Exploring the regulatory roles of AtGLR3.4 receptors in mitochondrial stress and ROS management in Arabidopsis.

Key message: atglr3.4.1 knockout disrupts H₂O₂-scavenging enzymes, increasing ROS and redox imbalance. This upregulates COX5B, UPOX, and UCP. AtGLR3.4.2 maintains redox homeostasis, highlighting AtGLR3.4 receptors' role in mitochondrial stress. Glutamate receptors (iGluRs/mGluRs) play a crucial role in cognitive processes in mammals. Studies in humans have shown that the overexpression of glutamate receptors increases Ca²⁺ influx into the cell, leading to nitric oxide (NO) accumulation, which in turn induces mitochondrial stress. Dysregulated activity of (iGluRs/mGluRs) is linked to depression, psychosis, and neurodegenerative diseases in humans. In plants, GLRs are involved in carbon and nitrogen metabolism and seed germination. Research in Arabidopsis has shown that GLRs play a key role in generating and responding to stress signals. However, it remains unknown how GLR-mediated changes in NO levels affect mitochondria in plants. To address this question, our study investigated the effects of AtGLR3.4.1 and AtGLR3.4.2 receptors on mitochondrial stress under nitrosative stress conditions. For this purpose, we used A. thaliana wild type and atglr3.4 mutants (atglr3.4.1 and atglr3.4.2). To induce mitochondrial stress, we applied 80 µM Complex I inhibitor Rotenone. We examined the accumulation of reactive oxygen/nitrogen species (ROS/RNS), the effectiveness of the antioxidants responsible for their scavenging, cellular redox balance, and the expression of mitochondrial stress-related genes. The absence of AtGLR3.4.1 increased ROS accumulation by inhibiting catalase (CAT) and ascorbate peroxidase (APX) and disrupting the GSH/GSSG and NAD/NADH ratios. In atglr3.4.2 mutants, ROS-related oxidative damage was regulated by the ascorbate-glutathione cycle. atglr3.4.1 knockout increases the transcription of stress-related genes (COX5B, UPOX, and UCP), highlighting its role in oxidative stress management. These findings highlight AtGLR3.4 is crucial for preventing excessive ROS and redox homeostasis under mitochondrial stress responses.