Identification of the ASR gene family from Brachypodium distachyon and functional characterization of BdASR1 in response to drought stress.

KEY MESSAGE: A genome-wide investigation identified five B. distachyon ASR genes. BdASR1 may be a transcription factor that confers drought resistance by activating antioxidant systems involving ROS-scavenging enzymes and non-enzymatic antioxidants. Abscisic acid-, stress-, and ripening-induced (ASR) proteins belong to a family of plant-specific, small, and hydrophilic proteins with important roles in responses to abiotic stresses. Although several ASR genes involved in drought tolerance have been characterized in various plant species, the mechanisms regulating ASR activities are still uncharacterized. Additionally, no research on Brachypodium distachyon ASR proteins have been completed. In this study, five B. distachyon BdASR genes were identified through genome-wide analyses. Phylogenetic analyses revealed that BdASR genes originated from tandem and whole genome duplications. Expression analyses revealed the BdASR genes responded to various abiotic stresses, including cold, drought, and salinity, as well as signaling molecules such as abscisic acid, ethylene, and H2O2. BdASR1, which localizes to the nucleus and is transcriptionally active, was functionally characterized. BdASR1 overexpression considerably enhanced drought tolerance in transgenic tobacco plants, which was accompanied by increased superoxide dismutase, catalase, and peroxidase activities, as well as an increased abundance of antioxidants such as ascorbate, tocopherols, and glutathione. BdASR1 may function as a transcription factor that provides drought stress resistance by inducing the production of reactive oxygen species-scavenging enzymes and non-enzymatic antioxidants.