Effect of Chlamydomonas plastid terminal oxidase 1 expressed in tobacco on photosynthetic electron transfer

• Published in: The Plant journal : for cell and molecular biology 2016, Vol.85 (2), p.219-228
• Main Authors: Feilke, Kathleen, Streb, Peter, Cornic, Gabriel, Perreau, François, Kruk, Jerzy, Krieger‐Liszkay, Anja
• Format: Article
• Language: English
• Subjects: abiotic stress; absorption; Biosynthesis; Botany; Carbon dioxide; carotenoids; Chlamydomonas - enzymology; Chlamydomonas - genetics; Chlamydomonas reinhardtii; Chlamydomonas reinhardtii PTOX1; chlorophyll; electron transfer; Electron Transport - genetics; fluorescence; high performance liquid chromatography; High pressure; Life Sciences; Liquid chromatography; Membranes; Nicotiana - enzymology; Nicotiana - genetics; Nicotiana tabacum; oxidation; Oxidative stress; Oxidoreductases - genetics; Oxidoreductases - metabolism; photoinhibition; photooxidative stress; Photosynthesis; Photosynthesis - genetics; photosynthetic electron transport; Plants, Genetically Modified - enzymology; Plants, Genetically Modified - genetics; Plants, Genetically Modified - metabolism; plastid terminal oxidase; Plastids; Plastids - enzymology; regulation; Thermoluminescence; thylakoids; Tobacco
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.13101

The plastid terminal oxidase PTOX is a plastohydroquinone:oxygen oxidoreductase that is important for carotenoid biosynthesis and plastid development. Its role in photosynthesis is controversially discussed. Under a number of abiotic stress conditions, the protein level of PTOX increases. PTOX is thought to act as a safety valve under high light protecting the photosynthetic apparatus against photodamage. However, transformants with high PTOX level were reported to suffer from photoinhibition. To analyze the effect of PTOX on the photosynthetic electron transport, tobacco expressing PTOX‐1 from Chlamydomonas reinhardtii (Cr‐PTOX1) was studied by chlorophyll fluorescence, thermoluminescence, P700 absorption kinetics and CO₂ assimilation. Cr‐PTOX1 was shown to compete very efficiently with the photosynthetic electron transport for PQH₂. High pressure liquid chromatography (HPLC) analysis confirmed that the PQ pool was highly oxidized in the transformant. Immunoblots showed that, in the wild‐type, PTOX was associated with the thylakoid membrane only at a relatively alkaline pH value while it was detached from the membrane at neutral pH. We present a model proposing that PTOX associates with the membrane and oxidizes PQH₂ only when the oxidation of PQH₂ by the cytochrome b₆f complex is limiting forward electron transport due to a high proton gradient across the thylakoid membrane.