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Titolo:
Membrane lipid composition and restoration of photosynthesis during low temperature acclimation in Synechococcus sp. strain PCC 7942
Autore:
Porankiewicz, J; Selstam, E; Campbell, D; Oquist, G;
Indirizzi:
Umea Univ, Dept Plant Physiol, S-90187 Umea, Sweden Umea Univ Umea Sweden S-90187 , Dept Plant Physiol, S-90187 Umea, Sweden Mt Allison Univ, Dept Biol, Sackville, NB E4L 1G7, Canada Mt Allison UnivSackville NB Canada E4L 1G7 Sackville, NB E4L 1G7, Canada
Titolo Testata:
PHYSIOLOGIA PLANTARUM
fascicolo: 3, volume: 104, anno: 1998,
pagine: 405 - 412
SICI:
0031-9317(199811)104:3<405:MLCARO>2.0.ZU;2-J
Fonte:
ISI
Lingua:
ENG
Soggetto:
PHOTOSYSTEM-II; CYANOBACTERIUM SYNECHOCOCCUS; ANACYSTIS-NIDULANS; ACHOLEPLASMA-LAIDLAWII; FATTY-ACIDS; SYNECHOCYSTIS PCC6803; LIGHT; PHOTOINHIBITION; EXPRESSION; DESATURASE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Life Sciences
Citazioni:
38
Recensione:
Indirizzi per estratti:
Indirizzo: Porankiewicz, J Umea Univ, Dept Plant Physiol, S-90187 Umea, Sweden Umea Univ Umea Sweden S-90187 siol, S-90187 Umea, Sweden
Citazione:
J. Porankiewicz et al., "Membrane lipid composition and restoration of photosynthesis during low temperature acclimation in Synechococcus sp. strain PCC 7942", PHYSL PLANT, 104(3), 1998, pp. 405-412

Abstract

We compared temperature acclimation of the cyanobacterium Synechococcus sp. strain PCC 7942 and two psbA inactivation mutants, R2K1 and R2S2C3, following shifts from 37 to 25 degrees C. Wild-type cultures incubated in the dark at 25 degrees C showed no chill-induction of lipid desaturation, probably because the lipid acclimation is dependent on photosynthesis. Incubation in the light at 25 degrees C, however, induced considerable increases in membrane lipid desaturation, and within 24 h the monoenoic fatty acids increased from about 46 to about 57%. In parallel with this desaturation the ratio of monogalactosyldiacylglycerol to digalactosyldiacylglycerol (MGDG/DGDG)increased. Both of these lipid changes increase the repulsive forces of the hydrophobic chains of the membrane lipids and thereby alter the physical properties of the membrane. As expected, under irradiation this temperatureshift also induced a reversible replacement of the constitutive photosystem II protein, D1:1, with an alternative stress form, D1:2. Photosynthesis decreased to 42% of the control level within the initial 2 h of cold incubation. but later recovered. The D1:2 protein accumulated to high levels between 2 and 4 h after the temperature shift, when desaturation of membrane lipids and MGDG/DGDG ratio had not yet increased significantly. Much of this accumulated D1:2 protein was in a higher molecular mass form, termed D1:2*, which is probably an unprocessed precursor form of the protein. In contrastto the wild-type cells the psbA inactivation mutants, R2K1 and R2S2C3 did not accumulate any precursor form of D1 protein either at the optimal or low growth temperature. The R2S2C3 mutant strain expresses only the constitutive D1:1 protein and suffered severe photoinhibition following the temperature shift. Nevertheless; R2S2C3 eventually recovered some photosynthetic activity, induced lipiddesaturation and slowly resumed growth ar 25 degrees C, thus demonstratingacclimation to the lower growth temperature. The R2K1 mutant synthesizes only the D1:2 stress form of D1 protein and maintained oxygen evolution at a high level (ca 70% of a control rate) after the low temperature shift. Chill-induced lipid desaturation and increase inMGDG/DGDG ratio did proceed but, for unknown reasons the strain did nor resume growth at the lower temperature. The physical properties of the membrane lipids were not the limiting factor for growth resumption. Our results demonstrate that in the wild-type the chill-induced desaturation of membrane lipids follows after the exchange of the two forms of the D1proteins, but the D1 exchange results in accumulation of unprocessed D1:2*polypeptides until the lipid composition later acclimates. We also show that the lipid desaturation process in Synechococcus sp. strain PCC 7942 is dependent upon photosynthetic activity.

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Documento generato il 04/12/20 alle ore 18:44:30