The wheat and barley vernalization gene VRN3 is an orthologue of FT

doi:10.1073/pnas.0607142103

The wheat and barley vernalization gene VRN3 is an orthologue of FT

*Department of Plant Sciences, University of California, Davis, CA 95616;
^‡U.S. Department of Agriculture–Agricultural Research Service, Western Regional Research Center, Albany, CA 94710; and
^¶Research Institute for Bioresources, Okayama University, Kurashiki 710-0046, Japan

Edited by Richard M. Amasino, University of Wisconsin, Madison, WI, and approved October 30, 2006 (received for review August 16, 2006)

Abstract

Winter wheat and barley varieties require an extended exposure to low temperatures to accelerate flowering (vernalization), whereas spring varieties do not have this requirement. In this study, we show that in these species, the vernalization gene VRN3 is linked completely to a gene similar to Arabidopsis FLOWERING LOCUS T (FT). FT induction in the leaves results in a transmissible signal that promotes flowering. Transcript levels of the barley and wheat orthologues, designated as HvFT and TaFT, respectively, are significantly higher in plants homozygous for the dominant Vrn3 alleles (early flowering) than in plants homozygous for the recessive vrn3 alleles (late flowering). In wheat, the dominant Vrn3 allele is associated with the insertion of a retroelement in the TaFT promoter, whereas in barley, mutations in the HvFT first intron differentiate plants with dominant and recessive VRN3 alleles. Winter wheat plants transformed with the TaFT allele carrying the promoter retroelement insertion flowered significantly earlier than nontransgenic plants, supporting the identity between TaFT and VRN-B3. Statistical analyses of flowering times confirmed the presence of significant interactions between vernalization and FT allelic classes in both wheat and barley (P < 0.0001). These interactions were supported further by the observed up-regulation of HvFT transcript levels by vernalization in barley winter plants (P = 0.002). These results confirmed that the wheat and barley FT genes are responsible for natural allelic variation in vernalization requirement, providing additional sources of adaptive diversity to these economically important crops.

Footnotes

^‖To whom correspondence should be addressed. E-mail: jdubcovsky{at}ucdavis.edu
Author contributions: L.Y., D.F., and C.L. contributed equally to this work; L.Y. and J.D. designed research; L.Y., D.F., C.L., A.B., G.T., M.B., and A.S. performed research; S.Y. contributed new reagents/analytic tools; L.Y., D.F., C.L., A.B., G.T., M.B., A.S., M.V., and J.D. analyzed data; and J.D. wrote the paper.
↵ ^†Present address: Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK 74078.
↵ ^§Present address: Instituto de Recursos Biológicos, Instituto Nacional de Tecnología, Agropecuaria, Villa Udaondo, 1712 Castelar, Buenos Aires, Argentina.
The authors declare no conflict of interest.
This article is a PNAS direct submission.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. DQ890162, DQ890163, DQ890165, DQ898515–DQ898519, DQ899784, and DQ900685–DQ900687).
This article contains supporting information online at www.pnas.org/cgi/content/full/0607142103/DC1.
↵**Throughout this study flowering time refers to the time of complete emergence of the spike from the leaf sheath, which is usually referred by cereal scientists as heading time.
Abbreviations:

LD,

long day;

QTL,

quantitative trait loci;

RFLP,

restriction fragment length polymorphism;

RSL,

recombinant substitution line;

SD,

short day.