biostudies-literatureCaccamo AResearch Foundation Flanders—Fonds de la Recherche Scientifique Excellence of ScienceResearch Foundation Flanders-Fonds de la Recherche Scientifique Excellence of ScienceVIBFonds de la Recherche Scientifique -FNRS644-656https://www.ebi.ac.uk/biostudies/studies/S-EPMC11094752biostudies-literatureUnknown65(4)The function of ascorbate peroxidase-related (APX-R) proteins, present in all green photosynthetic eukaryotes, remains unclear. This study focuses on APX-R from Chlamydomonas reinhardtii, namely, ascorbate peroxidase 2 (APX2). We showed that apx2 mutants exhibited a faster oxidation of the photosystem I primary electron donor, P700, upon sudden light increase and a slower re-reduction rate compared to the wild type, pointing to a limitation of plastocyanin. Spectroscopic, proteomic and immunoblot analyses confirmed that the phenotype was a result of lower levels of plastocyanin in the apx2 mutants. The redox state of P700 did not differ between wild type and apx2 mutants when the loss of function in plastocyanin was nutritionally complemented by growing apx2 mutants under copper deficiencyPlant & cell physiologyAPX2 Is an Ascorbate Peroxidase-Related Protein that Regulates the Levels of Plastocyanin in Chlamydomonas.PMC1109475233663953project no.30829584grantPyr Dit Ruys SMessens JCardol PVertommen DVega de Luna FCaccamo AMisztak AERemacle CfalseAPX2 Is an Ascorbate Peroxidase-Related Protein that Regulates the Levels of Plastocyanin in Chlamydomonas.The function of ascorbate peroxidase-related (APX-R) proteins, present in all green photosynthetic eukaryotes, remains unclear. This study focuses on APX-R from Chlamydomonas reinhardtii, namely, ascorbate peroxidase 2 (APX2). We showed that apx2 mutants exhibited a faster oxidation of the photosystem I primary electron donor, P700, upon sudden light increase and a slower re-reduction rate compared to the wild type, pointing to a limitation of plastocyanin. Spectroscopic, proteomic and immunoblot analyses confirmed that the phenotype was a result of lower levels of plastocyanin in the apx2 mutants. The redox state of P700 did not differ between wild type and apx2 mutants when the loss of function in plastocyanin was nutritionally complemented by growing apx2 mutants under copper deficiency2024-01-01T00:00:00Z2024 May2026-04-16T03:16:52.752Z2026-04-16T03:10:51.598ZS-EPMC110947523859134610.1093/pcp/pcae019