Genome-Wide Identification and Expression Analysis of Adenylate Kinase Family Members in Pepper Under Abiotic Stress

Adenylate kinase (ADK), a highly conserved and ubiquitously expressed enzyme in plants, serves as a critical regulator of cellular energy homeostasis and abiotic stress adaptation. While <i>ADK</i> families have been characterized in model species (e.g., <i>Arabidopsis thaliana</i>, <i>Oryza sativa</i>) and crops such as tomato (<i>Solanum lycopersicum</i>), the molecular features and stress-responsive roles of <i>ADK</i> genes in pepper (<i>Capsicum annuum</i> L.) remain uncharacterized. Here, we systematically identified 15 <i>ADK</i> genes in pepper (named by chromosomal location) and revealed their evolutionary relationships with orthologs from four plant species, clustering into six conserved groups. The promoters of <i>CaADKs</i> were found to contain <i>cis</i>-acting elements linked to stress responses, including those responsive to abscisic acid, gibberellin, and low-temperature conditions. Tissue-specific expression profiling highlighted <i>CaADK9</i> as a ubiquitously expressed member, suggesting a housekeeping function in basal biological processes. Notably, functional assays under low-temperature and salt stress revealed distinct regulatory patterns: <i>CaADK11</i> and <i>CaADK12</i> were significantly downregulated, while <i>CaADK9</i> was upregulated under salt stress, indicating specialized roles in stress signaling. Additionally, we identified ADK-interacting partners involved in nucleotide homeostasis, providing novel insights into the molecular network underlying pepper's stress responses. This study represents the first comprehensive analysis of the <i>CaADK</i> family, laying a foundation for unraveling ADK-mediated stress adaptation mechanisms in Solanaceous crops.