The Mitochondrial Genome

Cardol, Pierre; Remacle, Claire

doi:10.1016/b978-0-12-370873-1.00020-4

Cited by 10 publications

(13 citation statements)

References 89 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Chlamydomonas wild-type strain used in this work is derived from the 137c strain (cc-1373 of the Duke University). The Chlamydomonas dum22 strain is a deletion mutant lacking the left telomere, the cob gene, and part of the nd4 gene (19). Stt7-9 is a clone allelic to stt7, which can be crossed easily, unlike the original strain (gift from J.-D. Rochaix).…”

Section: Methodsmentioning

confidence: 99%

“…We resorted to Chlamydomonas mutants defective in mitochondrial activity (dums) (19) to generate a double mutant impaired in both ST and mitochondrial respiration. To this end, we crossed the dum22 mt Ϫ mitochondrial mutant (lacking both complex I and III activities) with the stt7-9 mt ϩ nuclear mutant devoid of ST because of the absence of the Stt7 kinase.…”

Section: The Absence Of State Transitions In a Respiration-defective mentioning

confidence: 99%

See 1 more Smart Citation

Impaired respiration discloses the physiological significance of state transitions in Chlamydomonas

Cardol

Alric

Girard‐Bascou

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

119

104

View full text Add to dashboard Cite

State transitions correspond to a major regulation process for photosynthesis, whereby chlorophyll protein complexes responsible for light harvesting migrate between photosystem II and photosystem I in response to changes in the redox poise of the intersystem electron carriers. Here we disclose their physiological significance in Chlamydomonas reinhardtii using a genetic approach. Using single and double mutants defective for state transitions and/or mitochondrial respiration, we show that photosynthetic growth, and therefore biomass production, critically depends on state transitions in respiratory-defective conditions. When extra ATP cannot be provided by respiration, enhanced photosystem I turnover elicited by transition to state 2 is required for photosynthetic activity. Concomitant impairment of state transitions and respiration decreases the overall yield of photosynthesis, ultimately leading to reduced fitness. We thus provide experimental evidence that the combined energetic contributions of state transitions and respiration are required for efficient carbon assimilation in this alga.cyclic electron flow ͉ photosynthesis ͉ energetic metabolism S tate transitions (ST) are a short-term photosynthetic acclimation process that controls the reversible association of the photosystem II (PSII) antenna protein complex (LHCII) with either PSII (in state 1) or photosystem I (PSI) (in state 2) (1-3). This process relies on the reversible LHCII phosphorylation involving the membrane-bound protein kinase Stt7-STN7, which recently has been identified in Chlamydomonas reinhardtii and Arabidopsis thaliana (4, 5). Phosphorylation changes lead to the migration of a fraction of the antenna between the PSII-enriched membrane domains and the PSI-enriched membrane domains within the thylakoids in plant and algal chloroplasts (3, 6).STs first were observed in unicellular green algae and originally were described as a mechanism linking the redox poise of the intersystem electron carriers to changes in the absorption capacity of the photosystems (3). Reduction of the plastoquinone (PQ) pool upon increased PSII sensitization activates the kinase via the cytochrome b 6 f complex (7). Conversely, upon increased PSI sensitization, PQH 2 oxidation inactivates the kinase. P i -LHCII then is dephosphorylated by a phosphatase (3) whose biochemical nature and regulation remain elusive.In plants, STs are of limited amplitude, involving Ϸ20% of LHCII (8). Their occurrence probably is not essential for plant survival, as suggested by the very limited effects on growth (4, 9-11) and on fitness (12) of mutations preventing STs in Arabidopsis. One of these mutants shows a marked phenotype only under a very particular regimen of fluctuating light (4). In Chlamydomonas, STs involve a larger fraction of PSII antenna than in plants, with Ϸ80% of PSII antennae being involved in this phenomenon (13), including monomeric LHCII (14). The very large redistribution of light-harvesting complexes with STs in this alga is difficult to reconcile with a role...

show abstract

Section: Methodsmentioning

confidence: 99%

Section: The Absence Of State Transitions In a Respiration-defective mentioning

confidence: 99%

Impaired respiration discloses the physiological significance of state transitions in Chlamydomonas

