Comparative analysis of nitrogen metabolism-related genes in two inbred maize lines with different low-nitrogen tolerance

Abstract

Maize is an important crop and its nitrogen use efficiency (NUE) has been an issue for plant scientists and breeders for many years. To meet the demand of genetic diversity in cultivating local elite maize cultivars, researchers need to isolate germplasms with a high NUE. In this study, 30 maize inbred lines were screened under hydroponic conditions, and three inbred lines that tolerate low nitrogen concentration were identified. A comparative analysis of genes involved in N uptake, transport, and assimilation between two lines with different tolerances revealed that the low-nitrogen-tolerant inbred line MBST exhibited higher expressions of nitrate and ammonium transporters, especially ZmNRT3.1B, than less tolerant B73. This suggests that the MBST line had a more efficient high-affinity transporter system. We also showed that lownitrogen conditions down-regulated the expressions of master genes, ZmNLPs, which were negatively correlated with the expressions of the nitrate transporters ZmNRTs. This indicates the existence of regulators that antagonize the function of ZmNLPs. Some genes related to N assimilation and carbon metabolism were also more expressed in MBST. This research shows that the low-nitrogen-tolerant line, MBST, transported nitrate and ammonium more effectively than the B73 line. The NUE was also higher in MBST than in B73.