Abstract
Zinc (Zn) is an essential element for humans as well as for plants. Sweet potato is a major staple crop in the world, and is an attractive target crop for genetic engineering because its suitability for clonal propagation and its self-incompatibility. OsZIP4 is a rice Zn transporter that increases Zn concentrations, especially in roots, when it is artificially overexpressed in rice. In our study we induced an embryogenic callus from the apex of sweet potato (Ipomoea batatas L. Lam. cv. Kokei No. 14), and obtained OsZIP4 overexpressed lines driven by the CaMV35S promoter through Agrobacterium infection. Three transgenic lines were confirmed by RT-PCR for their OsZIP4 expression in roots and leaves. Zn concentrations in roots and leaves of OsZIP4 transgenic plants grown on LS medium were approximately 2.3 times and 1.3 times higher, respectively than those of wild type plants. In addition, the iron content of tubers was two times higher than wild type (WT) lines, and that of leaves was up to 1.2 times higher. Root tubers of transgenic lines were obtained under soil culture. The Zn concentration of transgenic sweet potato tubers was 2.2 times higher than WT lines, but there were no differences in shoot length or fresh weight between the transgenic and WT lines. These results indicate that introducing the OsZIP4 gene in to sweet potato is a potential method to improve the Zn nutrition of livestock and humans.
