Isolation of MADS-box Genes from Sweet Potato (Ipomoea batatas (L.) Lam.) Expressed Specifically in Vegetative Tissues

New MADS-domain genes, IbMADS3 and IbMADS4, were isolated from pigmented and tuber-forming root tissue in sweet potato (Ipomoea batatas L.). Both genes were expressed preferentially in vegetative tissues, especially root tissues; white fibrous roots, pigmented roots, and developing tuberous roots. On sequence alignment, these genes fell into the STMADS group composed of SVP, STMADS11, STMADS16 and AGL24, which share high sequence similarity, similar expression patterns and similar function. Transcripts of these two genes in roots were found in the vascular cambium region. This particular expression pattern of these genes may lead to a higher proliferative potential of vegetative tissues, and may facilitate tuber initiation in sweet potato. These genes may lead to important information on the morphogenesis of vegetative structures.