Identification of Grape <i>NRT</i> Gene Family and Analysis of Its Expression in Leaves Under Nitrogen-Deficiency Stress

Nitrogen, an indispensable macronutrient, significantly affects the appearance, quality, and yield of grapes (<i>Vitis vinifera</i>). Adequate nitrate uptake and intracellular transport, facilitated primarily by nitrate transport (NRT) proteins, are crucial for maintaining nutritional balance. However, there are no reports on the <i>NRT</i> gene family in grapes. In this study, we identified 53 <i>Nitrate Transporter 1/Peptide Transporter Family</i> (<i>NPF</i>), 3 <i>nitrate transporter 2 family</i> (<i>NRT2</i>), and 1 <i>Nitrate Assimilation-Related 2</i> (<i>NAR2</i>) genes in the grapevine Pinot Noir PN40024 genome. A comprehensive analysis of these gene families, including their physicochemical properties, structural organization, chromosomal distribution, collinearity, cis-acting element distribution, and phylogenetic relationships, revealed the rich diversity and evolutionary conservation of the grapevine <i>Nitrate Transporter</i> (<i>NRT</i>) <i>genes</i>. Furthermore, the expression profiles of <i>VvNRTs</i> in different tissues demonstrated that the <i>NRT</i> genes possess spatio-temporal expression specificity. The expression patterns of the <i>NRT</i> genes were examined by transcriptome sequencing in grapevines across various tissues under nitrogen-deficiency conditions. The expression patterns in grapevine leaves under nitrogen-deficiency conditions showed upregulation of the <i>VvNPF2.3</i> gene in conditions of nitrogen deficiency. This upregulation was strongly associated with a 62.2% reduction in indole-3-acetic acid (IAA) levels and a 21.3% increase in hydrogen peroxide (H₂O₂) levels, suggesting a complex regulatory response to nitrogen-induced stress. These findings emphasize the potential involvement of <i>NRT</i> genes in the adaptive reaction to nitrogen deficiency and set the stage for future investigations into the molecular mechanisms of nitrogen transportation in grapevines.