Genome-Wide Identification and Expression Analysis of NPF Genes in Cucumber ( Cucumis sativus L.).

The NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER family (NPF) proteins perform an essential role in regulating plant nitrate absorption and distribution and in improving plant nitrogen use efficiency. In this study, cucumber ( L.) genes were comprehensively analyzed at the whole genome level, and 54 genes were found to be unevenly distributed on seven chromosomes in the cucumber genome. The phylogenetic analysis showed that these genes could be divided into eight subfamilies. We renamed all genes according to the international nomenclature, based on their homology with genes. By surveying the expression profiles of genes in various tissues, we found that was specifically expressed in roots, indicating that may play a role in N absorption; was highly expressed in petioles, which may be related to NO storage in petioles; and was highly expressed in fruits, which may promote NO transport to the embryos. We further examined their expression patterns under different abiotic stress and nitrogen conditions, and found that and responded to salt, cold, and low nitrogen stress. Taken together, our study lays a foundation for further exploration of the molecular and physiological functions of cucumber nitrate transporters.