Overexpression of ADP-glucose pyrophosphorylase (IbAGPaseS) affects expression of carbohydrate regulated genes in sweet potato [Ipomoea batatas (L.) Lam. cv. Yulmi]

ADP-glucose pyrophosphorylase is crucial in starch metabolism. The open reading frame of IbAGPaseS gene is comprised of 1539-base pairs and encodes a polypeptide of 512 amino acid residues. The deduced IbAGPaseS protein sequence was homologous with that of other AGPase proteins of various plant species. Also, the IbAGPaseS gene appears to be a member of multiple gene families and further, the differences in the copy numbers among the ten cultivars were considered to lead to differences in starch contents. IbAGPaseS was expressed in whole tissues and revealed high activity in thick-pigmented roots and developing tuberous roots. RT-PCR analysis indicated that the main role of IbAGPaseS is starch biosynthesis accumulating sink tissues during sweet potato root development. The IbAGPaseS cDNA was introduced to sweet potato under the control of the CaMV 35S promoter using Agrobacterium-mediated gene transfer techniques, thereby affecting the expression levels of carbohydrate regulated genes and sporamin gene. These results suggest that IbAGPaseS affects carbohydrate gene regulation.