Genome-wide identification of ADK gene family associated with heat stress tolerance in chili (Capsicum annuum L.)

Chili (Capsicum annuum), also known as hot pepper, is a major vegetable crop in the Solanaceae family. It originated from C. annuum var. minimum, native to Mexico, Southern Peru, and Bolivia. High temperatures negatively affect all key development stages of chili, including fruit set, pollen viability, floral aberration, and the number of seeds per fruit. Heat stress tolerance is a crucial trait in chili and may be regulated by the Adenylate Kinase (ADK) gene family. Although ADK genes have been studied in Arabidopsis thaliana, Oryza sativa, Glycine max, Solanum lycopersicum, and Solanum tuberosum, they remain uncharacterized in C. annuum. This study presents the first genome-wide analysis of the ADK gene family in chili, including gene identification, phylogenetics, motif analysis, expression profiling, and stress-related interaction networks. This study identified nine ADK genes in C. annuum and 70 orthologs from four other species using BLASTp. Phylogenetic analysis grouped the genes into four clades, while gene structure analysis revealed gene lengths ranging from 1,204 to 13,304 bp, with 4 to 17 exons. Conserved motifs and ADK domains were identified. Chromosomal mapping placed the genes across nine chromosomes, with segmental duplications aiding expansion. Predicted subcellular localization suggested that most CaADK proteins localize to chloroplasts and mitochondria. In silico expression profiling showed that CaADK1 and CaADK8 had the highest expression under heat stress, indicating their potential role in thermotolerance. These findings provide novel insights into the CDK gene family in chili and offer molecular targets for enhancing heat stress tolerance in C. annuum.