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 γ-gliadin genes remain unclear.

Objectives

Dissect the effect of DNA methylation in the promoter of γ-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 TaGli-γ-2.1 on dough strength. Bisulfite analysis and 5-Aza-2′-deoxycytidine treatment were used to verify the regulation of TaGli-γ-2.1 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

TaGli-γ-2.1 was classified into a subgroup of γ-gliadin 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 TaGli-γ-2.1 expression. Treatment with 5-Aza-2′-deoxycytidine in seeds of strong gluten wheat varieties increased the expression levels of TaGli-γ-2.1. Furthermore, the accumulations of gliadin and γ-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.

中文翻译：

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TaGli-γ-2.1的启动子DNA高甲基化正向调节面包小麦的面筋强度

介绍

麦醇溶蛋白是面筋蛋白的主要成分，对最终用途小麦产品的特性和与健康相关的小麦品质具有重要作用。然而，γ-醇溶蛋白基因的功能和调控机制仍不清楚。

目标

剖析γ-麦醇溶蛋白基因启动子DNA甲基化对其表达水平和小麦面筋强度的影响。

方法

进行原核表达和还原-氧化反应以确定TaGli-γ-2.1 对面团强度的影响。亚硫酸氢盐分析和 5-Aza-2'-脱氧胞苷处理用于验证 pTaGli-γ-2.1 甲基化对TaGli-γ-2.1表达的调节。用反相高效液相色谱法测定面筋蛋白成分的含量，用面筋指数和粉质仪测定面筋强度。

结果

TaGli-γ-2.1属于γ-麦醇溶蛋白多基因家族的一个亚群，在灌浆后期优先表达。将 TaGli-γ-2.1 蛋白片段添加到强筋小麦粉中显着降低了稳定时间。pTaGli-γ-2.1 的三个 CG 基因座的高甲基化导致TaGli-γ-2.1表达降低。在强筋小麦品种种子中用5-Aza-2'-脱氧胞苷处理增加了TaGli-γ-2.1的表达水平。此外，随着面筋指数和面团稳定时间的增加，高甲基化小麦品种中麦醇溶蛋白和γ-麦醇溶蛋白的积累显着降低。

结论

pTaGli-γ-2.1 的表观遗传修饰通过调节面筋蛋白的比例影响面筋强度。pTaGli-γ-2.1的高甲基化是提高小麦品质育种中面筋强度的新型遗传资源。