Minisymposium 11: Reproductive Development

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Abs # M1103: TaVRT-2 is the major flowering repressor that regulates the expression of the wheat vernalization gene VRN-1.

Presenter:	Adam, Helene       Contact Presenter
Authors	Adam, Helene  (A)   Kane, Ndjido  (A)   Agharbaoui, Zahra  (A)   Diallo, Amadou  (A)   Tominaga, Yoko  (A)   Sarhan, Fathey  (A)
Affiliations:	(A): Univ. du Quebec a Montreal

Vernalization and photoperiod are two major environmental cues that regulate the flowering time. Vernalization is the promotion of flowering by exposure to prolonged period of cold. This promotion of flowering is due to cold and photoperiod mediated suppression of several repressors. These repressors have been identified and characterized in the model plant system Arabidopsis. However, very little is known in temperate cereals. The recent discovery of three vernalization genes, TaVRT-1 (VRN-1),VRN-2 and TaVRT-2, provides the tools to decipher the complexity of the molecular basis of vernalization in cereals. The spatio-temporal expression of these genes, determined by in situ hybridization, revealed that these genes are expressed in the same tissues (apical meristem and young leaf) in response to vernalization. Protein-DNA interactions and transactivation experiments revealed that TaVRT-2 acts up-stream of VRN-1 and represses its promoter activity. On the other hand, VRN-2 does not interact with the VRN-1 promoter and has no repression effect in the transactivation system used in our experiment. However, the VRN-2/TaVRT-2 complex enhances the repression of VRN-1 promoter. We further show that over-expression of TaVRT2 in Arabidopsis plants delays flowering by more than ten days. These data support our hypothesis that TaVRT-2 is a major repressor of flowering in cereals and other plants. The function of this protein and its role in regulating VRN-1 and the transition from vegetative to reproductive phase will be discussed.