNA as driver and differentiating calli cDNA as tester. A novel gene homologous with FCA in Arabidopsis was cloned from rice by screening the SSH (suppression subtractive hybridization) library followed by RACE. Four alternative transcripts of OsFCA were cloned from the leaves of rice, and designated as OsFCA-1, OsFCA-2, OsFCA-3 and OsFCA-4 respectively. OsFCA-1 was homologous to FCA- gamma of Arabidopsis and contained several conserved domains (two RNA Recognition Motifs and one WW-domain). OsFCA-2 was 102 bp shorter than OsFCA-1 which caused the WW-domain deletion. The proteins encoded by OsFCA-3 and OsFCA-4 were 101 amino acids shorter than OsFCA-1 at the N-terminal which is a glycine-rich region. The fluorescence quantitative PCR analysis showed that the mRNA of OsFCA-1 is the most abundant in the four splicing variants of rice FCA, and its expression level is much higher in differentiating calli than in calli. The expression of OsFCA-1 is steady in the leaves of three different stage, but up-regulated in young spikelet of primary branch-differentiating stage and down-regulated in young spikelet of pistil and stamen-differentiating stage.