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

Abstract

Nitrogen (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.

Dark septate endophytic fungi increase the activity of proton pumps, efficiency of 15N recovery from ammonium sulphate, N content, and micronutrient levels in rice plants

“…PCRs were performed to evaluate the expression of genes encoding six PM H + -ATPase isoforms (OsA1, OsA2, OsA3, OsA5, OsA7, and OsA8) previously detected in roots of rice plants [24], as well as to determine the expression of genes that codify NO 3 − transporters (OsNRT2.1 and OsNRT2.2) or the accessory protein OsNAR2.1. The sequences of the primers used to amplify cDNA from the PM H + -ATPases and the NRTs were described by Sperandio et al [24], while the primers used to amplify the OsNAR2.1 cDNA were described by Bucher et al [65]. The expression of elongation factor 1 [66] was used as an endogenous control in order to calculate the relative expression of the target genes by the 2 −ΔΔCT method [67].…”