ThASR4 enhances salt tolerances in transgenic Tamarix and Arabidopsis by Scavenging Reactive Oxygen Species

Abstract ASR genes are a class of genes that are expressed in plants in response to abscisic acid, abiotic stress, and fruit ripening. While they have been cloned and functionally characterized in various plant species, their study in Tamarix hispida has been limited. In this study, six ThASR genes were cloned from Tamarix hispida . Expression analysis revealed that ThASR genes respond to salt stress. Specifically, ThASR4 was found to be highly induced in both shoots and root of Tamarix hispida under salt stress, thus prompting its selection for further functional characterization in salt stress responses. ThASR4 is targeted to the nucleus and possesses transcriptional activity. Under salt stress conditions, compared with the wild-type (WT) lines, ThASR4 -overexpressing Arabidopsis thaliana exhibited enhanced germination rate, longer primary roots, and higher fresh weight, indicating a marked improvement in salt tolerance. Correspondingly, both ThASR4 -overexpressing T. hispida and A. thaliana plants exhibited significantly diminished levels of reactive oxygen species (ROS), malondialdehyde (MDA), and electrolyte leakage, along with elevated activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), as well as increased proline (Pro) content, compared to Control plants. In contrast, ThASR4 RNA interference (RNAi) transgenic T. hispida displayed the opposite phenotypic and physiological outcomes. Furthermore, ThASR4 was found to upregulate the expression of ROS scavenger-associated genes ( ThPOD1, ThSOD1 and ThCAT3 ) and salt Stress-Responsive genes ( ThSOS3 , ThPIP2;5 , and ThDREB ). Collectively, our results indicate that ThASR4 enhances salt tolerance in T. hispida and A. thaliana by improving ROS scavenging capacity. The present study provides a theoretical foundation for further investigation into the regulatory mechanism of ThASR4 in the salt stress adaptation of T. hispida .