Overriding the co‐limiting import of carbon and energy into tuber amyloplasts increases the starch content and yield of transgenic potato plants

Abstract

Summary: Transgenic potato (Solanum tuberosum) plants simultaneously over‐expressing a pea (Pisum sativum) glucose‐6‐phosphate/phosphate translocator (GPT) and anArabidopsis thalianaadenylate translocator (NTT1) in tubers were generated. Double transformants exhibited an enhanced tuber yield of up to 19%, concomitant with an additional increased starch content of up to 28%, compared with control plants. The total starch content produced in tubers per plant was calculated to be increased by up to 44% in double transformants relative to the wild‐type. Single over‐expression of either gene had no effect on tuber starch content or tuber yield, suggesting that starch formation within amyloplasts is co‐limited by the import of energy and the supply of carbon skeletons. As total adenosine diphosphate‐glucose pyrophosphorylase and starch synthase activities remained unchanged in double transformants relative to the wild‐type, they cannot account for the increased starch content found in tubers of double transformants. Rather, an optimized supply of amyloplasts with adenosine triphosphate and glucose‐6‐phosphate seems to favour increased starch synthesis, resulting in plants with increased starch content and yield of tubers.