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Respiratory mutants of Chlamydomonas

Lown, Felicity Jane; (2001) Respiratory mutants of Chlamydomonas. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

The aim of the work described in this thesis was to investigate the role the nuclear genome plays in the biogenesis of the respiratory chain complexes in C. reinhardtii. Previous work with the yeast S. cerevisae has demonstrated that its nuclear genome encodes subunits of complexes and also trans-acting factors that aid 1) in the expression of the complex subunits contained within the mitochondrial genome, 2) in the import and biosynthesis of the complex cofactors and 3) the assembly of the complexes. From a collection of ten C. reinhardtii mutants defective in respiratory function, two (M86 and M90) were selected for characterisation. Genetic crosses to a wild type strain confirmed that the respiratory defective phenotype in the mutants has arisen due to a mutation in the nuclear genome. Enzyme activity assays and comparison of growth rate to wild type in the presence and absence of carbon and light showed that the respiratory defective phenotype in the mutants is caused by lack of complex IV function. Molecular analysis of M90 revealed that the affected gene in the mutant codes for a protein of 105 amino acids, which contains a possible transmembrane spanning domain. Antibodies raised against the recombinant protein indicated that the protein is located in the mitochondria and is a component of complex IV. Analysis of mitochondrial gene expression in M86 demonstrated that the transcript of the only mitochondrial encoded subunit of complex IV in C. reinhardtii, COXI, is not present in the mutant. It was concluded that the affected gene in M90 codes for a subunit of complex IV and the affected gene in M86 codes for a trans-acting factor required for either the transcription of the COXI gene or the processing or stabilisation of the COXI transcript. This conclusion provides support for a model of respiratory chain biogenesis in C. reinhardtii similar to that of S. cerevisiae.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Respiratory mutants of Chlamydomonas
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences; Respiratory chain
URI: https://discovery.ucl.ac.uk/id/eprint/10100488
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