Deficiency of P5CS But Not PDH Decreases Proline Content and Raises the ROS Levels During Photo-Oxidative Stress in Arabidopsis thaliana Mutants
摘要
Proline accumulation in plants during environmental stress results from a balance between proline biosynthesis and proline oxidation. Pyrroline-5-carboxylate synthase (P5CS) and proline dehydrogenase (PDH) are crucial enzymes for proline biosynthesis and oxidation, respectively. We investigated the proline metabolism in Arabidopsis mutants, deficient in either proline biosynthesis (p5cs1-1, p5cs1-4) or proline oxidation (pdh1-2) enzymes. The leaves of wild-type or mutants were treated with methyl viologen (an oxidant) and exposed to dark, moderate (150 μmol photons m−2 s−1) or high light (600 μmol photons m−2 s−1) to create photo-oxidative stress. The p5cs mutants had much less proline and much more reactive oxygen species (ROS) than the pdh mutants under photo-oxidative stress conditions. In contrast, the deficiency in PDH did not affect proline accumulation during stress. We emphasise that P5CS is dominant over PDH in sustaining proline biosynthesis and optimising leaves’ redox status under photo-oxidative stress.