The Qc5 Allele Increases Wheat Bread-Making Quality by Regulating SPA and SPR

Abstract

Common wheat (Triticum aestivumL.) is an important food crop with a unique processing quality. TheQgene positively regulates the processing quality of wheat, but the underlying mechanism remains unclear. Here, a newQallele (Q^c5) responsible for compact spikes and good bread performance was identified. Compared with theQallele widely distributed in modern common wheat cultivars,Q^c5had a missense mutation outside the miRNA172-binding site. This missense mutation led to a more compact messenger RNA (mRNA) secondary structure around the miRNA172-binding region, resulting in increasedQ^c5expression during the spike development stage and a consequent increase in spike density. Furthermore, this missense mutation weakened the physical interaction between Q^c5and storage protein activator (SPA) in seeds and suppressed the expression ofstorage protein repressor(SPR). These changes increased the grain protein content and improved the bread-making quality of wheat. In conclusion, a missense mutation increasesQexpression because of the resulting highly folded mRNA secondary structure around the miRNA172-binding site. Furthermore, this mutation improves the bread-making quality of wheat by repressing the expression ofSPRand influencing the physical interaction between Q and SPA. These findings provide new insights into the miRNA172-directed regulation of gene expression, with implications for wheat breeding.

Keywords:breeding;seed storage proteins;mRNA secondary structure;microRNA;processing quality