NIN-like proteins in poplar play roles in responding to abiotic stresses and nitrate availability

• Total of 13 NLPs were identified in each 717 poplar haplotype. • NLPs in 717 poplar have undergone purifying selection. • Poplar NLP genes displayed variable patterns to NO 3 - availability. • Network analyses reveal the roles of poplar NLPs in C and N metabolism. • Poplar NLP10 and NLP11 might have a role in NO 3 - signaling. NIN-like proteins (NLPs) play crucial roles in NO 3 - signaling pathway, however, knowledge of NLPs in woody plants remains limited. A total of 13 NLP genes were identified in each haplotype of 717 poplar. All NLPs contained the PB1 and RWP-RK domains. Eight and nine duplicated gene pairs were detected for PtNLPs and PaNLPs , respectively. Promoter analysis of NLP genes in 717 poplar revealed the existence of many cis -elements of light and stress responses. The NLP genes exhibited distinct expression profiles across different tissues. For instance, NLP1 - NLP3 were nearly undetectable in leaves but highly accumulated in roots. The response of NLP genes to NO 3 - availability also showed complex patterns: NLP1, NLP3, NLP5, NLP10 and NLP11 , were induced by high NO₃⁻ availability in roots, but NLP6, NLP12 and NLP13 genes were inhibited by high NO 3 - conditions in both roots and leaves. Additionally, a protein interaction network centered around poplar NLP proteins was constructed, highlighting their potential roles in carbon and nitrogen (N) metabolism. These findings underscore the potential roles for poplar NLP genes in NO 3 - signaling and stress adaptation and lay a foundation for stimulating N use efficiency (NUE) in woody plants.