Altered starch composition and improved bread quality in novel wheat mutant reveal key transcriptional regulators

Wheat starch composition and content significantly influence the processing and end-use quality of flour. In this study, we characterized a novel wheat mutant (M393) generated via γ-ray mutagenesis, which exhibited altered starch content and superior bread-making performance compared to the wild type (WT). Comprehensive comparison analysis shows that the mutant M393 has longer dough stability time, higher tensile strength and better ductility than the wild type, and the volume of bread is larger, the texture of bread is finer, and the taste of bread is better. Microscopic observations, together with laser diffraction particle size analysis, revealed smaller starch granules and an increased proportion of B-type granules in M393.The total starch and amylose content of the mutant M393 were significantly decreased, while the amylopectin content was increased. Transcriptomic analyses revealed downregulated expression of the GBSS gene, which is responsible for amylose synthesis, while genes related to amylopectin synthesis (SBE, SS, and DBE) were upregulated, corresponding to the shifts in starch composition. In addition, a co-expression network of transcription factors and starch synthesis genes was constructed, and new transcription factors such as MYB89, SBP91, bHLH131, HD-ZIP67, and HD-ZIP66 were identified as putative regulators that may be involved in the expression of starch genes. The results of this study provide new insights into the transcriptional regulation of starch biosynthesis and provide a valuable theoretical basis for breeding wheat varieties with better processing quality.