Molecular characterization of the major wheat domestication gene Q.
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.
Simons
Kristin J
KJ
Department of Plant Sciences, North Dakota State University, Fargo, North Dakota 58105, USA.
Fellers
John P
JP
Trick
Harold N
HN
Zhang
Zengcui
Z
Tai
Yin-Shan
YS
Gill
Bikram S
BS
Faris
Justin D
JD
D022202:Chromosomes, Artificial, Bacterial; D018744:DNA, Plant / Q000235:genetics; D019281:Dimerization; D005819:Genetic Markers; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D020161:Physical Chromosome Mapping; D030821:Plants, Genetically Modified; D012441:Saccharomyces cerevisiae; D050656:Transcription Factor AP-2 / Q000235:genetics* / Q000378:metabolism; D014170:Transformation, Genetic; D019076:Transgenes / Q000502:physiology*; D014908:Triticum / Q000235:genetics* / Q000254:growth & development*; D020798:Two-Hybrid System Techniques
D018744:DNA, Plant; D005819:Genetic Markers; D050656:Transcription Factor AP-2