Objective To identify the members of nitrate transporter (NPF) gene family in moso bamboo (Phyllostachys edulis) and systematically analyze their molecular characteristics and expression patterns, in order to lay the foundation for in-depth study of the nitrate transport function of the NPF genes in Moso bamboo.

Method Bioinformatics methods were used to identify NPF family gene members in the genome of Moso bamboo, a comprehensive analysis of acting elements in their promoters, gene structure, physical and chemical properties of their encoded proteins, conserved domains and systematic evolution was performed. The tissue specific expression of NPF genes in different tissues of Moso bamboo and their expression patterns after different abiotic stress and hormone treatments were analyzed using the existing transcriptome data.

Result A total of 27 NPF genes (PeNPF1.1~PeNPF8.8) were identified in Moso bamboo, and their gene structure was found to be quite different. The number of intron was 2~5. The longest coding region was 2286 bp (PeNPF7.4) and the shortest was 1359 bp (PeNPF8.8). The regulatory element analysis showed that a variety of elements related to abiotic stresses such as cold and drought, as well as hormonal responses such as GA₃ and NAA were identified in the promoter region of PeNPFs. The molecular weight of the proteins encoded by PeNPFs ranged from 49.56~82.08 kDa, with the isoelectric point (pI) of 5.17~9.85. Most PeNPFs were neutral or basic proteins with similar transmembrane structures. Phylogenetic analysis showed that PeNPFs were clustered into 7 subfamilies, and the numbers of members in each subfamily were 1, 3, 1, 6, 1, 7 and 8, respectively. Analysis of protein conserved motifs showed that there was a total of 10 conserved motifs in PeNPFs, of which motif 1, motif 2 and motif 4 were highly conserved motifs shared by all members. The expression profile heat map analysis based on transcriptome data demonstrated that the expression of PeNPFs had certain differences in different tissues such as leaves, inflorescences, roots, rhizomes and shoots, among which each member was detected in at least one tissue, and some members exhibited tissue-specific or constitutive expression. After cold and drought treatments, the expression of PeNPF5.3, PeNPF7.2, PeNPF7.3 and PeNPF8.7 showed significant down-regulation, which was consistent with the presence of cold and drought response regulatory elements in their promoter sequences. After GA₃ and NAA treatments, PeNPF7.3 and PeNPF7.6 demonstrated opposite expression changes, while the expression trend of PeNPF7.1 was similar.

Conclusion There are 27 members of NPF gene family in Moso bamboo, which can be divided into 7 subfamilies. The molecular characteristics and tissue expression specificity of each member in different subfamilies have certain differences, and the expression changes of some PeNPFs in response to abiotic stress and hormone treatments have reached the level of significant differences. These expression profiles suggest that PeNPFs might play different functions in the transport of nitrate in different tissues of bamboo and in the process of dealing with different environments. These findings could be references for understanding the biological functions of PeNPFs in Moso bamboo.