Divergent Molecular Responses to Heavy Water in Arabidopsis thaliana Compared to Bacteria and Yeast

Heavy water (D₂O) is scarce in nature, and despite its physical similarity to water, D₂O disrupts cellular function due to the isotope effect. While microbes can survive in nearly pure D₂O, eukaryotes such as <i>Arabidopsis thaliana</i> are more sensitive and are unable to survive higher concentrations of D₂O. To explore the underlying molecular mechanisms for these differences, we conducted a comparative proteomic analysis of <i>E. coli</i>, <i>S. cerevisiae</i>, and <i>Arabidopsis</i> after 180 min of growth in a D₂O-supplemented media. Shared adaptive mechanisms across these species were identified, including changes in ribosomal protein abundances, accumulation of chaperones, and altered metabolism of polyamines and amino acids. However, <i>Arabidopsis</i> exhibited unique vulnerabilities, such as a muted stress response, lack of rapid activation of reactive oxygen species metabolism, and depletion of stress phytohormone abscisic acid signaling components. Experiments with mutants show that modulating the HSP70 pool composition may promote D₂O resilience. Additionally, <i>Arabidopsis</i> rapidly incorporated deuterium into sucrose, indicating that photosynthesis facilitates deuterium intake. These findings provide valuable insights into the molecular mechanisms that dictate differential tolerance to D₂O across species and lay the groundwork for further studies on the biological effects of uncommon isotopes, with potential implications for biotechnology and environmental science.