Effect of different Wx protein combinations on wheat starch biosynthesis in developing endosperm.

【Objective】 This study was to elucidate the difference in starch physiochemical properties among wheat cultivars differing in Wx protein combinations through the comparison of starch accumulation and activities of starch biosynthetic enzymes.【Method】 The accumulation of amylose and amylopectin in developing endosperm from 14 wheat cultivars with six types of Wx protein combinations were investigated,together with activities of four key enzymes involved in starch biosynthesis such as ADP-glucose pyrophosphorylase(AGPase),soluble starch synthase(SSS),granule bound starch synthase(GBSS),and starch branching enzyme(SBE).【Result】 The number and type of Wx protein had a significant influence on activities of starch biosynthetic enzymes and the accumulation of amylose and amylopectin in developing endosperm.The activities of starch biosynthetic enzymes increased with the number of Wx protein,especially for GBSS,together with the amylose content in grain.The Wx-B1 protein deficiency induced the lowest GBSS activity and amylose content in grain,then was the Wx-D1 protein,and the effect of Wx-A1 protein deficiency was the least.The activities of four starch biosynthetic enzymes correlated to each other significantly,and also correlated to the number of Wx protein,amylose and amylopectin content in grain,which suggested the biosynthesis of amylose and amylopectin in developing endosperm were interacted and synchronous.【Conclusion】 The Wx allele is one of the most determinant factors for amylose content for it can control the activity of GBSS through the number and type of Wx protein and affect other starch biosynthetic enzymes indirectly,then the synthesis of amylose and amylopectin,which result in different starch physiochemical properties and noodle quality finally.