<i><scp>pOsNAR</scp>2.1:Os<scp>NAR</scp>2.1</i> expression enhances nitrogen uptake efficiency and grain yield in transgenic rice plants

Abstract

Summary The nitrate () transporter has been selected as an important gene maker in the process of environmental adoption in rice cultivars. In this work, we transferred another native Os NAR 2.1 promoter with driving Os NAR 2.1 gene into rice plants. The transgenic lines with exogenous pOsNAR 2.1:Os NAR 2.1 constructs showed enhanced Os NAR 2.1 expression level, compared with wild type ( WT ), and 15 N influx in roots increased 21%–32% in response to 0.2 m m and 2.5 m m and 1.25 m m 15 NH 4 15 NO 3 . Under these three N conditions, the biomass of the pOsNAR 2.1:Os NAR 2.1 transgenic lines increased 143%, 129% and 51%, and total N content increased 161%, 242% and 69%, respectively, compared to WT . Furthermore in field experiments we found the grain yield, agricultural nitrogen use efficiency ( ANUE ), and dry matter transfer of pOsNAR 2.1:Os NAR 2.1 plants increased by about 21%, 22% and 21%, compared to WT . We also compared the phenotypes of pOsNAR 2.1:Os NAR 2.1 and pOsNAR 2.1:Os NRT 2.1 transgenic lines in the field, found that postanthesis N uptake differed significantly between them, and in comparison with the WT . Postanthesis N uptake ( PANU ) increased approximately 39% and 85%, in the pOsNAR 2.1:Os NAR 2.1 and pOsNAR 2.1:Os NRT 2.1 transgenic lines, respectively, possibly because Os NRT 2.1 expression was less in the pOsNAR 2.1:Os NAR 2.1 lines than in the pOsNAR 2.1:Os NRT 2.1 lines during the late growth stage. These results show that rice NO 3 – uptake, yield and NUE were improved by increased OsNAR2.1 expression via its native promoter.