ASPB President's Symposium
Dubcovsky, Jorge .
The vernalization pathway in temperate cereals.
Wheat and barley varieties with a winter growth habit require an extended exposure to low temperatures to accelerate flowering (vernalization). The recent cloning of the main vernalization genes from these temperate cereals showed that the final steps of the vernalization pathways from cereals and Arabidopsis are different. FRI and FLC, the central genes in the Arabidopsis vernalization pathway, are absent in the temperate cereals, whereas VRN2, the central flowering repressor in the temperate cereals, is absent in Arabidopsis. VRN2 is down-regulated by both vernalization and short days (SD) explaining the ability of SD days (followed by LD), to eliminate the vernalization requirement in most temperate grasses. VRN2 negatively regulates VRN3 and VRN1, the main dominant genes for spring growth habit. VRN3 is similar to Arabidopsis FT and induces flowering under LD. VRN1 is similar to the Arabidopsis meristem identity gene AP1, and is positively regulated by VRN3. The increase of VRN1 transcripts is followed by the down-regulation of VRN2, likely as part of a feedback regulatory loop. Unvernalized winter plants grown under LD exhibit high levels of VRN2 transcripts and low levels of VRN1 and VRN3. Vernalization under LD results in the down regulation of VRN2, and the up-regulation of VRN3 and VRN1. Under SD, all three genes show low transcript levels, but a rapid up-regulation of VRN1 and VRN3 is observed when plants are transferred from SD to LD. The absence of a functional VRN2 repressor eliminates the effect of VRN1 and VRN3 allelic differences on flowering time, whereas mutations in regulatory region of the dominant VRNI or VRN3 alleles preclude their recognition by the VRN2 mediated repression. This model explains the known epistatic interactions among these genes.
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Dubcovsky web page
1 - University of California, Plant Sciences, One Shields Av., Davis, CA, 95616, USA
Presentation Type: ASPB Major Symposium
Location: International Ballroom North/Hilton
Date: Wednesday, July 11th, 2007
Time: 3:50 PM