| 1. |
- Eriksson, Mats, et al.
(författare)
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ISOLATION, PURIFICATION, AND CHARACTERIZATION OF MITOCHONDRIA FROM CHLAMYDOMONAS-REINHARDTII
- 1995
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Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 107:2, s. 479-483
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Tidskriftsartikel (refereegranskat)abstract
- Mitochondria were isolated from autotrophically grown Chlamydomonas reinhardtii cell-wall-less mutant CW 92. The cells were broken by vortexing with glass beads, and the mitochondria were collected by differential centrifugation and purified on a Percoll gradient. The isolated mitochondria oxidized malate, pyruvate, succinate, NADH, and a-ketoglutarate. Respiratory control was obtained with malate (2.0) and pyruvate (2.2) but not with the other substrates. From experiments with KCN and salicylhydroxamic acid, it was estimated that the capacity of the cytochrome pathway was at least 100 nmol O-2 mg(-1) protein min(-1) and the capacity of the alternative oxidase was at least 50 nmol O-2 mg(-1) protein min(-1). A low sensitivity to oligomycin indicates some difference in the properties of the mitochondrial ATPase from Chlamydomonas as compared to higher plants.
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| 2. |
- Villand, P, et al.
(författare)
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Carbon dioxide and light regulation of promoters controlling the expression of mitochondrial carbonic anhydrase in Chlamydomonas reinhardtii
- 1997
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 327, s. 51-57
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Tidskriftsartikel (refereegranskat)abstract
- Nuclear genes coding for carbonic anhydrase, a major mitochondrial constituent in Chlamydomonas reinhardtii grown under limited CO2, were characterized. Two genes, ca1 and ca2, were found within 7 kb of genomic DNA, organized 'head to head' in a large inverted repeat. The DNA sequences for the two genes were very similar, even in the promoter regions and in introns, indicating that the repeat is a result of a recent duplication. To study gene regulation, elements from the upstream region of cal were fused to the arylsulphatase reporter gene. After transformation,the expression of arylsulphatase was regulated similarly to the endogenous ca1/ca2 genes, even when the promoter was trimmed down to 194 nt. Expression could not be detected when 5% CO2 was bubbled into the growth medium, but was induced within hours after transfer to air. The cal promoter was not induced in low light, but at intermediate light levels its activity was dependent on the irradiance. O-2 concentration had no effect on the promoter activity, indicating that photorespiratory metabolites are not triggering the response. The availability of cells transformed with a CO2-regulated reporter gene should facilitate further studies on the metabolic adaptations that occur in some green algae in response to the external CO2 level.
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