Lack of GLYCOLATE OXIDASE 1, but not GLYCOLATE OXIDASE 2, attenuates the photorespiratory phenotype of CATALASE2-deficient Arabidopsis
The genes coding for the core metabolic enzymes of the photorespiratory pathway, which allows plants with C3-type photosynthesis to survive in oxygen-rich atmosphere, have been largely discovered in genetic screens aimed to isolate mutants that are unviable under ambient air. As an exception, glycolate oxidase (GOX) mutants with a photorespiratory phenotype have not been described yet in C3 species. Using Arabidopsis mutants lacking the peroxisomal CATALASE 2 (cat2-2) that display stunted growth and cell death lesions under ambient air, we isolated a second-site loss-of-function mutation in GLYCOLATE OXIDASE 1 that attenuated the photorespiratory phenotype of cat2-2. Interestingly, knocking out the nearly identical GLYCOLATE OXIDASE 2 in the cat2-2 background did not affect the photorespiratory phenotype, indicating that GOX1 and GOX2 play distinct metabolic roles. We further investigated their individual functions in single gox1-1 and gox2-1 mutants and revealed that their phenotypes can be modulated by environmental conditions that increase the metabolic flux through the photorespiratory pathway. High light negatively affected the photosynthetic performance and growth of both gox1-1 and gox2-1 mutants, but the negative consequences of severe photorespiration were more pronounced in the absence of GOX1 which was accompanied with lesser ability to process glycolate. Taken together, our results point toward divergent functions of the two photorespiratory GOX isoforms in Arabidopsis and contribute to a better understanding of the photorespiratory pathway.
Kerchev, P.I., Waszczak, C., Lewandowska, A., Willems, A., Shapiguzov, A., Li, Z., Alseekh, S., Mühlenbock, P., Hoebrichts, F., Huang, J., Van Der Kelen, K., Kangasjarvi, J., Fernie, A., De Smet, R., Van de Peer, Y., Messens, W., Van Breusegem, F. (2016) Lack of GLYCOLATE OXIDASE 1, but not GLYCOLATE OXIDASE 2, attenuates the photorespiratory phenotype of CATALASE2-deficient Arabidopsis. Plant Physiol. (In Press).
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