Production and characterization of transgenic rice plants carrying a high-affinity nitrate transporter gene (OsNRT2.1)

Abstract

Enhancing nitrogen utilization is important in maintaining crop yield under low nitrogen conditions. Therefore, rice plants (Oryza sativa L.) were transformed with pMLH7133-RNRT2, which bears OsNRT2.1, a major gene involved in nitrate uptake under low nitrate concentrations. Two transgenic plants harboring an OsNRT2.1 transgene were identified and used for further study. In transgenic plants, OsNRT2.1 was expressed constitutively in roots, while in wild-type plants, the transcript was detected 30 min after starting to supply nitrate. No co-suppression between transgene and host gene was observed, as was observed on introduction of a nitrate reductase gene from the same species. One of the transformants grew faster than the wildtype cultivars when KNO3 or NH4NO3 was supplied as a nitrogen source. However, no increase in nitrate uptake by young plants was observed. These results suggest that constitutive expression of OsNRT2.1 might enhance vegetative growth and that introduction of genes involved in nitrate uptake from the same species may be useful for genetic improvement of plant growth under low nitrogen conditions. Further studies are necessary to understand the molecular and physiological bases of expression of NRT2.1 in relation to plant growth.