Journal of Heredity Advance Access originally published online on February 27, 2009
Journal of Heredity 2009 100(3):355-364; doi:10.1093/jhered/esp002
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Original Articles |
The CArG-Box Located Upstream from the Transcriptional Start of Wheat Vernalization Gene VRN1 Is Not Necessary for the Vernalization Response
From the Instituto de Recursos Biológicos, INTA, Villa Udaondo, (1686) Hurlingham, Buenos Aires, Argentina (Pidal and Tranquilli); the Department of Plant Sciences, University of California, Davis, CA (Fu and Dubcovsky); and the Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK (Yan and Zhang). D. Fu is now at the National Key Laboratory of Crop Biology, College of Agronomy, Shandong Agricultural University, Tai'an, Shandong, China
Address correspondence to J. Dubcovsky at the address above, or e-mail: jdubcovsky{at}ucdavis.edu.
In diploid wheat (Triticum monococcum), and likely in other Triticeae species, the VRN1 gene is essential for the initiation of the reproductive phase, and therefore, a detailed characterization of its regulatory regions is required to understand this process. A CArG-box (MADS-box–binding site) identified in the VRN1 promoter upstream from the transcription initiation site has been proposed as a critical regulatory element for the vernalization response. This hypothesis was supported by the genetic linkage between CArG-box natural deletions and dominant Vrn1 alleles for spring growth habit and by physical interactions with VRT2, a MADS-box protein proposed as a putative flowering repressor regulated by vernalization. Here, we describe a T. monococcum accession with a strong vernalization requirement and a 48-bp deletion encompassing the CArG-box in the VRN1 promoter. Genetic analyses of 2 segregating populations confirmed that this VRN1 allele is completely linked with a strong winter growth habit (vrn-Am1b). Transcript levels of the VRN1 allele with the 48-bp deletion were very low in unvernalized plants and increased during vernalization to levels similar to those detected in other wild-type vrn-Am1 alleles. Taken together, these results indicate that the CArG-box found upstream of the VRN1 transcription initiation site is not essential for the vernalization response.
Key Words: CArG-box • flowering • regulatory regions • Triticum monococcum • vernalization • wheat
Corresponding Editor: J. Perry Gustafson
Received July 12, 2008
Revised January 6, 2009
Accepted January 16, 2009