Tran, Lan T.Mottiar, YaseenIrwin, TylerEfe, MahinurRobbins, SamanthaHawkins, Barbara J.Mansfield, Shawn D.Ehlting, Jürgen2026-06-222026-06-222026Tran, L. T., Mottiar, Y., Irwin, T., Efe, M., Robbins, S., Hawkins, B. J., Mansfield, S. D., & Ehlting, J. (2026). A nitrate transporter 1/peptide transporter family gene impacts nitrogen homeostasis and phenylpropanoid production in hybrid poplar. Journal of Experimental Botany, 77(5), 1483–1493. https://doi.org/10.1093/jxb/erag034https://doi.org/10.1093/jxb/erag034https://hdl.handle.net/1828/24006In plants, nitrogen and carbon metabolism are tightly interconnected, and nitrogen availability often negatively correlates with phenylpropanoids that are associated with xylem formation and stress responses. A nitrate transporter 1/peptide transporter (NRT1/PTR) family (NPF) gene (PtNPF6.1), which is expressed in the vasculature, was previously found to have a genetic association with the variation in syringyl lignin content in poplar trees (Populus trichocarpa). PtNPF6.1 belongs to an evolutionarily distinct NPF superfamily with limited taxonomic distribution. RNAi-mediated suppression of PtNPF6.1 led to increases in total foliar nitrogen and amino acids related to nitrogen transport and storage in source leaves. There was also a concomitant decrease in soluble phenolics, including attenuated stress-induced production of anthocyanins and condensed tannins. The proportions of syringyl and p-hydroxyphenyl units in lignin were slightly but significantly decreased in down-regulated lines grown under high nitrogen conditions, while there was an increase in the level of ester-linked p-hydroxybenzoate groups. Together, these results suggest that PtNPF6.1 is involved in maintaining internal nitrogen homeostasis in trees, indirectly impacting the production of nitrogen-free phenolics including lignin and soluble secondary metabolites.enAttribution-NonCommercial 4.0 Internationalamino acidsfertilizationhigh lightligninnitratenitrogen transportpeptidephenolicsphenylpropanoidspoplarCentre for Forest BiologyArticleDepartment of Biology