| Summary: | Thaxtomin A (TA) is a cellulose biosynthesis inhibitor synthesized by the soil actinobacterium <i>Streptomyces scabies</i>, which is the main causal agent of potato common scab. TA is essential for the induction of scab lesions on potato tubers. When added to <i>Arabidopsis thaliana</i> cell cultures, TA induces an atypical programmed cell death (PCD). Although production of reactive oxygen species (ROS) often correlates with the induction of PCD, we observed a decrease in ROS levels following TA treatment. We show that this decrease in ROS accumulation in TA-treated cells is not due to the activation of antioxidant enzymes. Moreover, <i>Arabidopsis</i> cell cultures treated with hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) prior to TA treatment had significantly fewer dead cells than cultures treated with TA alone. This suggests that H<sub>2</sub>O<sub>2</sub> induces biochemical or molecular changes in cell cultures that alleviate the activation of PCD by TA. Investigation of the cell wall mechanics using atomic force microscopy showed that H<sub>2</sub>O<sub>2</sub> treatment can prevent the decrease in cell wall rigidity observed after TA exposure. While we cannot exclude the possibility that H<sub>2</sub>O<sub>2</sub> may promote cell survival by altering the cellular redox environment or signaling pathways, our results suggest that H<sub>2</sub>O<sub>2</sub> may inhibit cell death, at least partially, by reinforcing the cell wall to prevent or compensate for damages induced by TA.
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