Thomas Burr Osborne Medal Award
G. B. FINCHER (1)
(1) University of Adelaide, Glen Osmond, Australia
2013 AACCI Annual Meeting
http://dx.doi.org/10.1094/CPLEX-2013-1226-21W
Cell walls are relatively minor constituents of most cereal grains, but they exert a disproportionately large influence on grain processing, food quality and human health. Wall polysaccharides are components of dietary fibre, which reduces the risk of contracting serious diseases, including type II diabetes, colorectal cancer and cardiovascular disease. In cereals, arabinoxylans appear to be the core wall polysaccharides of the starchy endosperm and aleurone, while (1,3;1,4)-beta-glucans are abundant in walls of some, but not all cereal endosperm. Following chemical and structural analyses of these polysaccharides, attention turned to the enzymes involved in their biosynthesis, re-modelling and degradation. Hydrolytic enzymes were purified and characterized, and crystal structures enabled the detailed mechanisms of action of the hydrolases to be defined. With the advent of molecular biology, genes encoding the enzymes were cloned and expression patterns of individual genes were monitored in a range of tissues. In the case of the wall polysaccharide synthases, progress was considerably slower. The enzymes are membrane-bound and not amenable to purification or to in vitro assays. Without amino acid sequence information, it proved difficult to identify the genes that encode these enzymes. However, emerging methods of functional genomics, linked with molecular genetics and molecular breeding, together provided breakthroughs that led to the identification and characterization of genes encoding wall polysaccharide synthases, including (1,3;1,4)-beta-glucan synthases. Functional genomics culminated in late 2012 with the publication of scaffold genome sequences for wheat and barley. Genome sequencing technologies are continuing to expand our understanding of cereal chemistry and will undoubtedly prove invaluable in cereal grain utilization and processing in the future.
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