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Title: Molecular phylogeny of glaucocystophyte and other algae using hemB : aminolaevulinic acid dehydratase in algae is magnesium-requiring
Author: Evans, C.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2001
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The glaucocystophyte algae contain simple plasmids, in common with red and green algae and higher plants. Although these groups have been shown to be monophyletic, the phylogenetic position of the latter is uncertain. The nuclear-encoded locus hemB, which encodes aminolaevulinic acid dehydratase (ALAD), was chosen to examine the phylogeny of the algae. ALAD occurs in organisms as either of two generalised classes; in most eubacteria, animals and fungi the enzyme requires Zn2+ for full activity, in plants and green algae Mg2+ is required. A sequence motif indicates which form of the enzyme is encoded by hemB. Sequence information was also collected for the algae for another nuclear gene GapC, which encodes the cytosolic form of glyceraldehye-3-phosphate dehydrogenase, for phylogenetic analysis and subsequent comparison with the hemB trees. A biochemical survey of the algae was carried out for ALAD, which indicated that most algae contain a Mg-binding ALAD. However the assay was unsatisfactory for some taxa and it was not possible to determine which kind of ALAD they possess. These initial results were then supplemented with sequence data for hemB in a number of different algae. Full and partial sequences were obtained from glaucocystophyte, red and brown algae and where this sequence included the metal-binding site, this always indicated a Mg2+ requirement for ALAD. The position in the trees of bacteria with a Mg-binding ALAD relative to the algae, suggests that horizontal gene transfer may have been the mechanism by which plants and algae obtained a Mg-binding ALAD.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available