The repressor FLOWERING LOCUS C (FLC) holds a key position among the genes, which drive Arabidopsis floral transition along the vernalization pathway. The FRIGIDA (FRI) gene activates FLC expression, and the interplay of strong and weak alleles of FLC and FRI in many cases explains the variations in Arabidopsis requirement for cold induction. In annual and biennial life forms of Brassica, the variations in time to flower have been also related to FLC; whereas the place of FRI in the vernalization process has not been sufficiently elucidated. In contrast to Arabidopsis, FRI in Brassica genomes A and C and presumably B is represented by two expressible loci, FRI.a and FRI.b, each of them manifesting genome-specific polymorphisms. FRI.a and FRI.b sequences from diploid species B. rapa (genome A) and B. oleracea (genome C) are conserved (96–99% similarity) in subgenomes A and C of tetraploid species B. carinata (genome BC), B. juncea (genome AB), and B. napus (genome AC). Phylogenetic analysis of FRI sequences in the genus Brassica clearly discerns the lineages A/C and B, while in the family Brassicaceae, two FRI clusters discriminated by such analysis correspond to the lineages I (including the genus Arabidopsis) and II (including the genus Brassica). The origin of two FRI loci is discussed in the context of the Brassicaceae evolution via paleopolyploidy and subsequent genome reorganization.
Russian Journal of Plant Physiology – Springer Journals
Published: Apr 27, 2014
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