Manipulation of StPTST1 Affects Starch Content and Physicochemical Properties of Potato (Solanum tuberosum L.).

Foods rich in amylose and resistant starch (RS) hold great potential for improving human health. Granule-bound starch synthase (GBSS) is a key enzyme for amylose biosynthesis and its interaction partner, PROTEIN TARGETING TO STARCH1 (PTST1), has been characterized. In this study, we generated overexpression and knockout transgenic plants of StPTST1 to investigate its effect on starch content and physicochemical properties. Aligning with the presence of carbohydrate-binding module in the protein, StPTST1 possesses starch-binding capacity. stptst1 knockout mutants showed a reduction in both total starch and amylose contents in tubers. Analysis of the pasting properties showed that peak viscosity (PV), trough viscosity (TV), breakdown viscosity (BV), final viscosity (FV), and setback viscosity (SV) were all increased in the mutants compared to that in the WT plants. Overexpression of StPTST1 led to an increase in the contents of amylose, RS, and total starch. Moreover, the proportion of short chains (0 < DP < 32) in amylopectin of StPTST1-overexpressing plants was reduced. These data demonstrated that both stptst1 mutants and StPTST1-overexpressing plants were altered in starch content and physicochemical properties. Elucidating the function of StPTST1 deepens our understanding of starch biosynthesis in potato and highlights its potential for enhancing potato nutritional quality.