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Chlorophyll a phytylation is required for the stability of photosystems I and II in the cyanobacterium S ynechocystis sp. PCC 6803
Author(s) -
Shpilyov Alexey V.,
Zinchenko Vladislav V.,
Grimm Bernhard,
Lokstein Heiko
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12044
Subject(s) - photosystem , chlorophyll , photosystem i , phototroph , biochemistry , cyanobacteria , chemistry , photosynthesis , biology , botany , photosystem ii , bacteria , genetics
Summary 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 S ynechocystis sp. PCC 6803 lacking geranylgeranyl reductase, Δ chlP , 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 Δ hpt 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 Δ menA mutant also grows photoautotrophically, albeit rather slowly and only at low light intensities. Under strong irradiation, Δ menA retained its chlorophyll content, indicative of stable photosystems. Δ chlP may only be cultured photomixotrophically (due to the instability of both photosystems I and II ). The increased accumulation of myxoxanthophyll in Δ chlP cells indicates photo‐oxidative stress even under moderate illumination. Under high‐light conditions, Δ chlP 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.