cqvip:A plastidic adenosine triphosphate(ATP)/adenosine diphosphate(ADP) transporter(AATP) is responsible for importing ATP from the cytosol into plastids. In dicotyledonous plants, increasing ATP supply is a potential way to facilitate anabolic synthesis in heterotrophic plastids. In this study, a gene encoding the AATP protein, named Ib AATP, was isolated from sweetpotato(Ipomoea batatas(L.) Lam.). Transcripts of Ib AATP were predominantly detected in the storage roots and leaves and were induced by exogenous sucrose and subjected to circadian rhythm. Transient expression of Ib AATP in tobacco and onion epidermal cells revealed the plastidic localization of Ib AATP. The overexpression of Ib AATP in sweetpotato significantly increased the starch and amylose contents and led to enlarged starch granules. The IbA ATP-overexpressing plants showed altered fine structure of amylopectin, which contained an increased proportion of chains with a degree of polymerization(DP) of 10–23 and a reduced number of chains with a DP of 5–9 and 24–40. In addition, starch from the transgenic plants exhibited different pasting properties. The transcript levels of starch biosynthetic genes, including Ib AGP, Ib GBSSI, Ib SSIIV, and Ib SBE, were differentially regulated in the transgenic plants. These results revealed the explicit role of Ib AATP in the starch biosynthesis of sweetpotato and indicated that this gene has the potential to be used to improve starch content and quality in sweetpotato and other plants.
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