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microRNA172 plays a crucial role in wheat spike morphogenesis and grain threshability
- Debernardi, Juan Manuel, Lin, Huiqiong, Faris, Justin D., Dubcovsky, Jorge, Chuck, George
- Development 2017 v.144 pp. 1966-1975
- Triticum aestivum, alleles, binding sites, domestication, florets, gene overexpression, microRNA, morphogenesis, mutants, single nucleotide polymorphism, transcription (genetics), transcription factors, wheat, wild relatives
- Wheat domestication from wild species involved mutations in the Q gene. The q allele (wild wheats) is associated with elongated spikes and hulled grains, whereas the mutant Q allele (domesticated wheats) confers subcompact spikes and free-threshing grains. Previous studies showed that Q encodes an AP2-like transcription factor, but the causal polymorphism of the domestication traits remained unclear. Here, we show that the interaction between microRNA172 (miR172) and the Q allele is reduced by a single nucleotide polymorphism in the miRNA binding site. Inhibition of miR172 activity by a miRNA target mimic resulted in compact spikes and transition from glumes to florets in apical spikelets. By contrast, overexpression of miR172 was sufficient to induce elongated spikes and non-free-threshing grains, similar to those observed in three Q loss-of-function mutations. These lines showed transitions from florets to glumes in the basal spikelets. These localized homeotic changes were associated with opposing miR172/Q gradients along the spike. We propose that the selection of a nucleotide change at the miR172 binding site of Q contributed to subcompact spikes and free-threshing grains during wheat domestication.