Cardol

Alric

Girard‐Bascou

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

119

104

View full text Add to dashboard Cite

show abstract

“…Five npq4 stt7-9 clones were isolated (see Supplemental Figures 1 and 2 online). The dum22 strain is a mitochondrial DNA deletion mutant lacking the left telomere, cob, and part of nd4 (Cardol and Remacle, 2008). Genetically modified C. reinhardtii strains PSII-His (Cullen et al, 2007) and PSI-His (Gulis et al, 2008), carrying a 6x His-tag at the C terminus of psbH and the N terminus of psaA, respectively, were used to isolate thylakoid membranes.…”

Section: Cells and Growth Conditionsmentioning

confidence: 99%

A Dual Strategy to Cope with High Light in Chlamydomonas reinhardtii

et al. 2013

Self Cite

View full text Add to dashboard Cite

Absorption of light in excess of the capacity for photosynthetic electron transport is damaging to photosynthetic organisms. Several mechanisms exist to avoid photodamage, which are collectively referred to as nonphotochemical quenching. This term comprises at least two major processes. State transitions (qT) represent changes in the relative antenna sizes of photosystems II and I. High energy quenching (qE) is the increased thermal dissipation of light energy triggered by lumen acidification. To investigate the respective roles of qE and qT in photoprotection, a mutant (npq4 stt7-9) was generated in Chlamydomonas reinhardtii by crossing the state transition-deficient mutant (stt7-9) with a strain having a largely reduced qE capacity (npq4). The comparative phenotypic analysis of the wild type, single mutants, and double mutants reveals that both state transitions and qE are induced by high light. Moreover, the double mutant exhibits an increased photosensitivity with respect to the single mutants and the wild type. Therefore, we suggest that besides qE, state transitions also play a photoprotective role during high light acclimation of the cells, most likely by decreasing hydrogen peroxide production. These results are discussed in terms of the relative photoprotective benefit related to thermal dissipation of excess light and/ or to the physical displacement of antennas from photosystem II.

show abstract

“…Their protein products participate mostly in photosynthesis or in the expression of the chloroplast genome (Barkan and Goldschmidt-Clermont, 2000). Mitochondrial genomes have become even smaller, retaining only 8, 13, and 8 open reading frames in the yeast Saccharomyces cerevisiae, in human, and in the green unicellular alga Chlamydomonas reinhardtii, respectively (Anderson et al, 1981;de Zamaroczy and Bernardi, 1986;Foury et al, 1998;Cardol and Remacle, 2009). Consequently, respiratory or photosynthetic protein complexes, with the exception of mitochondrial complex II, result from the stoichiometric assembly of subunits encoded in either the organellar or nuclear genomes.…”

Section: Introductionmentioning

confidence: 99%

The Nucleus-Encodedtrans-Acting Factor MCA1 Plays a Critical Role in the Regulation of CytochromefSynthesis inChlamydomonasChloroplasts

et al. 2011

View full text Add to dashboard Cite

Organelle gene expression is characterized by nucleus-encoded trans-acting factors that control posttranscriptional steps in a gene-specific manner. As a typical example, in Chlamydomonas reinhardtii, expression of the chloroplast petA gene encoding cytochrome f, a major subunit of the cytochrome b 6 f complex, depends on MCA1 and TCA1, required for the accumulation and translation of the petA mRNA. Here, we show that these two proteins associate in high molecular mass complexes that also contain the petA mRNA. We demonstrate that MCA1 is degraded upon interaction with unassembled cytochrome f that transiently accumulates during the biogenesis of the cytochrome b 6 f complex. Strikingly, this interaction relies on the very same residues that form the repressor motif involved in the Control by Epistasy of cytochrome f Synthesis (CES), a negative feedback mechanism that downregulates cytochrome f synthesis when its assembly within the cytochrome b 6 f complex is compromised. Based on these new findings, we present a revised picture for the CES regulation of petA mRNA translation that involves proteolysis of the translation enhancer MCA1, triggered by its interaction with unassembled cytochrome f.

show abstract

The Mitochondrial Genome

Cited by 10 publications

References 89 publications

Impaired respiration discloses the physiological significance of state transitions in Chlamydomonas

Impaired respiration discloses the physiological significance of state transitions in Chlamydomonas

A Dual Strategy to Cope with High Light in Chlamydomonas reinhardtii

The Nucleus-Encodedtrans-Acting Factor MCA1 Plays a Critical Role in the Regulation of CytochromefSynthesis inChlamydomonasChloroplasts

Contact Info

Product

Resources

About