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High molecular weight glutenin subunits (HMW-GS), major components of seed storage proteins in wheat, have large effects on processing quality. GLU-1 genes encode HMW-GS and their expression is mainly controlled at the transcriptional level by interactions between cis-regulatory elements and transcription factors. We previously identified an Aux/IAA transcription factor TaIAA10-6D that bound to a conserved cis-regulatory module CCRM1-1, the most essential conserved cis-regulatory module in GLU-1. Here, we confirmed the binding of TaIAA10-6D to CCRM1-1 using yeast one hybrid and dual-luciferase reporter assays. The enhanced expression of TaIAA10-6D suppressed glutenin accumulation and increased gliadin content. Dynamic transcriptome analyses revealed that TaIAA10-6D overexpression down-regulated glutenin and gliadin genes during an early stage of grain filling, but up-regulated gliadin genes during a late stage probably by endoplasmic reticulum stress, accounting for its effect on the trade-off between glutenin and gliadin. Rheological property and processing quality assays showed that TaIAA10-6D overproduction reduced stabilization time and bread quality, but enhanced cookie quality. Overexpression of TaIAA10-6D also reduced plant height, leaf size, kernel number and grain yield. We identified two major haplotypes of TaIAA10-6D, Hap I and Hap II, and developed a breeding-friendly diagnostic marker. Hap I conferred higher expression of TaIAA10-6D and concomitantly reduced plant height and kernel number, but had little effect on grain yield, contributing to lodging resistance without yield penalty. Hap I was subjected to positive selection in breeding. The findings provide a useful gene for wheat improvement and broaden insights into the regulatory machinery underpinning auxin-mediated quality formation, plant morphogenesis and yield gain.

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National Natural Science Foundation of China China Postdoctoral Science Foundation Chinese Academy of Agricultural Sciences (CAAS)