Integrative Analysis of Mitochondrial Dysfunction and Stress Signaling in Arabidopsis Roots Exposed to Salinity
Keywords:
Salt Stress, Mitochondria, Alternative Oxidase, Oxidative Phosphorylation, ROS, Arabidopsis Thaliana, Bioenergetics, UPRmtAbstract
Salt stress poses a major limitation to plant growth, particularly affecting root energy metabolism and redox stability. This study investigates how mitochondrial bioenergetics in Arabidopsis root cells are reprogrammed in response to moderate and severe salt stress. Using high-resolution respirometry and transcriptomic profiling, we assessed mitochondrial performance under 0, 100, and 200 mM NaCl. Mitochondrial respiration was measured using the O2k Oroboros system, applying a substrate-uncoupler-inhibitor titration protocol. Key parameters included basal, OXPHOS, LEAK respiration, respiratory control ratio (RCR), ATP production, and maximal electron transport capacity. RNA-seq followed by qPCR validation was conducted to evaluate gene expression changes. Physiological markers such as ROS, proline, malondialdehyde (MDA), and K⁺/Na⁺ ratios were also quantified. Results showed a substantial decline in OXPHOS (up to 60%) and ATP production (up to 70%) under 200 mM NaCl, alongside a marked increase in LEAK respiration and ROS emission. RCR values dropped from 7.2 to 2.1, indicating impaired mitochondrial efficiency. AOX1a expression increased 8-fold, while Complex I genes were downregulated. Concurrently, proline levels rose 15-fold, and MDA and ROS levels confirmed oxidative stress. Transcriptomic data revealed activation of antioxidant pathways and UPRmt components. These findings reveal a coordinated mitochondrial adaptation under salt stress, shifting electron transport from canonical pathways toward AOX-mediated respiration to maintain redox balance. The integration of bioenergetic, molecular, and physiological data provides novel insights into the mechanisms underlying stress tolerance. Targeting AOX and mitochondrial stress responses may enhance resilience in crops facing increasing salinity.
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