In-season expression of nitrate and ammonium transporter genes in roots of winter wheat (Triticum aestivum L.) genotypes with different nitrogen-uptake efficiencies

Abstract

Although nitrate and ammonium transporter genes of wheat have been cloned, little is known about their expression characteristics. A greenhouse experiment was established to study temporal expression patterns over a growing season for four nitrate-transporter genes (TaNRT2.1, TaNRT2.2, TaNRT2.3 and TaNRT1.2) and two ammonium-transporter genes (TaAMT1.1 and TaAMT1.2) in wheat genotypes with different nitrogen (N)-uptake efficiencies. Genotypes that were N-efficient (XY107) and N-inefficient (XY6) were planted in soils that were N-limited (no N added) and N-adequate (added 0.3 g N kg–1 soil). Roots were sampled at tillering, jointing, heading and grain-filling stages, and the expression of the six genes was quantified using real-time, reverse transcription PCR (polymerase chain reaction). Results indicated that maintaining active N uptake during reproduction was the main strategy used by genotype XY107 to sustain its high N-uptake efficiencies in both N treatments. The expression of all NRT and AMT genes showed significant temporal dynamics, and generally matched the pattern of in-season N uptake of wheat plants. Several NRT or AMT genes (especially TaNRT2.1) showed greater expression at reproduction in the N-efficient genotype, XY107, than in the N-inefficient genotype, XY6, suggesting that nitrate and ammonium transporters play important roles in determining the genotypic variation of N uptake in wheat.