Activation of ascorbate metabolism by nitrogen starvation and its physiological impacts in Arabidopsis thaliana

Redox homeostasis is crucial for plant acclimation to nutrient-deficient conditions, but its molecular mechanisms remain largely unknown. In this study, the effects of nutrient deficiencies on antioxidant systems in Arabidopsis thaliana were investigated. We found that ascorbate content in the plants grown with nitrogen starvation was higher than those with complete nutrition. The higher ascorbate levels were associated with enhanced gene expression of ascorbate biosynthesis enzymes and cytosolic isozymes of the ascorbate-glutathione cycle, suggesting that nitrogen starvation facilitated both consumption and biosynthesis of ascorbate. Nevertheless, we did not identify any phenotypic differences between wild type and ascorbate-deficient mutants (vtc2) under nitrogen starvation. Under high-light stress, the vtc2 mutants suffered severer photoinhibition than wild type. Interestingly, when high-light stress and nitrogen starvation were combined, wild type and vtc2 plants exhibited photoinhibition to the same extent. Based on these findings, we discuss the regulation and role of ascorbate metabolism under nitrogen starvation.

Automated summary

Redox homeostasis is crucial for plant acclimation to nutrient-deficient conditions. This study investigated the effects of nutrient deficiencies on antioxidant systems in Arabidopsis thaliana and found that nitrogen starvation increased ascorbate content. However, there were no phenotypic differences between wild type and ascorbate-deficient mutants under nitrogen starvation. Under high-light stress, the mutants experienced more severe photoinhibition than the wild type, but the same extent of photoinhibition was observed for both wild type and mutants when high-light stress and nitrogen starvation were combined.