Went 2021 Batchelor thesis

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Went N (2021) Oxygen dependence of photosynthesis and light-enhanced dark respiration studied by High-Resolution PhotoRespirometry. Batchelor thesis:26 pp.

» Went 2021 Batchelor thesis

Went N (2021) Batchelor thesis

Abstract: The bioenergetic crosstalk between mitochondria and chloroplasts plays a key role in maintaining metabolic integrity and controlling metabolite production for growth and regulation of cell concentration. Dark respiration and photosynthesis were studied in the green alga Chlamydomonas reinhardtii at varying oxygen concentrations and three cell concentrations. Light-enhanced dark respiration LEDR was measured after light-dark transitions (Shimakawa et al 2020). Algae were grown photoautotrophically at 25 °C and a light intensity of 100 µmol∙s-1∙m-2. High-resolution respirometry based on the Oroboros O2k is extensively applied to the study of mitochondrial physiology in the biomedical field (Doerrier et al 2018; Gnaiger 2020). Real-time net O2 production rate (net photosynthesis NP) was measured with the NextGen-O2k. Light intensities (blue) were controlled with the O2k-PhotoBiology-Module in the range from 0 to 350 µmol∙s-1∙m-2. Dark respiration DR ̶ determined initially at normoxia ̶ was independent of cell concentration when expressed as O2 flow per cell. At stepwise increments of light intensity NP was stimulated to a maximum while O2 concentration increased from 220 µM to 350 up to 650 µM depending on cell count per volume in the closed reaction chamber. Alternatively, O2 concentration was prevented from reaching severe hyperoxia by intermittent downregulation of O2 concentration in the chamber. Independent of cell concentration, NP was inhibited gradually from normoxia to severe hyperoxia by up to 40 %. LEDR was a sharp (negative) maximum of respiration at approximately 30-60 s after light-dark transitions, increasing 3- to 4-fold compared to DR. No O2 dependence could be assigned to LEDR measured at normoxia and hyperoxia. Taken together, the present results indicate that the decline of net O2 production under hyperoxia was not caused by compensatory light-enhanced photorespiration LEPR, if LEDR is proportional to LEPR (Shimakawa et al. 2020), but was due to inhibition of photosynthesis at high O2 concentrations.

Supplement: Went N, Di Marcello M, Gnaiger E (2021) Oxygen dependence of photosynthesis and light-enhanced dark respiration studied by High-Resolution PhotoRespirometry. https://doi.org/10.26124/mitofit:2021-0005

Bioblast editor: Gnaiger E


» O2k-Publications: Chlamydomonas

Labels: MiParea: Respiration 

Organism: Plants 

Regulation: Oxygen kinetics  Coupling state: ROUTINE 

HRR: Oxygraph-2k, NextGen-O2k