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Barley grain composition and metabolism over development and germination.
A. BLENNOW (1). (1) Univ of Copenhagen, Frederiksberg C, Denmark

Starch is a multipurpose polysaccharide with tremendous importance within food, feed and fuel and is now increasingly developed for advanced renewable materials applications. Direct starch bioengineering of cereals is emerging following progress in our understanding of starch biosynthesis, and genes involved in this process permitting genetic modification of crops in a rational manner to produce novel designer starches with new and improved functionality. We used barley as a model and targeted two important starch features, the phosphate content which has potential industrial applications and amylose content having valuable food, feed and biomaterial applications. To this end, we overexpressed the potato starch phosphorylation enzyme, Glucan Water Dikinase (GWD) and suppressed the 3 existing isoforms of starch branching enzyme (SBE) by RNAi technology, in barley.  We reached a 10-fold increase in starch-phosphate content and ~99% amylose content, respectively, in in our transgenic barley lines. For the ~99% amylose line, amylose-only, AO) <i>in vitro</i> enzymatic starch hydrolysis showed 2.2-fold higher resistant starch than the control starch. Our approach can be extended to other cereal systems and we thoroughly tested possible side effects using microscopy, chemical compositional analysis and GC-MS metabolite profiling approach to verify GM “substantial equivalence” criteria for the new lines. Typically, the AO line showed reduced yield and starch content and higher and altered sugar composition.

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