Saussurea involucrata REVEILLE8, a circadian clock protein, confers salt tolerance by ROS signaling

Circadian rhythms are critical for plants to adjust growth and development in response to a fluctuating environment. Here, we report the functional characterization of SiRVE8, a circadian gene insolated from Saussurea involucrata, a plant that thrives in extreme environments. Expression pattern analysis revealed that SiRVE8 exhibits distinct circadian rhythmicity and is induced by salt stress and cold stress (4 °C). Functional verification using transgenic Arabidopsis and tomato consistently show that SiRVE8 positively regulates salt tolerance by reducing oxidative damage. Transcriptome analysis of transgenic Arabidopsis futher demonstrated that overexpression of SiRVE8 alters the expression of numerous stress-responsive genes, among which a large number are ROS-scavenging genes. Mechanistically, We confirm that SiRVE8 functions as a transcription activator that directly binds to the promoter of AtERF109 and upregulates its expression. Collectively, this findings establishes a SiRVE8-AtERF109-ROS regulatory module, which mitigates salt-induced oxidative damage and enhancing salt tolerance. This study not only provides new insights into the molecular mechanism by which the circadian clock component SiRVE8 mediates plant salt stress responses but also identifies SiRVE8 as a key candidate gene for genetic improvement of crop salt tolerance in the future.