Functional characterization and expression of molluscan detoxification enzymes and transporters involved in dietary allelochemical resistance
Whalen, Kristen E.
MetadataShow full item record
Understanding how organisms deal with potentially toxic or fitness-reducing allelochemicals is important for understanding patterns of predation and herbivory in the marine environment. The ability of marine consumers to tolerate dietary toxins may involve biochemical resistance mechanisms, which increase the hydrophilicity of compounds and facilitate their active efflux out of sensitive cells and tissues. While several allelochemical-responsive detoxification enzymes have been sequenced and functionally characterized in terrestrial invertebrates feeding on chemically defended host plants, there is virtually no information concerning the role of these biotransformation enzymes that may mediate feeding tolerance in marine invertebrates. The objective of this research was to assess the diversity and dietary regulation of cytochrome P450s (CYP), glutathione S-transferases (GST) and ABC transporters in the generalist marine gastropod Cyphoma gibbosum feeding on a variety of chemically defended gorgonian corals, and to identify those dietary natural products that act as substrates for these proteins. Molecular and proteomic techniques identified both allelochemically-responsive CYPs, and constitutively expressed GSTs and transporters in Cyphoma digestive glands. Inhibition of Cyphoma GST activity by gorgonian extracts and selected allelochemicals (i.e., prostaglandins) indicated that gorgonian diets are likely to contain substrates for molluscan detoxification enzymes. In vitro metabolism studies with recombinant CYPs suggested those Cyphoma enzymes most closely related to vertebrate fatty acid hydroxylating enzymes may contribute to the detoxification of ichthyodeterrent cyclopentenone prostaglandins found in abundance in selected gorgonian species. Finally, the presence and activity of multixenobiotic resistance transporters in Cyphoma and the co-occuring specialist nudibranch, Tritonia hamnerorum, suggests these efflux transporters could function as a first line of defense against dietary intoxication. Together, these results suggest marine consumers that regularly exploit allelochemical-rich prey have evolved both general (GST and ABC transporters) and allelochemical-specific (CYP) detoxification mechanisms to tolerate prey chemical defenses.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2008
Showing items related by title, author, creator and subject.
McDermott, Jill M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2015-02)This thesis examines the controls on organic, inorganic, and volatile species distributions in hydrothermal fluids venting at Von Damm and Piccard, two vent fields at the ultraslow spreading Mid-Cayman Rise, Earth’s deepest ...
Drenkard, Elizabeth J. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2015-02)Global climate models project a 21st century strengthening of the Pacific Equatorial Undercurrent (EUC). The consequent increase in topographic upwelling of cool waters onto equatorial coral reef islands would mitigate ...
Experimental and seismological constraints on the rheology, evolution, and alteration of the lithosphere at oceanic spreading centers deMartin, Brian J. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2007-02)Oceanic spreading centers are sites of magmatic, tectonic, and hydrothermal processes. In this thesis I present experimental and seismological constraints on the evolution of these complex regions of focused crustal ...