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Interactions of soil microbes and pioneer plant seeds: from pathogenicity to mutualism

Principal Investigators: Dr. Kathy Winnett-Murray and Dr. Greg Murray

Forests are among the most exuberant expressions of life on our planet, both for the diversity of organisms themselves and for the complexity of interactions among them. Chief among these are interactions between plants and their pollinators, seed dispersers, and seed predators and pathogens. The roles of animals in these interactions have received much attention, but the ways in which plant reproduction is affected by microbes remains poorly explored. Microbes are generally thought to act as seed pathogens, but their interactions with seeds are likely to be both more diverse and nuanced. Microbial degradation of seed coats may actually facilitate germination long before it exposes the interior of the seed to decay, for example, and microbes may interact with one another in ways that protect seeds from the pathogenic effects of some of them. "Pioneer" plants - those that specialize on colonizing recently disturbed patches of forest - constitute a model system in which to study such interactions. Many pioneer seeds include an extended period of dormancy in the soil, but the interactions between seeds and the soil microbial community, and those among the microbial species themselves, remains virtually unknown. Our research group is exploring these interactions with a common North American pioneer plant, Phytolacca americana, the seeds of which can survive in the soil for at least 40 years. Using a series of soil exposure and germination experiments, we will quantify the consequences of microbial action for seed viability and germination rate. We will also attempt to correlate these consequences with the physical effects of microbial action on the seed coat, via both scanning electron microscopy (for surface features) and light microscopy (for thickness). Genomic analyses of the microbial communities (i.e., the "microbiome") associated with seeds will shed light on the identities of the microbes present, and whether the microbial associations with seeds that survive and those that are killed are different. We also hope to assess microbial effects on the seed coats of several tropical pioneer species, and students who participate in this research may have the option to accompany the faculty mentors to Costa Rica to participate in the field component of this project. This project is a collaboration between K. Greg Murray, Kathy Winnett-Murray, and Aaron Best, all in the Department of Biology.

Representative Publications:

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