Genome-Informed Genetic Engineering and Gene Editing in Sorghum

Sorghum is a major staple cereal with over 500 million people worldwide dependent on it every day in sub-Saharan Africa and India. In the western world, sorghum is predominantly utilized as animal feed and bio-industrial end uses. We have used genetic engineering and genomics approaches in parallel to improve the key quality parameters of sorghum: starch, protein and sugars. Association studies have identified a number of genes that have significant implications for human food uses, in particular the GBSS (waxy) and pullulanase debranching enzymes, which confer enhanced digestibility in monogastric animals. Pullullanase allelic variants encoding two amino acid substitutions have higher enzyme activity which significantly alters starch branching patterns and molecule size in both amylose and amylopectin. We have also expressed some of the key genes ectopically using transgenic approaches. In addition we have manipulated the kafirin seed storage proteins and the protein:starch matrix. This has led to altered grain size, digestibility and end-use processing qualities. There are also implications for the growth of plant biomass which will be discussed.