Alternative splicing and the control of flowering time.

The fca mutant of Arabidopsis is one of numerous late-flowering mutants in the autonomous, or constitutive, floral promotion pathway (Koornneef et al., 1991, 1998). The autonomous pathway acts independently of the photoperiod pathway and intersects with the vernalization response pathway in the control of flowering. The FCA gene encodes a novel protein that contains RNA binding domains and a putative protein– protein interaction domain (Macknight et al., 1997). In this issue of The Plant Cell , Macknight et al. (pages 877– 888) show that alternative splicing of the FCA transcript has functional significance related to its role in the promotion of the floral transition (Figure 1).