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Understanding roles of starch synthases in the determination of starch structure and function in barley. Z. LI (1), A. Regina (1), M. K. Morell (2), S. A. Jobling (3). (1) CSIRO Plant Industry, Canberra, ACT, AB, Australia; (2) International Rice Research Institute, Manila, AB, Philippines; (3) CSIRO Plant Indstry, Canberra, ACT, AB, Australia Our group is studying the relationship between starch structure and nutritional properties of cereal starches. The endosperm of barley grain typically contains ~50-60% starch composed of ~25% amylose and ~75% amylopectin. Starch synthases are one of four classes of enzymes involving in cereal starch biosynthesis. Starch synthases transfer glucose from ADP-glucose to the non-reducing end of pre-existing a-(1-4)-linked glucosyl chains of starch. Four of five classes of starch synthases play roles in the synthesis of amylopectin. Each class of starch synthases catalyse the synthesis of different lengths of glucosyl chains of starch. Loss of function mutations of starch synthase genes provides a powerful approach to study the roles of starch synthases in the determination of starch structure and function in barley. Some of these changes in starch also make the modified starch less digestible by increasing the level of resistant starch content of barley grains. The roles of these starch synthases in the determination of starch structure, function and starch content will be discussed.    View Presentation