<i>AtR8</i> ncRNA mediates salt tolerance by regulating AtWRKY53– <i>AtABI3</i> modules and reactive oxygen species homeostasis in <i>Arabidopsis</i>

Salt stress causes ion toxicity and oxidation in plants, and severely restricts agricultural production, the regulatory network and detailed mechanisms of salt tolerance remain incompletely known. Many lncRNAs involved in stress responses have been identified in plants, most of which are transcribed by RNA polymerase II and respond to a single stress factor. Arabidopsis AtR8 is transcribed by RNA polymerase III, it responds to SA treatment and interacts with AtWRKY53/AtWRKY70 to affect root elongation. AtR8 also responds to light and ABA and together with AtABI3 and crucial genes for light signal affects hypocotyl elongation. In the present study, AtR8 expression was significantly inhibited under salt stress. Loss-of-function of AtR8 significantly reduced seed germination and seedling root growth under salt stress, the ability to maintain ROS homeostasis was weakened, and H2O2 tolerance was reduced. The AtWRKY53 and AtABI3 expression levels were simultaneously significantly increased in the atr8 mutants. The abi3 mutant showed strong salt tolerance. The AtWRKY53 directly binds to the W-box in the promoter region of AtABI3, and promotes AtABI3 expression. These results suggest that AtR8 affects the salt tolerance of Arabidopsis by regulating ROS homeostasis and AtWRKY53-mediated AtABI3 transcription. Identification of the AtR8/AtWRKY53/AtABI3 regulatory module contributes to elucidation of the molecular regulatory network of salt stress in plants. Elucidation of the functional diversity of AtR8 improves our understanding of the evolution and diversity of lncRNA mechanisms and molecular pathways involved in adaptation to different environments, which is important for the cultivation of stress-resistant cultivars.