Ecological Aspects of Plant Selenium Hyperaccumulation: Below and Beyond

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IOS-0817748 PI: Elizabeth Pilon-SmitsEcological aspects of plant selenium hyperaccumulation - below and beyondThe element selenium (Se) is essential for many organisms. Dietary Se can boost the immune system and prevent cancer and bacterial and viral infections including HIV. On the other hand, Se is toxic at higher levels and Se is a serious environmental pollutant worldwide. Some plants native to the Western U.S., commonly called ?locoweeds?, hyperaccumulate Se up to 1 percent of their dry weight. The investigators propose that these plants hyperaccumulate Se as a defense compound against herbivory and microbial infection, and are interested in the effects of the accumulated Se on the ecological interactions of hyperaccumulators. Over the past three years they have discovered that Se accumulation protects plants from a variety of herbivores, due to both deterrence and toxicity. At the same time, several Se-tolerant specialist herbivores were found to feed on hyperaccumulators, and to accumulate fairly high Se levels. Continued studies will investigate how the Se in hyperaccumulators affects ecological interactions in their local ecosystem, going "below and beyond" what has been discovered so far. More specifically, effects of accumulated root Se on root-zone interactions of hyperaccumulator plants with neighboring plants, root-associated invertebrates, and root-associated microbes will be examined. Beyond the direct plant-herbivore or plant-microbe interactions, the researchers will investigate the effects of Se accumulation by specialist herbivores or microbes on the ecological interactions of these specialists that may further mobilize Se into the food chain. The findings from this project should have broad implications, and applications in medicine and agriculture. The effects of hyperaccumulation of Se on herbivores and other ecological partners are probably similar for other toxic metals and metalloids. Understanding the movements of hyperaccumulated elements in the food chain will be critical to the practices of phytoremediation (environmental cleanup using plants) and of cultivating element-fortified foods with health-benefiting properties. In addition, knowledge of how plant Se accumulation affects growth and survival of pathogens or herbivores, and identification of specialist Se-tolerant pathogens or herbivores may be used to both control plant pests and Se-hyperaccumulating noxious weeds.