Components of the Arabidopsis autonomous floral promotion pathway, FCA and FY, are conserved in monocots.

Abstract

The autonomous floral promotion pathway plays a key role in regulating the flowering time of the model dicot Arabidopsis thaliana (L.) Heynh. To investigate whether this pathway is present in monocots, two autonomous pathway components, FCA and FY, were isolated from rice (Oryza sativa L.) and ryegrass (Lolium perenne L.). The predicted FCA proteins (OsFCA and LpFCA) are highly conserved over the RNA-binding and WW protein interaction domains, and the FY proteins (OsFY and LpFY) possess highly conserved WD repeats but a less well conserved C-terminal region containing Pro-Pro-Leu-Pro (PPLP) motifs. In Arabidopsis, FCA limits its own production by promoting the polyadenylation of FCA pre-mRNA within intron 3 to form a truncated transcript called FCA-β. The identification of FCA-β transcripts in rice and ryegrass indicates that equivalent mechanisms occur in monocots. FCA's autoregulation and flowering time functions require FCA to interact with the 3' end-processing factor, FY. The FCA WW domain from Arabidopsis, which is thought to recognise PPLP motifs, interacted with ryegrass FY protein in GST-pulldown assays. Together these results suggest that the FCA and FY genes in monocots have similar functions to the dicot flowering-time genes. The cloning of these genes may provide targets for manipulating the flowering time of monocot species.