Engineering of hypotensive rice to contain high amounts of nicotianamine for functional foods

摘要

Nicotianamine (NA), a chelator of metals, is ubiquitously present in higher plants. NA plays several roles in plants, all relating to the allocation of transition metals in plant cells and organs. In graminaceous plants, NA is an intermediate in the biosynthesis of mugineic acid family phytosiderophores, which are crucial chelators for Fe acquisition from the soil. A number of NA synthase (NAS) genes have been isolated from various plants. NA inhibits the angiotensin I-converting enzyme (ACE), and consequently may function in reducing high blood pressure. Therefore, it is likely that foods with high amounts of NA are beneficial to human health, and could be considered functional foods. Here, we aimed to engineer hypotensive rice with high amounts of NA in the grain by introducing the NAS gene from barley (HvNAS1). The expression of HvNAS1 was driven by the rice glutelin promoter. By using this promoter, HvNAS1 is expressed in the edible part of the rice grain, and consequently, NA may accumulate there. In addition, we generated 'marker-free hypotensive rice' by using a marker-free vector. The grains of transgenic rice contained four times more NA than non-transgenic rice did. In addition, the selection marker (antibiotic-resistant genes) could be removed by chemical induction.