Altered plastidic ATP/ADP-transporter activity influences potato (Solanum tuberosum L.) tuber morphology, yield and composition of tuber starch

The metabolic function of the plastidic ATP/ADP transporter (AATP) in heter otrophic plastids was examined in transgenic potato plants that exhibited i ncreased or decreased amounts of the protein. Altered mRNA levels correlate d with activities of the plastidic ATP/ADP transporter. Potato tubers with decreased plastidic ATP/ADP transporter activities exhibited reduced starch contents whereas sense lines accumulated increased amounts of tuber starch . Starch from wild-type tubers had an amylose content of 18.8%, starch from antisense plants contained 11.5-18.0% amylose, whereas starch from sense p lants had levels of 22.7-27.0%. The differences in physiological parameters were accompanied with altered tuber morphology. These changes are discusse d with respect to the stromal ATP supply during starch biosynthesis.