The Plant journal : for cell and molecular biology | 2021
TaNAC100 acts as an integrator of seed protein and starch synthesis conferring pleiotropic effects on agronomic traits in wheat.
Abstract
High-molecular-weight glutenin subunits (HMW-GS) are major components of seed storage proteins (SSPs) and largely determine the processing properties of wheat flour. HMW-GS are encoded by the GLU-1 loci and regulated at the transcriptional level by interaction between cis-elements and transcription factors (TFs). We recently validated the function of conserved cis-regulatory modules (CCRMs) in GLU-1 promoters, but their interacting TFs remained uncharacterized. Here we identified a CCRM-binding NAC protein, TaNAC100, through yeast one hybrid (Y1H) library screening. Transactivation assays demonstrated that TaNAC100 could bind to the GLU-1 promoters and repress their transcription activity in tobacco. Overexpression of TaNAC100 in wheat significantly reduced the contents of HMW-GS and other SSPs as well as total seed proteins. This was confirmed by transcriptome analyses. Conversely, enhanced expression of TaNAC100 increased seed starch contents and expression of key starch synthesis-related genes, such as TaGBSS1 and TaSUS2. Y1H assays also indicated TaNAC100 binding with the promoters of TaGBSS1 and TaSUS2. These results suggest that TaNAC100 functions as a hub controlling seed protein and starch synthesis. Phenotypic analyses showed that TaNAC100 overexpression repressed plant height, increased heading date, and promoted seed size and thousand kernel weight. We also investigated sequence variations in a panel of cultivars population, but didn t identify significant association of TaNCA100 haplotypes with agronomic traits. The findings not only uncover a useful gene for wheat breeding but also provide an entry point to reveal the mechanism underlying metabolic balance of seed storage products.