Physiological And Molecular Mechanism Of Difference Of Nitrogen Use Efficiency Among Winter Wheat Genotypes

A pot experiment was established to study the seasonal changes of the genotypicvariations of wheat in nitrogen (N) uptake and utilization efficiencies, and to studyphysiological and molecular mechanism of variation of NUE. Six wheat cultivars (LM1,ZM9023, YM18, XY22, XY6and XY107) were cultured in soils with two N fertilizertreatments, low N(0g N/kg soil) and high N(0.3N/kg soil). Wheat shoot and root sampleswere taken at the tillering, jointing, heading, grain filling and maturity stages. The mainresults and conclusions as follows:1、In the low N treatment, LM1had the highest uptake efficiency and XY6had thelowest uptake efficiency. In the high N treatment, both XY107and YM18had the highestuptake efficiency and XY6had the lowest uptake efficiency. YM18and LM1had the highestutilization efficiency in LN and HN, respectively. Both LM1and XY6had the lowestutilization efficiency in the low N treatment and XY6had the lowest utilization efficiency inthe high N treatment. The differences of the cultivars in NUpE and NUtE mainly occurredafter grain filling stage.2、The expression of all NRT and AMT genes showed significant seasonal dynamicsin both N-efficient wheat genotype(XY107) and N-inefficient wheat genotype(XY6). Theseasonality in gene expression corresponded with typical patterns of N uptake by wheat plants,suggesting that nitrate and ammonium transporters play important roles in regulating Nuptake. Maintaining active N uptake in roots after the heading stage in the N-efficient wheatgenotype appeared to be an important strategy for keeping its high efficiency in N uptake, andall NRT and AMT genes contributed to this strategy. We suggest that the combination ofmultiple nitrate and ammonium transporters determine the genotypic variation of N uptake inwheat. The gene TaNRT2.1may be the most important in determining the genetic variation ofwheat in N uptake compared with other NRT or AMT genes.3、The higher grain NUtE in the N-efficient wheat genotype YM18appears mainlyto be due to the higher N remobilization efficiency of YM18compared to the N-inefficientgenotype XY6. The expression of the genes TaGS1and TaPPDK in YM18was significantlygreater than that in XY6at the reproductive growth stages in both low and high N treatments, which may contribute significantly to the high N remobilization efficiency of YM18. Theexpression level of TaAlaAT in YM18was also significant higher than that in XY6at thereproductive growth stages, but only occurred in N-limited condition. The present studysupports the genes TaGS1, TaAlaAT and TaPPDK as potential targets to enhance NUtE ofwheat.