Nutritional, environmental, and genetic regulation of toxicity and growth in Dinophysis
The dinoflagellate genus Dinophysis is important from ecological, evolutionary, and public health perspectives. In the former category, some members of this genus derive their nutrition through a unique, multi-stage process requiring cryptophyte and ciliate prey. Evolutionarily, the modification of cryptophyte chloroplasts during feeding and their subsequent utilization for photosynthesis provides a model system for investigations of plastid acquisition and evolution. From the public health perspective, Dinophysis species are responsible for the vast majority of diarrhetic shellfish poisoning (DSP) cases. DSP is a syndrome predominantly associated with consumption of shellfish that have accumulated Dinophysis toxins. It is a major health and economic problem for many countries and is among the most important and widespread of the harmful algal bloom (HAB)-associated poisoning syndromes.
For decades, many aspects of Dinophysis physiology, toxicity, and genetics have remained intractable due to our inability to grow and maintain these organisms in laboratory cultures. As a result of a recent breakthrough, however, this obstacle no longer exists and an array of important experiments and measurements are now possible. The opportunities for major advances on multiple fronts are significant. Here we propose a comprehensive study to investigate nutritional, environmental, and genetic regulation of toxicity and growth in Dinophysis. Our overall hypothesis is that toxin variability in Dinophysis is regulated not only by genetic differences among Dinophysis species and strains, but also by differences in ciliate and cryptophyte food availability and quality, and by environmental influences as well. We propose to establish and genetically characterize a geographically diverse culture collection that will include a variety of isolates of Dinophysis, Myrionecta and other ciliates, and cryptophytes. Much of this culture collection has already been assembled in advance of this submission. The culture assemblage will then be used to investigate Dinophysis and ciliate feeding selectivity, grazing rates, and growth. The next major objective is to explore mechanisms underlying toxin variability in Dinophysis. This will include analysis of geographically dispersed Dinophysis isolates fed with an array of ciliates and cryptophytes, as well as an examination of the role of environmental factors such as temperature, light, and nutrients in toxin production. The proposed work will rely on a proven system and methods – cultures of Dinophysis that have been growing at high rates in the PI’s laboratory many months, established experimental protocols, and sophisticated toxin chemistry using state-of–the-art instruments and techniques. We have worked for several years (without funding) to set up the infrastructure and gain the experience needed to conduct and justify the experiments proposed here, recognizing the need to convince reviewers and others that the work is indeed feasible. We can say with confidence that we have reached the point where we are no longer constrained by an inability to manipulate Dinophysis species in the laboratory. We can thus move forward and begin to answer longstanding questions in dinoflagellate physiology, ecology, toxicity, and evolution while providing valuable information on a significant public health and economic problem.
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