Additional targets of the Arabidopsis autonomous pathway members, FCA

A central player in the Arabidopsis floral transition is the floral repressor FLC, the MADS-box transcriptional regulator that inhibits the activity of genes required to switch the meristem from vegetative to floral devel-opment. One of the many pathways that regulate FLC expression is the autonomous promotion pathway composed of FCA, FY, FLD, FPA, FVE, LD, and FLK. Rather than a hierarchical set of activities the auton-omous promotion pathway comprises sub-pathways of genes with different biochemical functions that all share FLC as a target. One sub-pathway involves FCA and FY, which interact to regulate RNA process-ing of FLC. Several of the identified components (FY, FVE, and FLD) are homologous to yeast and mamma-lian proteins with rather generic roles in gene regula-tion. So why do mutations in these genes specifically show a late-flowering phenotype in Arabidopsis? One reason, found during the analysis of fy alleles, is that the mutant alleles identified in flowering screens can be hypomorphic, they still have partial function. A broader role for the autonomous promotion pathway is supported by a microarray analysis which has identified genes mis-regulated in fca mutants, and whose expression is also altered in fy mutants