Analysis of Beta-D-glucan Biosynthetic Genes in Oat Reveals Glucan Synthesis regulation by Light.

BACKGROUND AND AIMS Oat (Avena sativa L.) has human health benefits when consumed as a whole grain food, attributed to the high content of (1,3;1,4)-β-D-glucan (mixed-linkage glucan [MLG]), but little is known about the synthase genes and synthesis mechanism of these polysaccharides in this species. METHODS Concentration of oat MLG under different light intensities was measured by a standard enzymatic approach and further verified by immunoelectron microscopy. The effect of light intensity on MLG synthase genes was examined by RT-qPCR and Western blot analyses. The pattern of expression directed by the promoter of the oat MLG synthase gene was also investigated by histochemical GUS analysis. KEY RESULTS The oat orthologs of genes implicated in the synthesis of MLG in other cereals, including cellulose synthase-like (Csl) F, H, and J gene families were defined. Transcript profiling of these genes across oat tissues indicated that AsCslF6 transcripts dominated. Under high light intensities, the expression of AsCslF6, a major isoform of the MLG synthase genes, increased to more than 30% of the dark growth control. The amount of MLG in oat rose from 0.07% to 1.06% with the light intensity increased. Histochemical tests showed that the AsCslF6 gene promoter preferentially directs GUS expression under high light intensity conditions. CONCLUSIONS Oat MLG synthesis is regulated by light. High light intensity up-regulates the expression of the MLG synthase AsCslF6 gene, leading to an increase in the amount of MLG in the oat leaves.