The Circadian Oscillator Affects Both Glutathione Homeostasis and Its Response to Salt Stress in Arabidopsis thaliana

Apr 19, 2026Plant, cell & environment

The Plant's Internal Clock Influences Antioxidant Balance and Its Reaction to Salt Stress in Arabidopsis

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Abstract

Diurnal oscillations in glutathione levels are observed, yet GSH content is not regulated by the circadian oscillator.

GSSG levels and glutathione reductase (GR) gene expression and activity are influenced by the circadian oscillator.
Transcript levels related to glutathione biosynthesis and degradation exhibit diurnal rhythms.
The circadian clock is associated with the modulation of glutathione homeostasis through GR activity.
CCA1-ox plants show a diminished GR response to saline stress, indicating a potential role of the circadian oscillator in glutathione response to salinity.

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Glutathione, including reduced glutathione (GSH) and oxidized glutathione (GSSG), is the major non-protein thiol-based redox buffer. There are diurnal rhythms in total glutathione level and in this work, we investigate whether these oscillations might be indicative of circadian regulation of total glutathione homeostasis. We have not only taken a look and determined transcript levels involved in glutathione homeostasis, but we have also measured GSH and GSSG levels, and glutathione reductase (GR) activity in both wild-type plants and plants that constitutively express CIRCADIAN CLOCK ASSOCIATE1 (CCA1-ox), under diurnal and circadian cycles, and under stress saline conditions. In spite of the presence of diurnal oscillations in several genes involved in glutathione biosynthesis and degradation and in GSH levels, GSH content does not appear to be regulated by the circadian oscillator as shown by the data in CCA1-ox plants. Unlike GSH, we report that GSSG levels and GR gene expression and activity are affected by alterations in the circadian oscillator, demonstrating that Arabidopsis circadian clock modulates the homeostasis of glutathione via GR. Additionally, we show that GR response to saline stress is lack in CCA1-ox plants, suggesting that the oscillator regulates glutathione response to salinity.

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The Circadian Oscillator Affects Both Glutathione Homeostasis and Its Response to Salt Stress in Arabidopsis thaliana

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