Genome-wide identification and expression analysis of NIN-like protein (NLP) genes: Exploring their potential roles in nitrate response in tea plant (Camellia sinensis)

NIN-like proteins (NLPs) are evolutionarily conserved transcription factors that are unique to plants and play a pivotal role in responses to nitrate uptake and assimilation. However, a comprehensive analysis of NLP members in tea plants is lacking. The present study performed a genome-wide analysis and identified 33 NLP gene family members of Camellia sinensis that were distributed unequally across 5 chromosomes. Subcellular localisation predictions revealed that all CsNLP proteins were localised in the nucleus. Conservative domain analysis revealed that all of these proteins contained conserved RWP-RK and PB1 domains. Phylogenetic analysis grouped the CsNLP gene family into four clusters. The promoter regions of CsNLPs harboured cis-acting elements associated with plant hormones and abiotic stress responses. Expression profile analysis demonstrated that CsNLP8 was significantly upregulated in roots under nitrate stress conditions. Subcellular localisation analysis found CsNLP8 localised to the nucleus. Dual-luciferase reporter assay demonstrated that CsNLP8 positively regulated the expression of a nitrate transporter gene (CsNRT2.2). These findings provide a comprehensive characterisation of NLP genes in Camellia sinensis and offer insights into the biological function of CsNLP8 in regulating the response to nitrate-induced stress.