Inhibition of glycolate and D-lactate metabolism in a
            <i>Chlamydomonas reinhardtii</i>
            mutant deficient in mitochondrial respiration

Husic, Diane W.; Tolbert, N. E.

doi:10.1073/pnas.84.6.1555

Cited by 22 publications

(5 citation statements)

References 33 publications

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“…Unlike plants, C. reinhardtii has been shown both to produce ( Husic and Tolbert 1985 ) and oxidize d -lactate ( Husic and Tolbert 1987 ). To identify potential d -LDHs in C. reinhardtii , the genome sequence was searched with sequences of well-characterized NAD + -dependent d -LDH enzymes ( d -nLDH; EC 1.1.1.28) from other species.…”

Section: Resultsmentioning

confidence: 99%

Identification of the Elusive Pyruvate Reductase ofChlamydomonas reinhardtiiChloroplasts

et al. 2015

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Under anoxic conditions the green alga Chlamydomonas reinhardtii activates various fermentation pathways leading to the creation of formate, acetate, ethanol and small amounts of other metabolites including d-lactate and hydrogen. Progress has been made in identifying the enzymes involved in these pathways and their subcellular locations; however, the identity of the enzyme involved in reducing pyruvate to d-lactate has remained unclear. Based on sequence comparisons, enzyme activity measurements, X-ray crystallography, biochemical fractionation and analysis of knock-down mutants, we conclude that pyruvate reduction in the chloroplast is catalyzed by a tetrameric NAD+-dependent d-lactate dehydrogenase encoded by Cre07.g324550. Its expression during aerobic growth supports a possible function as a ‘lactate valve’ for the export of lactate to the mitochondrion for oxidation by cytochrome-dependent d-lactate dehydrogenases and by glycolate dehydrogenase. We also present a revised spatial model of fermentation based on our immunochemical detection of the likely pyruvate decarboxylase, PDC3, in the cytoplasm.

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Section: Resultsmentioning

confidence: 99%

Identification of the Elusive Pyruvate Reductase ofChlamydomonas reinhardtiiChloroplasts

et al. 2015

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“…On the other hand, none of the chlorophycean algae investigated possesses leaf peroxisomes (Stabenau 1972b, 1984, 1992a, b, 1994, Stabenau et al 1989). Their glycolate oxidizing enzyme is a dehydrogenase (Frederick et al 1973, Stabenau 1974a, b, Beezley et al 1976, Stabenau et al 1993) transferring electrons to a redox system of the mitochondrial respiratory chain (Paul and Volcani 1976, Husic and Tolbert 1987). All enzymes of the glycolate metabolism tested in the Chlorophyta are located in mitochondria (Stabenau 1972b, 1974a, b, 1984, 1994, Stabenau et al 1984a, 1989, 1993), although oxidation of glycolate was found to be also possible to some extent in chloroplasts of two algae (Goyal and Tolbert 1996, Goyal 2002).…”

Section: Introductionmentioning

confidence: 99%

Glycolate metabolism in green algae

Stabenau

Winkler

2005

Physiologia Plantarum

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Using 14C‐labelled substrates, the succession of the single steps in the glycolate metabolism was investigated in Mougeotia scalaris and Eremosphaera viridis, which, within the group of green algae, are representatives of the evolutionary lines of Charophyta and Chlorophyta, respectively. In both algae the same metabolites are formed as in higher plants, although in Eremosphaera, which in contrast to Mougeotia does not possess leaf peroxisomes, all reactions are exclusively mitochondrial. Concomitant with the oxidation of glycolate, the synthesis of ATP was demonstrated in Eremosphaera. Formation of tartronic semi‐aldehyde or other products different from those in land plants could not be demonstrated in either of these algae. Excretion of glycolate by Mougeotia and Eremosphaera is enhanced by decreasing the CO2 concentration as well as by increasing the light intensity, but is completely stopped about 14 h later. Whereas increasing enzyme activities of the glycolate pathway apparently reduces glycolate excretion in Mougeotia, activation of CO2 pumps seems to be the dominant reaction to prevent glycolate excretion in Eremosphaera. Mesostigma viride is one of the phylogenetically oldest algae in the group of Charophyceae. As this alga has already been demonstrated to contain microbodies with enzymes of leaf peroxisomes, the peroxisomal glycolate pathway must have originated at a very early stage. Surprisingly, the organelles from Mesostigma contain also the glyoxysomal marker enzyme isocitrate lyase suggesting these microbodies to be prototypes from which both glyoxysomes and leaf peroxisomes evolved.

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“…An inability to keep the stroma more oxidized would tend to enhance the production of reactive oxygen species in the chloroplast, as suggested from the measurement of lipid hydroperoxides (Table I). In addition, perturbations to mitorespiration in stm6 might also inhibit photorespiration (61), which again could cause sensitivity to photoinhibition. The reduced levels of ATP in stm6 would also impair the normal ATP-dependent repair processes leading to the observed sensitivity of growth to high light.…”

Section: Moc1 Is Required For Appropriate Expression Of Mitochondrialmentioning

confidence: 99%

The Nucleus-encoded Protein MOC1 Is Essential for Mitochondrial Light Acclimation in Chlamydomonas reinhardtii

Schönfeld

Wobbe

Borgstädt

et al. 2004

Journal of Biological Chemistry

106

107

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Mitochondrial respiration plays an important role in optimizing photosynthetic efficiency in plants. As yet, the mechanisms by which plant mitochondria sense and respond to changes in the environment are unclear, particularly when exposed to light. Here we describe the characterization of the Chlamydomonas reinhardtii mutant stm6, which was identified on the basis of impaired state transitions, a mechanism that regulates light harvesting in the chloroplast. The gene disrupted in stm6, termed Moc1, encodes a homologue of the human mitochondrial transcription termination factor (mTERF). MOC1 is targeted to the mitochondrion, and its expression is up-regulated in response to light. Loss of MOC1 causes a high light-sensitive phenotype and disrupts the transcription and expression profiles of the mitochondrial respiratory complexes causing, as compared with wild type, light-mediated changes in the expression levels of nuclear and mitochondrial encoded cytochrome c oxidase subunits and ubiquinone-NAD subunits. The absence of MOC1 leads to a reduction in the levels of cytochrome c oxidase and of rotenone-insensitive external NADPH dehydrogenase activities of the mitochondrial respiratory electron transfer chain. Overall, we have identified a novel mitochondrial factor that regulates the composition of the mitochondrial respiratory chain in the light so that it can act as an effective sink for reductant produced by the chloroplast.

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Inhibition of glycolate and D-lactate metabolism in a Chlamydomonas reinhardtii mutant deficient in mitochondrial respiration

Cited by 22 publications

References 33 publications

Identification of the Elusive Pyruvate Reductase ofChlamydomonas reinhardtiiChloroplasts

Identification of the Elusive Pyruvate Reductase ofChlamydomonas reinhardtiiChloroplasts

Glycolate metabolism in green algae

The Nucleus-encoded Protein MOC1 Is Essential for Mitochondrial Light Acclimation in Chlamydomonas reinhardtii

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