SGER: Diazotrophic Yeast of Poplar Trees

University Of Washington, Seattle WA

Investigators

Abstract

This is a Small Grant for Exploratory Research (SGER) to validate what could be a dramatic discovery in microbial physiology with important implications for ecology, evolutionary biology and agriculture. Microorganisms that live within plants are called endophytes, and they can dramatically enhance plant growth in various ways. Although endophytes provide essential factors for plant growth, in-depth studies into the diversity and function of endophytes of many important crop plants have yet to be performed. Poplar is a fast-growing tree that is used for the production of paper and lumber. It can also be used in the production of energy, and in the remediation of pollutants. The endophytic community of this economically-important species includes a diverse range of microorganisms, many of which are diazotrophic (nitrogen-fixing). While studying the nitrogen-fixing endophytes within poplar trees, several lines of preliminary evidence have indicated that some of the isolates were yeasts. This is a risky finding that needs to be validated with rigorous experiments because to date, diazotrophy is only known to occur in prokaryotic microogranisms (bacteria and archaea). Accordingly, this proposal aims to test unequivocally, whether the yeast isolates from poplar are free of prokaryotic contaminants and are, in fact, fixing atmospheric nitrogen. These tests will involve growth and biochemical assays, as well as gene cloning, sequencing and expression of genes that code for enzymes involved in nitrogen fixation. If the results are positive, it will mean a paradigm shift in our current understanding of nitrogen fixation since it would be the first example of a nitrogen-fixing eukaryote. This research could have a major impact on agricultural and environmental science. It has long been a goal to extend the nitrogen-fixing ability of the legume/Rhizobium symbiosis to non-legume crops in order to reduce our dependence on chemical fertilizers. The study of yeast strains that can apparently transform atmospheric nitrogen into usable forms for a non-legume crop could lead not only to its application on other non-legumes but also to methods of transferring this ability to crop plants themselves. It will also have profound implications in understanding the evolution of life on earth, as well as forcing a reconsideration of models of nitrogen cycling in ecosystems. Other broader impacts will include opportunities for training undergraduate and graduate students, as well as support for women in science. Outreach to high school students and U.S. poplar growers will also be integrated in to the project.