title: Chlorophyll a phytylation is required for the stability of photosystems I and II in the cyanobacterium Synechocystis sp. PCC 6803.
abstract: In oxygenic phototrophic organisms, the phytyl 'tail' of chlorophyll a is formed from a geranylgeranyl residue by the enzyme geranylgeranyl reductase. Additionally, in oxygenic phototrophs, phytyl residues are the tail moieties of tocopherols and phylloquinone. A mutant of the cyanobacterium Synechocystis sp. PCC 6803 lacking geranylgeranyl reductase, ΔchlP, was compared to strains with specific deficiencies in either tocopherols or phylloquinone to assess the role of chlorophyll a phytylatation (versus geranylgeranylation). The tocopherol-less Δhpt strain grows indistinguishably from the wild-type under 'standard' light photoautotrophic conditions, and exhibited only a slightly enhanced rate of photosystem I degradation under strong irradiation. The phylloquinone-less ΔmenA mutant also grows photoautotrophically, albeit rather slowly and only at low light intensities. Under strong irradiation, ΔmenA retained its chlorophyll content, indicative of stable photosystems. ΔchlP may only be cultured photomixotrophically (due to the instability of both photosystems I and II). The increased accumulation of myxoxanthophyll in ΔchlP cells indicates photo-oxidative stress even under moderate illumination. Under high-light conditions, ΔchlP exhibited rapid degradation of photosystems I and II. In conclusion, the results demonstrate that chlorophyll a phytylation is important for the (photo)stability of photosystems I and II, which, in turn, is necessary for photoautotrophic growth and tolerance of high light in an oxygenic environment.
authors.affiliation: Biology Division, Genetics Department, Lomonosov Moscow State University, Moscow, 119899, Russia.|Institut für Biologie/Pflanzenphysiologie, Humboldt-Universität zu Berlin, Unter den Linden 6, D-10099, Berlin, Germany.
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Shpilyov
authors.affiliation: Biology Division, Genetics Department, Lomonosov Moscow State University, Moscow, 119899, Russia.
authors.forename: Vladislav V
authors.initials: VV
authors.lastname: Zinchenko
authors.affiliation: Institut für Biologie/Pflanzenphysiologie, Humboldt-Universität zu Berlin, Unter den Linden 6, D-10099, Berlin, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Grimm
authors.affiliation: Institut für Biologie/Pflanzenphysiologie, Humboldt-Universität zu Berlin, Unter den Linden 6, D-10099, Berlin, Germany.|Institut für Biologie III, Albert-Ludwigs-Universität Freiburg, Schänzlestraße 1, D-79104, Freiburg, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Lokstein
mesh_terms: D002734:Chlorophyll / Q000235:genetics / Q000378:metabolism*; D000077194:Chlorophyll A; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D009154:Mutation; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism*; D046939:Synechocystis / Q000378:metabolism*; D024505:Tocopherols / Q000378:metabolism
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D024505:Tocopherols; D000077194:Chlorophyll A