Abstract：Nitrogen is one of the essential macronutrient for plants, thus nitrogen content in soil seriously affects plant growth and development. Nitrate as the most important source of nitrogen absorption for P. bournei and many other land plants, and the nitrate transporter/peptide transporter family (NRT/NPF) is involved in the nitrate uptake, transport and distribution. Therefore, the genome-wide identification and expression analysis of the NRT/NPF gene family are important for the studying of nitrogen uptake and utilization in P. bournei. In the present study, the genome-wide NRT/NPF genes of P. bournei were identified using NRT protein sequences of Arabidopsis thaliana and Hidden Markov Model (HMM) (PF00854, PF07690, PF16974), and 63 PbNRT/NPF members were identified, which were unevenly distributed on 11 chromosomes. The results showed that the molecular weights of PbNRT/NPF were 22.8~135.6 kD, isoelectric point were 5.44~9.41, encoding 205 to 1 235 aa. Most of the encoded proteins were basic proteins with 2~23 transmembrane domains, phylogenetic analysis revealed that 63 PbNRT/NPF genes could be divided into 3 subfamilies, of which 60 belonged to the NRT1/NPF subfamily, 2 to the NRT2 subfamily subfamily and 1 to the NRT3 subfamily. Collinearity analysis revealed that there were 9 tandem duplication events and 10 segmental duplication events in the PbNRT/NPF family. The transcriptome data and qRT-PCR analysis showed that PbNRT/NPF members were differentially expressed among 5 tissues of P. bournei, for example, PbNPF6.3 was significantly higher expressed in the root bark than that of other tissues. Furthermore, PbNRT/NPF members showed differential expression patterns under different low nitrogen treatments, e.g. the expression of PbNRT2.4 and PbNRT2.5 significantly increased under low nitrogen treatment. Overall, this study provides a basis for studying the functions of the PbNRT/NPF genes in nitrogen absorption, transport and utilization in P. bournei, and provides a theoretical basis for breeding and selection of low-nitrogen tolerant varieties in P. bournei.
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