Molecular characterization of the major wheat domestication gene Q

Genetics. 2006 Jan;172(1):547-55. doi: 10.1534/genetics.105.044727. Epub 2005 Sep 19.


The Q gene is largely responsible for the widespread cultivation of wheat because it confers the free-threshing character. It also pleiotropically influences many other domestication-related traits such as glume shape and tenacity, rachis fragility, spike length, plant height, and spike emergence time. We isolated the Q gene and verified its identity by analysis of knockout mutants and transformation. The Q gene has a high degree of similarity to members of the AP2 family of transcription factors. The Q allele is more abundantly transcribed than q, and the two alleles differ for a single amino acid. An isoleucine at position 329 in the Q protein leads to an abundance of homodimer formation in yeast cells, whereas a valine in the q protein appears to limit homodimer formation. Ectopic expression analysis allowed us to observe both silencing and overexpression effects of Q. Rachis fragility, glume shape, and glume tenacity mimicked the q phenotype in transgenic plants exhibiting post-transcriptional silencing of the transgene and the endogenous Q gene. Variation in spike compactness and plant height were associated with the level of transgene transcription due to the dosage effects of Q. The q allele is the more primitive, and the mutation that gave rise to Q occurred only once leading to the world's cultivated wheats.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Chromosomes, Artificial, Bacterial
  • DNA, Plant / genetics
  • Dimerization
  • Genetic Markers
  • Molecular Sequence Data
  • Phenotype
  • Phylogeny
  • Physical Chromosome Mapping
  • Plants, Genetically Modified
  • Saccharomyces cerevisiae
  • Transcription Factor AP-2 / genetics*
  • Transcription Factor AP-2 / metabolism
  • Transformation, Genetic
  • Transgenes / physiology*
  • Triticum / genetics*
  • Triticum / growth & development*
  • Two-Hybrid System Techniques


  • DNA, Plant
  • Genetic Markers
  • Transcription Factor AP-2

Associated data

  • GENBANK/AY170867
  • GENBANK/AY702955
  • GENBANK/AY702956
  • GENBANK/AY702957
  • GENBANK/AY702958
  • GENBANK/AY702959
  • GENBANK/AY702960
  • GENBANK/AY714339
  • GENBANK/AY714340
  • GENBANK/AY714341
  • GENBANK/AY714342
  • GENBANK/AY714343