The gene structure of oryzacystatin-II, a new cystatin superfamily member of rice seed origin, was determined. In spans approximately 2.5 kbp the comprises 3 exons. The number of exons and the intron-breakpoints coincide with those of oryzacystatin-I, the first well-defined plant cystatin. However, no similar sequences were observed between the two oryzacystatin genes in 5′-upstream regulatory regions, even though both are expressed specifically during the ripening stage of rice seeds. The gene organization of these two plant cystatins is generally different from that of animal cystatins.
