Dietary Fibre: Wheat Genes for Enhanced Human Health

Abstract

Dietary fibre (DF) has been shown to be a vital component of diet for human health, decreasing the risk of cardiovascular disease, type II diabetes and possibly bowel cancer. DF in wheat flour is derived from the cell walls of the starchy endosperm, which is principally composed (~70 %) of the polysaccharide arabinoxylan (AX). Diversity screens of elite wheat germplasm have established that variation in total and water-extractable AX within flour exists and has high heritability. Identification of genes which determine AX content will assist in introduction of high DF alleles into appropriate backgrounds. We identified candidate genes for the synthesis and feruloylation of AX from bioinformatics approaches. Using RNAi suppression of genes in wheat endosperm, we have shown that a glycosyl transferase (GT) family 61 gene is responsible for nearly all mono-substitution of xylose by arabinose on AX, and that genes in GT43 and GT47 families are responsible for the synthesis of the xylan backbone in AX. Using mapping populations derived from crosses of high AX x normal AX varieties, we are also seeking to identify QTLs for high AX. This combination of forward and reverse genetics will accelerate the introduction of the high fibre alleles into modern commercial wheat varieties.