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Title: The evolution of beetle bioluminescence
Author: Day, John C.
ISNI:       0000 0004 2681 7334
Awarding Body: Oxford Brookes University
Current Institution: Oxford Brookes University
Date of Award: 2009
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The research presented in this thesis examines the evolution of bioluminescence in beetles. The study utilises two enzymes implicated in the bioluminescent reaction of fireflies and glow-worms; the protein luciferase and the luciferin regenerating enzyme (LRE). A range of parallagous genes for both enzymes were identified in bioluminescent and non-bioluminescent taxa using degenerate primer PCR. Combined with genomic and database sequences phylogenies were reconstructed using Bayesian and Maximum Likelihood approaches. The LRE share identity with a large family of enzymes including the senescence marker 30 (SMP30), gluconolanctonases and LRE (SGL) which included enzymes involved in ascorbic acid biosynthesis. Orthologous primary sequence comparisons revealed key conserved residues that formed a putative active site when mapped onto the tertiary structure of the bacterial SGL orthologue. As a result a putative active site was predicted for the LRE and key residues identified that may be involved in luciferin binding. The phylogeny revealed two main coleopteran SGL clades with species-specific paralogues present in both clades, which suggests early duplication in the Coleoptera and potential functional divergence of SGL enzymes. The highest degree of divergence was found between a subclade of group I (la) containing all the lampyrid LREs and group II suggesting functional divergence between these two classes of enzymes in the Lampyridae. Phylogenetic reconstruction of luciferase and luciferase like paralogues in the Lampyridae identified one principle luciferase clade containing multiple novel genes from single species and three luciferase-like clades. In T. castaneum six ESTassociated sequences were identified none of which were present in the luciferase clade. Multiple luciferase genes were identified from members of the Photurinae and the Luciolinae. The majority of luciferase residues were identified to be under purifying selection as opposed to positive selection. No luciferase paralogues were found in Cantharis species suggesting a loss of this gene paralogue in nonbioluminescent members of the Cantharoidea. Finally, the potential for paralogues to be present in a genomic tandem array was investigated by genome walking upstream of the luciferase gene in the glow-worm Lampyris noctiluca. Although no luciferase paralogues were identified in 7 kb of upstream region the remnants of a retrotransposase was determined. The evolutionary implications of these findings are discussed in light of recent published research.
Supervisor: Bailey, Mark ; Possee, Robert Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral