Nitrogen partitioning traits and expression patterns of N metabolism‐associated genes in maize hybrids with contrasting N utilization efficiencies

Abstract

AbstractThe nitrogen (N) uptake and utilization in maize (Zea mays L.) plants are accomplished through a series of biochemical reactions and transformations involving the N assimilation enzymes. Nitrate reductase (NR) and glutamine synthetase (GS) exert important functions in the N assimilation and remobilization processes. The mechanisms underlying plant N partitioning and the associated expression patterns of NR and GS genes in maize hybrids with different N utilization efficiencies were still not clear. In this study, the expression of ZmNR and ZmGS genes that are related to N partitioning were analyzed in two maize hybrids (XY335 and HN138). Results showed that XY335 displayed higher grain yield, kernel numbers, shoot N uptake, and physiological N utilization efficiency (NUtE) than those shown in HN138 under low‐N conditions. The higher post‐silking N uptake and N remobilization in vegetative organs in XY335 were associated with the enhanced net photosynthetic rate (Pn), the NR and GS activities in ear‐leaf. Additionally, the expression levels of ZmGS1.3 and ZmGS1.4 were up‐regulated when exposed to low‐N stress, showing higher values in XY335 than those in HN138. Correlation analysis showed that the expression levels of ZmNR, ZmGS1.3, and ZmGS1.4 are correlated with leaf NR and GS activities, N remobilization, and grain yield. Our investigation suggested the critical roles of the N metabolism‐associated genes in the modulation of internal N translocation and plant productivity in maize. Future transgene analysis on ZmNR and ZmGS can provide insights into the molecular mechanisms underlying plant tolerance to low N stress in maize.