A common strategy for plants to avoid entering the reproductive phase immediately before or within the non-permissive cold period of the northern and southern latitudes is the necessity for vernalization. This means that they have to pass through a long period (months) with cold temperatures before they undergo floral transition.
The perception of cold temperature and the flowering response can be separated in time, often for several weeks and this molecular memory seems to have an epigenetic basis as the vernalized state is passed to daughter cells through mitosis. Breeding for vernalization requirement has been an important trait in many crop species with the generation of winter varieties extending the geographical range of where the crop can be grown.
The molecular analysis of floral transition in Arabidopsis thaliana revealed the essential role of the floral inhibitor gene FLC. Cold treatment of plants sensitive for vernalization leads to a down regulation of FLC transcription. Screens for mutants that are defective in the vernalization response resulted in the isolation of two genes, VRN1 and VRN2, that are essential to maintain the transcriptional repression of FLC induced by cold treatment. The results of molecular analyses argue for a function of VRN1 and VRN2 in DNA remodelling.
The objective of this proposal will be the molecular identification and characterization of VRN5, a gene that is, similar to VRN1 and VRN2, involved in the maintenance of FLC repression. The identification of a new factor will help to complete the picture of this epigenetic stabilization of a cold-induced response mechanism.
By in vivo co-immunoprecipitation and Yeast-Two-Hybrid experiments, interacting proteins will be isolated and the VRN5 function will be integrated in the process of FLC down regulation. In addition, chromatin immunoprecipitation assays will be used to establish whether VRN5 directly interacts with the FLC genomic region in vivo.
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