Effect of Photoperiod on the Regulation of Wheat Vernalization Genes VRN1 and VRN2

Dubcovsky, J. (2006) Effect of Photoperiod on the Regulation of Wheat Vernalization Genes VRN1 and VRN2. Plant Molecular Biology , 60 (4). pp. 469-480.

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Wheat is usually classified as a long day (LD) plant because most varieties flower earlier when exposed to longer days. In addition to LD, winter wheats require a long exposure to low temperatures (vernalization) to become competent for flowering. Here we show that in some genotypes this vernalization requirement can be replaced by interrupting the LD treatment by 6 weeks of short day (SD), and that this replacement is associated with the SD down-regulation of the VRN2 flowering repressor. In addition, we found that SD down-regulation of VRN2 at room temperature is not followed by the up-regulation of the meristem identity gene VRN1 until plants are transferred to LD. This result contrasts with the VRN1 up-regulation observed after the VRN2 down-regulation by vernalization, suggesting the existence of a second VRN1 repressor. Analysis of natural VRN1 mutants indicated that a CArG-box located in the VRN1 promoter is the most likely regulatory site for the interaction with this second repressor. Up-regulation of VRN1 under SD in accessions carrying mutations in the CArG-box resulted in an earlier initiation of spike development, compared to other genotypes. However, even the genotypes with CArG box mutations required LD for a normal and timely spike development. The SD acceleration of flowering was observed in photoperiod sensitive winter varieties. Since vernalization requirement and photoperiod sensitivity are ancestral traits in Triticeae species we suggest that wheat was initially a SD–LD plant and that strong selection pressures during domestication and breeding resulted in the modification of this dual regulation. The down-regulation of the VRN2 repressor by SD is likely part of the mechanism associated with the SD–LD regulation of flowering in photoperiod sensitive winter wheat.

Item Type: Article
Additional Information: This project was supported by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service, grant number 2003–00703 and 2003–00929. The authors thank Lenka Valarikova for excellent technical assistance and Marı´a Laura Appendino for her contribution of the G3116 flowering data.
Author Affiliation: 1.University of California Department of Plant Sciences, Mail Stop 1 One Shields Avenue Davis CA 95616-8780 USA One Shields Avenue Davis CA 95616-8780 USA
Subjects: Crop Improvement
Divisions: Other Crops
Depositing User: Mr. SanatKumar Behera
Date Deposited: 09 Mar 2012 12:02
Last Modified: 09 Mar 2012 12:03
Official URL: http://dx.doi.org/10.1007/s11103-005-4814-2
URI: http://eprints.icrisat.ac.in/id/eprint/3722

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