Promoter DNA hypermethylation of positively regulates gluten strength in bread wheat.

Introduction: Gliadins are the major components of gluten proteins with vital roles on properties of end-use wheat product and health-relate quality of wheat. However, the function and regulation mechanisms of gliadin genes remain unclear.

Objectives: Dissect the effect of DNA methylation in the promoter of -gliadin gene on its expression level and gluten strength of wheat.

Methods: The prokaryotic expression and reduction-oxidation reactions were performed to identify the effect of on dough strength. Bisulfite analysis and 5-Aza-2'-deoxycytidine treatment were used to verify the regulation of expression by pTaGli-γ-2.1 methylation. The content of gluten proteins composition was measured by RP-HPLC, and the gluten strength was measured by Gluten Index and Farinograph.

Results: was classified into a subgroup of multigene family and was preferentially expressed in the later period of grain filling. Addition of TaGli-γ-2.1 protein fragment into strong gluten wheat flour significantly decreased the stability time. Hypermethylation of three CG loci of pTaGli-γ-2.1 conferred to lower expression. Treatment with 5-Aza-2'-deoxycytidine in seeds of strong gluten wheat varieties increased the expression levels of . Furthermore, the accumulations of gliadin and -gliadin were significantly decreased in hypermethylated wheat varieties, corresponding with the increasing of gluten index and dough stability time.

Conclusion: Epigenetic modification of pTaGli-γ-2.1 affected gluten strength by modulating the proportion of gluten proteins. Hypermethylation of pTaGli-γ-2.1 is a novel genetic resource for enhancing gluten strength in wheat quality breeding.