Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2006
Publication Date: 12/18/2006
Citation: Reeves, P.A., Yuehui, H., Schmitz, R.J., Amasino, R.M., Panella, L.W., Richards, C.M. 2006. Evolutionary Conservation of the Flowering Locus C-Mediated Vernalization Response: Evidence From the Sugar Beet (Beta vulgaris). Genetics 176: 295-307 (May 2007) DOI: 10.1534/genetics.106.069336.
Interpretive Summary: Many plants require a lengthy cold treatment, namely winter, in order to flower. This process is termed "vernalization." The vernalization response in the model organism Arabidopsis thaliana is controlled by the interaction of two genes, FRIGIDA (FRI) and FLOWERING LOCUS C (FLC). Neither gene has been found outside the plant family Brassicaceae, to which Arabidopsis belongs, in spite of numerous efforts to do so. We used phylogenetic analysis of protein sequences "mined" from expressed sequence tag databases to identify FLC-like genes in tomato, poplar, and sugar beet, distant relatives of Arabidopsis. The FLC-like gene in sugar beet, which we named BvFL1, behaves in a manner similar to Arabidopsis FLC during a vernalization treatment: it is a repressor of flowering that is down regulated by cold. We conclude that the fundamental elements of the vernalization response are conserved between Arabidopsis and sugar beet. Based on known flowering plant phylogenetic relationships, we predict that FLC-like genes are present in the majority of dicot species. Conservation of the basic genetic mechanism underlying the vernalization response implies an opportunity to control flowering time, a trait of critical agronomic importance, in most dicot crop species
Technical Abstract: In many plants, exposure to a prolonged period of cold during the winter promotes flowering in the spring, a process termed vernalization. In Arabidopsis thaliana, the vernalization response is controlled by the MADS box gene FLOWERING LOCUS C (FLC). The vernalization response in wheat, a distantly related monocot, involves a distinct genetic mechanism. The extent to which either vernalization mechanism has been conserved during the diversification of flowering plants has not been established. Using phylogenetic analysis, we identified homologs of FLC in species representing the three major eudicot lineages. We show that the sugar beet FLC homolog BvFL1 is, like FLC, a repressor of flowering that is down regulated in response to cold. We predict that cold induced down regulation of an FLC like floral repressor is likely to be a central feature of the vernalization response in at least half of eudicot species.