Evolutionary Analyses of the Molecular Mechanisms Regulating Ldh-B Expression

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Many researchers have suggested that variation in enzyme expression is an important mechanism for adaptive change, yet few studies address the molecular mechanisms responsible for these changes. Closely related species of the killifish, Fundulus, provide a system to investigate these mechanisms and thus address the molecular changes responsible for the adaptive variation in the glycolytic enzyme, lactate dehydrogenase B (LDH-B) expression. Populations among these species have independently evolved in different thermal environments and show adaptive changes in the levels of LDH enzyme. One can investigate the DNA sequences that control enzyme expression among these populations and, by applying the appropriate evolutionary analyses, distinguish between random DNA sequence variations and DNA sequence variations that has evolved by natural selection. The functional variation in DNA sequences that affect enzyme expression among these closely related taxa also will be investigated. By examining both the evolutionary and functional significance of DNA sequence variations, this research seeks to clarify the molecular mechanisms that produce adaptive changes in enzyme expression. The analyses among closely related species are more likely to identify the specific molecular changes responsible for adaptive variation than studies that focus on single model organisms. Thus, these studies provide unique information and a persuasive perspective concerning DNA sequence variation that could be critical for the health or performance of humans and other animals.