Expression of Puroindoline a in Durum Wheat Affects Milling and Pasting Properties.

Qiong Wang,Xiaoyan Li,Guangxiao Yang,Yin Li,Pandi Wang,Guangyuan He,Fusheng Sun

doi:10.3389/fpls.2019.00482

Abstract

Durum wheat has limited culinary utilizations partly due to its extremely hard kernel texture. Previously, we developed transgenic durum wheat lines with expression of the wildtype Puroindoline a (Pina) and characterized PINA’s effects on kernel hardness, total flour yield and dough mixing properties in durum wheat. The medium-hard kernel texture is potentially useful for exploring culinary applications of durum wheat. In the present study, we examined the milling parameters and flour attributes of the transgenic lines, including particle size distribution, damaged starch and water binding capacity. PINA expression results in increased break and reduction flour yield but decreased shorts. PINA expression also leads to finer flour particles and decreased starch damage. Interestingly, PINA transgenic lines showed increased peak viscosity and breakdown viscosity but leave other flour pasting parameters generally unaltered. PINA transgenic lines were associated with increased small monomeric proteins, appearing to affect gluten aggregation. Our data together with several previous results highlight distinct effects of PINs on pasting properties depending on species and variety. The medium-hard kernel texture together with improved pasting parameters may be valuable for producing a broader range of end-products from durum wheat.

Highlights

Of the global wheat production, ∼93% are contributed by allohexaploidy common wheat (Triticum aestivum L.; 2n = 42, AABBDD) and ∼7% by allotetraploidy durum wheat (Triticum turgidum ssp durum; 2n = 28, AABB; North Dakota Wheat Commission, 2015)
PINA overexpression in the transgenic lines was confirmed when compared with the endogenous PINA in Chinese Spring (CS) detected by western blotting (Supplementary Figure S1)
Besides the medium-hard kernel texture and increased flour yield resulted from PINA overexpression that is confirmed here, detailed investigations on flour and milling attributes show that PINA overexpression increases flour yield, lower starch damage and, affects flour particle size and water absorption in durum wheat

Summary

Introduction

The limited production and use of durum wheat are likely related to two reasons: (i) durum wheat’s extremely-hard kernels require specialized milling equipments; (ii) the milling product, semolina, has large particle size and high level of damaged starch, limited the culinary applications (Boehm et al, 2017a,b). The extremely-hard kernel texture of durum wheat (hardness index, HI > 80) is due to lack of the D genome and the hardness (Ha) locus, which is located at the distal end of chromosome 5DS and harbors two causal genes for kernel hardness, Puroindoline a and b (Pina and Pinb; Morris, 2002; Bhave and Morris, 2008a,b). Expression of wildtype Pina and Pinb in common wheat gives a soft kernel phenotype (HI < 40), while specific Pina and/or Pinb alleles of deletions or mutations result in hard kernel (Giroux and Morris, 1997, 1998; Beecher et al, 2002). Transgenic studies well proved that addition of PINA in the absence of starch-bound PINB, or addition of PINB in the absence of starch-bound PINA, leads to intermediate kernel hardness, demonstrating that the starch-bound PINA and PINB (friabilin) rather than total PINs’ content is the factor controlling kernel hardness (Hogg et al, 2004, 2005; Martin et al, 2006, 2007; Swan et al, 2006; Wanjugi et al, 2007)

Methods

Results

Conclusion