The transcription of nitrate transporters in upland rice varieties with contrasting nitrate‐uptake kinetics

Abstract

AbstractNitrogen (N) is one of the mineral elements required in the greatest quantity by plants and the one that most often limits productivity. In addition, the use of N fertilizers may be associated with environmental damage. The rational use of N fertilizers can be achieved by both better management techniques and the use of plant varieties that are more efficient in N use. Two rice (Oryza sativa L.) varieties (Piauí and IAC‐47) with contrasting nitrate‐uptake kinetics (Km and Vmax) were studied through the evaluation of the transcription of genes encoding for the high and low‐affinity nitrate transporters (NRT2 and NRT1, respectively) and NAR2 partner protein needed for NRT2 functional nitrate transporter, as well as the assessment of N soluble fractions (amino‐N, NO$ _3^- $‐N, NH$ _4^+ $‐N) and soluble sugars. The Piauí variety presented higher transcription of the OsNAR2.1, OsNRT2.1, OsNRT2.2 and OsNRT2.3a and accumulated more NO$ _3^- $ in the shoots, sheath and roots when cultivated under low supply of nitrate. OsNRT2.1, OsNRT2.2 and OsNAR2.1 transcription correlated with nitrate concentration in roots, while OsNRT2.1, OsNRT2.2 and OsNRT2.3a correlated with nitrate concentration in leaves. The results of this study indicate that the Piauí variety is adapted to conditions of low natural fertility and seasonal nitrate flux, characteristics of the humid tropics. There is evidence that a portion of this adaptation process maybe due to the differential expression of genes encoding for the high‐affinity nitrate transport proteins, synchronizing plant metabolism with nitrate availability in the soil.