Molecular analysis of FRIGIDA, a major determinant of natural variation inArabidopsis flowering time

Vernalization, the acceleration of flowering by a long period of cold tempe rature, ensures that many plants overwinter vegetatively and flower in spri ng. In Arabidopsis, allelic variation at the FRIGIDA (FRI) locus is a major determinant of natural variation in flowering time. Dominant alleles of FR I confer Late flowering, which is reversed to earliness by vernalization. W e cloned FRI and analyzed the molecular basis of the allelic variation, Mos t of the early-flowering ecotypes analyzed carry FRI alleles containing one of two different deletions that disrupt the open reading frame. Loss-of-fu nction mutations at FRI have thus provided the basis for the evolution of m any early-flowering ecotypes.