title: Alteration of chromium effect on photosystem II activity in Chlamydomonas reinhardtii cultures under different synchronized state of the cell cycle.
abstract: The inhibitory effect of chromium (Cr) on photosystem II (PSII) activity was investigated in the green alga Chlamydomonas reinhardtii during different phases of the cell cycle. Algae were cultivated in continuous light or a light/dark cycle (16:8 h) to obtain a synchronously dividing cell culture. The cell division phases were determined with the DNA-specific fluorescent probe SYBR green using flow cytometry. The effect of Cr on PSII activity was investigated after a 24-h treatment with algal cultures having different proportions of newly divided cells (G(0)/G(1)), dividing cells at the DNA replication phase (S), and dividing cells at the mitosis phase (G(2)/M). Using chlorophyll a fluorescence parameters based on PSII electron transport capacity in dark- (Φ(M)II) and light-adapted (Φ'(M)II) equilibrium state, we found that the effect of Cr differs depending on the stage of the cell cycle. When algal cultures had a high proportion of cells actively dividing (M phase), the toxic effect of Cr on PSII activity appeared to be much higher and PSII quantum yield was decreased by 80 % compared to algal cultures mainly in the G(0)/G(1) phase. Therefore, the inhibitory effect of Cr on photosynthesis appears to be different according to the cell cycle state of the algal population.
authors.affiliation: Department of Chemistry, University of Quebec in Montreal, C.P. 8888, Succ. Centre-Ville, Montreal, Quebec, H3C 3P8, Canada.
authors.forename: Olivier
authors.initials: O
authors.lastname: Didur
authors.forename: David
authors.initials: D
authors.lastname: Dewez
authors.forename: Radovan
authors.initials: R
authors.lastname: Popovic
mesh_terms: D018929:Cell Culture Techniques; D002453:Cell Cycle / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D016825:Chlamydomonas reinhardtii / Q000187:drug effects* / Q000378:metabolism; D002857:Chromium / Q000494:pharmacology*; D004261:DNA Replication / Q000187:drug effects; D005434:Flow Cytometry; D008938:Mitosis / Q000187:drug effects; D045332:Photosystem II Protein Complex / Q000187:drug effects* / Q000378:metabolism
chemical_list: D045332:Photosystem II Protein Complex; D002857:Chromium