Targeting granule initiation and amyloplast structure to create giant starch granules in wheat

Starch granule size influences the functional, digestive, and processing qualities of starch, but its genetic control is poorly understood. Here, we demonstrate that both space and substrate constraints limit starch granule size in wheat and provide an approach to achieve substantial increases in granule size. Wheat starch contains large A-type and small B-type granules. To increase A-type granule size, we mutated the plastid division component PARALOG OF ARC 6 (PARC6), which increases amyloplast size and the space available for granule growth, and B-GRANULE CONTENT 1 (BGC1), which reduces granule initiations and competition between growing granules. The parc6 bgc1 double mutant produced giant granules that were more than double the size of typical A-type granules. We demonstrate that the size increase affects functional properties, including viscosity and pasting temperature. Overall, by targeting both constraints, we created a giant cereal starch that has not been observed in nature, with altered physicochemical properties that can be used in food and industrial applications.