Genome-wide identification of aldehyde dhydrogenase (ALDH) family genes in pepper (Capsicum annuum) reveals involvement of CaALDH7B1 in heat and drought stress tolerance

Abiotic stresses such as heat and drought lead to oxidative damage in plants by inducing excessive accumulation of reactive oxygen species (ROS). Aldehyde dehydrogenases (ALDHs), which detoxify reactive aldehydes, play critical roles in stress responses, but their functions in pepper (Capsicum annuum) remain largely unexplored. In this study, 28 CaALDH genes were identified and categorized into nine families. Phylogenetic and synteny analyses revealed strong evolutionary conservation, highlighting CaALDH2B4 and CaALDH7B1 as key members. Expression profiling showed distinct tissue-specific patterns and robust induction under heat and drought stress. Functional analysis via virus-induced gene silencing (VIGS) confirmed that CaALDH7B1 enhances stress tolerance by limiting ROS accumulation, promoting antioxidant enzyme activity (SOD, CAT, APX, POD), and maintaining NADPH/NADP⁺ homeostasis. Comparative genomics and structural modeling further revealed that CaALDH7B1 is evolutionarily conserved, with critical NADP⁺-binding residues retained across plant species. These findings underscore the pivotal role of CaALDH7B1 in oxidative stress regulation and provide new insights into the functional evolution of the ALDH gene family in pepper.