Control of Arabidopsis flowering: the chill before the bloom.

The timing of the floral transition has significant consequences for reproductive success in plants. Plants gauge both environmental and endogenous signals before switching to reproductive development. Many temperate species only flower after they have experienced a prolonged period of cold, a process known as vernalization, which aligns flowering with the favourable conditions of spring. Considerable progress has been made in understanding the molecular basis of vernalization in Arabidopsis. A central player in this process is FLC, which blocks flowering by inhibiting genes required to switch the meristem from vegetative to floral development. Recent data shows that many regulators of FLC alter chromatin structure or are involved in RNA processing.

FY is an RNA 3' end-processing factor that interacts with FCA to control the Arabidopsis floral transition

The nuclear RNA binding protein, FCA, promotes Arabidopsis reproductive development. FCA contains a WW protein interaction domain that is essential for FCA function. We have identified FY as a protein partner for this domain. FY belongs to a highly conserved group of eukaryotic proteins represented in Saccharomyces cerevisiae by the RNA 3' end-processing factor, Pfs2p. FY regulates RNA 3' end processing in Arabidopsis as evidenced through its role in FCA regulation. FCA expression is autoregulated through the use of different polyadenylation sites within the FCA pre-mRNA, and the FCA/FY interaction is required for efficient selection of the promoter-proximal polyadenylation site. The FCA/FY interaction is also required for the downregulation of the floral repressor FLC. We propose that FCA controls 3' end formation of specific transcripts and that in higher eukaryotes, proteins homologous to FY may have evolved as sites of association for regulators of RNA 3' end processing.