Foods with high amylose and resistant starch (RS) contents have great potential to enhance human health. In this study, cassava soluble starch synthase MeSSIII-1 gene mutants were generated using CRISPR/Cas9 system. The results showed that the storage roots of messiii-1 mutants had higher contents of amylose, RS, and total starch than those in CK. The rates of small and large-sized starch granules were increased. Additionally, amylopectin starch in messiii-1 mutants had a higher proportion of medium- and long- chains, and a lower proportion of short-chains than those in CK. The onset, peak, and conclusion temperatures of starch gelatinization in messiii-1 mutants were significantly lower than those in CK, and the peak viscosity, trough viscosity and final viscosity all increased. MeSSIII-1 mutation could increase the contents of sucrose, glucose, and fructose in cassava storage roots. We hypothesize that these soluble sugars serve a dual role: they provide the necessary carbon source for starch synthesis and act as sugar signals to trigger the transcriptional reprogramming of genes involved in starch biosynthesis. This process results in a collective enhancement of amylose, RS, and total starch contents, accompanied by changes in starch granule morphology, fine structure, and physicochemical properties.
Keywords: CRISPR/Cas9; Cassava; MeSSIII-1; RS; Starch properties.
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