We isolated transformation-competent artificial chromosome (TAC) clones harboring a high-molecularweight glutenin subunit (HMW-GS) gene and a low-molecular-weight GS (LMW-GS) gene from wheat genomic DNA, and developed transgenic rice lines with these genes using a transformation system mediated by Agrobacterium tumefaciens. We developed two lines of transgenic rice, one expressing the gene coding for HMW-GS and the other expressing the gene coding for LMW-GS. By crossing these transgenic lines, a novel line harboring both genes was developed and the expression of GS proteins was analyzed. This is the first study indicating that the two kinds of wheat GSs, HMW-GS and LMW-GS, accumulated in rice endosperm. In all the transgenic lines, the introduced GS genes were expressed in the rice endosperm, and the expressed proteins were processed at the same site as the mature GS protein in wheat seeds, forming insoluble polymeric proteins similar to those found in wheat. It was suggested that the protein-processing system was conserved between rice and wheat, and that it was possible to produce wheat gluten using the proteinprocessing system of rice.