Abstract
SummaryArabinoxylan (AX) is the dominant component within wheat (Triticum aestivum L.) endosperm cell walls, accounting for 70% of the polysaccharide. The viscosity of aqueous extracts from wheat grain is a key trait influencing the processing for various end uses, and this is largely determined by the properties of endosperm AX. We have previously shown dramatic effects on endosperm AX in transgenic wheat by down‐regulating either TaGT43_2 or TaGT47_2 genes (orthologues to IRX9 and IRX10 in Arabidopsis, respectively) implicated in AX chain extension and the TaXAT1 gene responsible for monosubstitution by 3‐linked arabinose. Here, we use these transgenic lines to investigate the relationship between amounts of AX in soluble and insoluble fractions, the chain‐length distribution of these measured by intrinsic viscosity and the overall effect on extract viscosity. In transgenic lines expressing either the TaGT43_2 or TaGT47_2 RNAi transgenes, the intrinsic viscosities of water‐extractable (WE‐AX) and of a water‐insoluble alkaline‐extracted fraction (AE‐AX) were decreased by between 10% and 50% compared to control lines. In TaXAT1 RNAi lines, there was a 15% decrease in intrinsic viscosity of WE‐AX but no consistent effect on that of AE‐AX. All transgenic lines showed decreases in extract viscosity with larger effects in TaGT43_2 and TaGT47_2 RNAi lines (by up to sixfold) than in TaXAT1 RNAi lines (by twofold). These effects were explained by the decreases in amount and chain length of WE‐AX, with decreases in amount having the greater influence. Extract viscosity from wheat grain can therefore be greatly decreased by suppression of single gene targets.
Highlights
The cells of the wheat starchy endosperm have primary cell walls which are laid down as the cells expand rapidly to accommodate the deposition of starch and storage proteins
We selected three independent lines, each carrying RNAi constructs driven by the HMW1Dx5 endosperm-specific promoter, targeting three AX biosynthetic genes in hexaploid wheat: TaGT43_2 and TaGT47_2 as described in Lovegrove et al (2013) and TaXAT1 as described in Anders et al (2012)
We have previously described the profound effects on AX of suppression of TaGT43_2, TaGT47_2 and TaXAT1 genes by RNAi in wheat endosperm (Anders et al, 2012; Lovegrove et al, 2013)
Summary
The cells of the wheat starchy endosperm have primary cell walls which are laid down as the cells expand rapidly to accommodate the deposition of starch and storage proteins. The polysaccharide composition of these walls is unusual, having a low cellulose component (3%), 7% glucomannan, 20% b-(1,3;1,4) glucan and 70% arabinoxylan (AX) (Mares and Stone, 1973). Compared to the AX or glucuronoarabinoxylan (GAX) in the cell walls of other tissues of grasses, the endosperm AX has a relatively simple structure, with low amounts of FA, lacking glucuronyl substitution and is nonacetylated at maturity. The simple AX structure and low cellulose content of wheat starchy endosperm cell walls may allow them to be readily digested during germination, facilitating access to the reserves (Burton and Fincher, 2014)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
