A barley SS2a single base mutation at the splicing site leads to obvious changes in starch

Starch biosynthesis is a complex process that relies on the coordinated action of multiple enzymes. Resistant starch is not digested in the small intestine, thus preventing a rapid rise in the glycemic index. Starch synthase 2a (SS2a) is a key enzyme in amylopectin biosynthesis that has significant effects on starch structure and properties. In this study, we identified an ss2a null mutant (M3-1413) with a single base mutation from an ethyl methane sulfonate (EMS)-mutagenized population of barley. The mutation was located at the 3´ end of the first intron of the RNA splicing receptor (AG) site, and resulted in abnormal RNA splicing and two abnormal transcripts of ss2a, which caused the inactivation of the SS2a gene. The starch structure and properties were significantly altered in the mutant, with M3-1413 containing lower total starch and higher amylose and resistant starch levels. This study sheds light on the effect of barley ss2a null mutations on starch properties and will help to guide new applications of barley starch in the development of nutritious food products.