Physiological, Genome-Wide Characterization and Expression Analysis of Aquaporin Gene Family of Apocynum venetum in Response to Abiotic Stress

<b>Background:</b><i>Apocynum venetum</i> L., a saline-alkali-tolerant plant, is a valuable resource for forage, textile, and medicinal purposes. This study aimed to identify the AQP gene family in <i>A. venetum</i> genome-wide and explore their potential functions under abiotic stress. <b>Methods:</b> Gene identification, phylogenetic relationships, structural features, and evolutionary patterns were analyzed, along with gene expression patterns and correlations with physiological traits. <b>Results:</b> Phylogenetic analysis classified the 25 candidate AvAQP genes into five distinct subgroups, with members exhibiting conserved gene structures, motifs, and phosphorylation patterns. Subcellular localization predictions indicate targeting primarily to the plasma membrane or the vacuole, with one isoform (AvTIP5;1) predicted to localize to both. Synteny analysis revealed three intraspecific and multiple interspecific gene pairs (26 with <i>Arabidopsis thaliana</i> and 34 with <i>Medicago truncatula</i>). In silico promoter analysis identified 49 cis-regulatory elements associated with phytohormone response, stress signaling, and development, providing preliminary clues for their possible involvement in diverse biological processes. qPCR profiling under abiotic stress demonstrated tissue-specific expression patterns among AvAQP members under different stress conditions. Correlation analyses between gene expression and physiological indicators (growth- and water-related traits) were predominantly positive, with only a few negative correlations under stress conditions, suggesting that AvAQP expression may be associated with plant physiological status. <b>Conclusions:</b> This study presents a comprehensive analysis of the AQP family in <i>A. venetum</i> providing a foundation for further functional characterization of these genes in response to abiotic stress.