title: Modulation of photosynthetic activity and photoprotection in Haematococcus pluvialis cells during their conversion into haematocysts and back.
abstract: The engagement of different photoprotective mechanisms in the cells of the carotenogenic astaxanthin-accumulating chlorophyte Haematococcus pluvialis (i) under favorable conditions, (ii) in the course of stress-induced haematocyst formation and (iii) during recovery from the stress was studied. To this end, we followed the changes in primary photochemistry, electron flow at the acceptor side of photosystem II, and non-photochemical quenching (NPQ) using PAM chlorophyll fluorimetry. A general trend recorded in the stressed cells undergoing transition to haematocysts (and reversed during recovery from the stress) was a gradual reduction of the photosynthetic apparatus accompanied by down-regulation of energy-dependent photoprotective mechanisms such as NPQ, along with the accumulation of astaxanthin. On this background, a transient up-regulation of the photosynthetic activity was detected at the intermediated stages (20-50 h of the stress exposure) of haematocyst formation. This phenomenon was tentatively related with the peak of metabolic activity found earlier in the forming haematocysts. The role of secondary carotenogenesis coupled with a reversible transition from 'active' (energy-dependent) to 'passive' photoprotective mechanisms in the extremely high stress tolerance of carotenogenic phototrophs is discussed.
authors.affiliation: Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, Russia, 119234.|National Research Nuclear University MEPhi, Centre for Humanities Research and Technology, Moscow, Russia.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Chekanov
authors.affiliation: Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, Russia, 119234.
authors.forename: Alexander
authors.initials: A
authors.lastname: Lukyanov
authors.affiliation: Microalgal Biotechnology Laboratory, French Associates Institute for Agriculture and Biotechnology of Drylands, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beersheba, Israel.
authors.forename: Sammy
authors.initials: S
authors.lastname: Boussiba
authors.affiliation: Microalgal Biotechnology Laboratory, French Associates Institute for Agriculture and Biotechnology of Drylands, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beersheba, Israel.
authors.forename: Claude
authors.initials: C
authors.lastname: Aflalo
authors.affiliation: Department of Bioengineering, Faculty of Biology, Moscow State University, GSP-1, Moscow, Russia, 119234. solovchenko@mail.bio.msu.ru.|Timiryazev Institute of Plant Physiology, Russian Academy of Science, Moscow, Russia. solovchenko@mail.bio.msu.ru.
authors.forename: Alexei
authors.initials: A
authors.lastname: Solovchenko
mesh_terms: D002338:Carotenoids / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000460:Chlorophyta / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects; D015536:Down-Regulation; D005453:Fluorescence; D008027:Light; D055668:Photochemical Processes; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D013312:Stress, Physiological; D015854:Up-Regulation; D024341:Xanthophylls / Q000378:metabolism
chemical_list: D045332:Photosystem II Protein Complex; D024341:Xanthophylls; D002734:Chlorophyll; D002338:Carotenoids; C005948:astaxanthine
keywords: Carotenogenesis; Non-photochemical quenching; Photoprotection; Stress