Loss of TaIRX9b gene function in wheat decreases chain length and amount of arabinoxylan in grain but increases cross-linking

A - Papers appearing in refereed journals

Pellny, T. K., Wood, A., Freeman, J., Halsey, K., Plummer, A., Kosik, O., Shewry, P. R., Lovegrove, A., Phillips, A. L. and Mitchell, R. A. C. 2020. Loss of TaIRX9b gene function in wheat decreases chain length and amount of arabinoxylan in grain but increases cross-linking. Plant Biotechnology Journal. pp. 1-12. https://doi.org/10.1111/pbi.13393

AuthorsPellny, T. K., Wood, A., Freeman, J., Halsey, K., Plummer, A., Kosik, O., Shewry, P. R., Lovegrove, A., Phillips, A. L. and Mitchell, R. A. C.
Abstract

Wheat contains abundant xylan in cell walls of all tissues, but in endosperm there is an unusual form of xylan substituted only by arabinose (arabinoxylan; AX) that has long chains and low levels of feruloylation, a fraction of which is extractable in water (WE-AX). WE-AX acts as soluble dietary fibre but also gives rise to viscous extracts from grain, a detrimental trait for some non-food uses of wheat. Here we show that a glycosyl transferase family 43 wheat gene abundantly expressed in endosperm complements the Arabidopsis irx9 mutant and so name the three homoeologous genes TaIRX9b. We generated wheat lines with a constitutive knock-out of TaIRX9b by stacking loss-of-function alleles for these homeologues from a mutagenized hexaploid wheat population resulting in decreases in grain extract viscosity of 50-80%. The amount and chain length of WE-AX molecules from grain of these triple stack lines was decreased accounting for the changes in extract viscosity. Imaging of immature wheat grain sections of triple stacks showed abolition of immunolabelling in endosperm with LM11 antibody that recognises epitopes in AX, but also showed apparently normal cell size and shape in all cell types, including endosperm. We identified differentially expressed genes from endosperm of triple stacks suggesting that compensatory changes occur to maintain this endosperm cell wall integrity. Consistent with this, we observed increased ferulate dimerisation and increased cross-linking of WE-AX molecules in triple stacks. These novel wheat lines lacking functional TaIRX9b therefore provide insight into control of wheat endosperm cell walls.

KeywordsWheat grain viscosity; IRX9; Xylan; Ferulic acid; Cell wall integrity
Year of Publication2020
JournalPlant Biotechnology Journal
Journal citationpp. 1-12
Digital Object Identifier (DOI)https://doi.org/10.1111/pbi.13393
Open accessPublished as bronze (free) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeLow viscosity wheat for improved properties for fermentation and animal feed
Xylan arabinosyl transferases: identification and characterisation of their role in determining properties of grass cell walls
15AGRITECHCAT4: Novel low viscosity wheats for distilling
DFW - Designing Future Wheat - Work package 2 (WP2) - Added value and resilience
Publisher's version
Supplemental file
Output statusPublished
Publication dates
Online22 May 2020
Publication process dates
Accepted19 Apr 2020
PublisherWiley
ISSN1467-7644

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