Genome-Wide Identification, Expression Analysis, and Transcriptome Analysis of the NPF Gene Family under Various Nitrogen Conditions in Eucalyptus grandis

The NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER (NRT1/PTR) family (NPF) plays an important role in plant nitrate absorption, distribution, and nitrogen use efficiency. Nevertheless, few reports are available regarding Eucalyptus grandis NPF genes and their expression profiles. This study aims to identify and analyze NPF genes and their expression under various nitrogen (N) conditions. In this study, we successfully screened 64 NPF genes within the E. grandis genome. Subsequently, we conducted an extensive analysis, encompassing investigations into chromosome location, gene structure, phylogenetic relationship, promoter region, conserved motif, and gene expression profile. RNA-seq was conducted to analyze the expression profiles of EgNPF genes under different N conditions. The 64 NPF genes were categorized into eight distinct groups, exhibiting an uneven distribution among the 10 chromosomes of E. grandis, and no member was mapped on chromosome (Chr) 9. The examination of cis-regulatory elements revealed that NPF promoters were closely related to light responsive element, MeJA responsiveness, anaerobic induction, gibberellin responsiveness, low-temperature responsiveness, and auxin responsiveness. We used the comparative transcriptome method to identify the 10 differently expressed EgNPF genes of E. grandis under high-nitrogen (N: 119 mg/L) and low-nitrogen (N: 29.25 mg/L) conditions. Expression pattern analyses revealed that EUGRSUZ_G03119 showed an elevated expression in both leaves and roots under high-nitrogen conditions compared to low-nitrogen conditions, suggesting that EUGRSUZ_G03119 might affect nitrogen transport and redistribution, potentially boosting the stress tolerance of E. grandis in response to nitrogen deficiency. These findings may provide valuable insights into the evolutionary development of the NPF gene family in E. grandis and facilitate the clarification of the molecular mechanism underlying EgNPF-mediated N absorption and distribution in E. grandis.