Homeoallelic Variation in Oat Hemicellulose Biosynthesis Genes

In seeds of oat (Avena spp., x = 7), (1,3;1,4) β-D-glucans constitute a fundamental component of the endosperm and are a primary determinant of soluble fiber content. Precursors for β-glucan biosynthesis are derived from primary starch and cellulose metabolism. ADP-glucose pyrophosphorylase (AGPase), encoded by the AGP gene, is responsible for the first committed step in ADP-glucose biosynthesis. UDP-glucose pyrophosphorylase (UGPase), encoded by the UGP gene, catalyzes the reversible conversion of glucose-1-phosphate to UDP-glucose. Products of the cellulose synthase A6 gene (CESA6) are implicated in cellulose deposition in the secondary cell wall during seed endosperm development. Here, we present the sequences of the A, C, and D genome alleles of AGP, UGP, and the CESA6 genes in six cultivars of A. sativa, as well as their orthologs in A. wiestii (AA), A. ventricosa (CC), and A. canariensis (putative DD). We further present data on alternative splice sites and differential expression of homeoalleles and discuss the implications of our data for characterizing polysaccharide biosynthesis and deposition in the oat grain, molecular breeding approaches, and understanding the nature of epistatic homeoallelic interactions in complex polyploids.