In plants, the switch to flowering is a key developmental transition that is promoted by limiting the accumulation of the floral repressor FLC. In the autonomous flowering pathway, which is regulated by endogenous cues such as plant size, FLC accumulation is regulated by the interaction between FCA, a plant-specific RNA-binding protein, and FY, a conserved polyadenylation factor. Henderson and co-workers now reveal that FY also plays essential roles in plant development (see ). By examining a series of fy mutations in Arabidopsis, the researchers have discovered that mutations in the N terminus of FY cause embryonic lethality. By contrast, mutations in FY's C-terminal domain (through which it interacts with FCA) and in its WD repeats affect only flowering time. Thus, the researchers conclude, FY mediates both constitutive and regulated RNA 3′-end processing.
