Abstract
Seed storage proteins in wheat endosperm, particularly high-molecular-weight glutenin subunits (HMW-GS), are primary determinants of dough properties, and affect both end-use quality and grain utilization of wheat (Triticum aestivum L). In order to investigate the interactive effects between the transgenically overexpressed 1Ax1 subunit with different HMW-GS on dough quality traits, we developed a set of 8 introgression lines (ILs) overexpressing the transgenic HMW-glutenin subunit 1Ax1 by introgression of this transgene from transgenic line B102-1-2/1 into an elite Chinese wheat variety Chuanmai107 (C107), using conventional crossing and backcrossing breeding technique. The donor C107 strain lacks 1Ax1 but contains the HMW-GS pairs 1Dx2+1Dy12 and 1Bx7+1By9. The resultant ILs showed robust and stable expression of 1Ax1 even after five generations of self-pollination, and crossing/backcrossing three times. In addition, overexpression of 1Ax1 was compensated by the endogenous gluten proteins. All ILs exhibited superior agronomic performance when compared to the transgenic parent line, B102-1-2/1. Mixograph results demonstrated that overexpressed 1Ax1 significantly improved dough strength, resistance to extension and over-mixing tolerance, in the targeted wheat cultivar C107. Further, comparisons among the ILs showed the interactive effects of endogenous subunits on dough properties when 1Ax1 was overexpressed: subunit pair 17+18 contributed to increased over-mixing tolerance of the dough; expression of the Glu-D1 allele maintained an appropriate balance between x-type and y-type subunits and thereby improved dough quality. It is consistent with ILs C4 (HMW-GS are 1, 17+18, 2+12) had the highest gluten index and Zeleny sedimentation value. This study demonstrates that wheat quality could be improved by using transgenic wheat overexpressing HMW-GS and the feasibility of using such transgenic lines in wheat quality breeding programs.
Highlights
Wheat is one of the most important international crops known for its adaptability to various climatic conditions
Eight introgression lines (C1a, C1b, C2a, C2b, C3a, C3b, C4a and C4b) overexpressing the 1Ax1 transgene along with a 1Ax1-negative control C0 and parental lines were subjected to further analyses as described below
Total protein contents in the grains ranged from 14.9% (12.3%) to 17.0% (14.6%) for the recurrent parent cultivar C107 and line C4a introgressed with the 1Ax1 transgene (Table 1)
Summary
Wheat is one of the most important international crops known for its adaptability to various climatic conditions. Wheat grain is widely used in several flour-based foods primarily due to its unique end-use properties conferred by gluten proteins [1]. Among these proteins, glutenins and gliadins, compose the majority of seed storage proteins and primarily determine the viscoelastic properties of wheat dough. HMW-GS are major determinants of dough mixing properties and largely determine the end-use quality of wheat [2,3]. Allelic variations in the HMW-GS composition lead to variations in the structures of glutenin polymers, and affect the rheological properties of dough and wheat end-use quality [5,6]. Previous studies have correlated stronger dough and better bread-making quality to the HMW-GS subunit 1Ax1 and subunits pair 1Dx5+1Dy10 [2,7,8]
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