Jointed physiological, transcriptome and genetic analysis reveals the molecular mechanism of nitrogen remobilization during leaf senescence process in maize

Based on three stages transcriptome analysis after silking, we identified 9,187 differentially expressed genes (DEGs) between two parental lines and a major change in transcriptional activity was observed at 25 DAS. Functional annotation showed that up-regulated genes in PH4CV at 25DAS were mainly enriched in intracellular protein transport. Whereas up-regulated genes in PH6WC at 25DAS were involved in photosynthesis process. Using weighted gene co-expression network analysis (WGCNA) and correlation analysis with phenotype, we identified eight co-expression modules and two of them were highly positive correlated with NRE. From the two NR related modules, we found that some hub genes, hormones, signaling genes and transcription factors work together playing a crucial part in NR process. After that, we use a F1-DH segregation populations deriving from two parents, and mapping one major effect QTL with NR trait named qNT5.04. By integrating transcriptomic related with the NR phenotypic variance, we predicted two core candidate genes (GRMZM2G057841 and GRMZM2G172230) may be involved in NR process in QTL region. The functions were participating in regulatory protein degradation and it is possible to be the target gene for engineering NR in maize. Finally, we constructed a molecular regulatory network of NR process in maize using candidate genes in QTL region and parental DEGs which is associated with NR.