New alleles of the wheat domestication gene Q reveal multiple roles in growth and reproductive development [RESEARCH REPORT]

Julian R. Greenwood, E. Jean Finnegan, Nobuyoshi Watanabe, Ben Trevaskis, and Steve M. Swain

The advantages of free threshing in wheat led to the selection of the domesticated Q allele which is now present in almost all modern wheat varieties. Q and the pre-domestication allele, q, encode an AP2 transcription factor with the domesticated allele conferring a free threshing character and a subcompact (i.e. partially compact) inflorescence (spike). We demonstrate that mutations in the miR172-binding site of the Q gene are sufficient to increase transcript levels via a reduction in miRNA dependent degradation, consistent with the conclusion that a SNP in the miRNA-binding site of Q relative to q was essential in defining the modern Q allele. We also describe novel gain- and loss-of-function alleles of Q and use these to define new roles for this gene in spike development. Q is required for the suppression of 'sham ramification' and increased Q expression can lead to the formation of ectopic florets and spikelets (specialized inflorescence branches that bear florets and grains) resulting in a deviation from the canonical spike and spikelet structures of domesticated wheat.

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