Lack of glycolate oxidase1, but not glycolate oxidase2, attenuates the photorespiratory phenotype of catalase2-deficient Arabidopsis

摘要

The genes coding for the core metabolic enzymes of the photorespiratory pathway that allows plants with C3-type photosynthesisto survive in an oxygen-rich atmosphere, have been largely discovered in genetic screens aimed to isolate mutants that are unviableunder ambient air. As an exception, glycolate oxidase (GOX) mutants with a photorespiratory phenotype have not been describedyet in C3 species. Using Arabidopsis (Arabidopsis thaliana) mutants lacking the peroxisomal CATALASE2 (cat2-2) that displaystunted growth and cell death lesions under ambient air, we isolated a second-site loss-of-function mutation in GLYCOLATEOXIDASE1 (GOX1) that attenuated the photorespiratory phenotype of cat2-2. Interestingly, knocking out the nearly identical GOX2in the cat2-2 background did not affect the photorespiratory phenotype, indicating that GOX1 and GOX2 play distinct metabolicroles.We further investigated their individual functions in single gox1-1 and gox2-1 mutants and revealed that their phenotypes canbe modulated by environmental conditions that increase the metabolic flux through the photorespiratory pathway. High lightnegatively affected the photosynthetic performance and growth of both gox1-1 and gox2-1 mutants, but the negative consequencesof severe photorespiration were more pronounced in the absence of GOX1, which was accompanied with lesser ability to processglycolate. Taken together, our results point toward divergent functions of the two photorespiratory GOX isoforms in Arabidopsisand contribute to a better understanding of the photorespiratory pathway.