SGER: Diazotrophic Yeast of Poplar Trees

这是探索性研究(SGER)的一小笔赠款，目的是验证微生物生理学方面的一项戏剧性发现，这项发现对生态学、进化生物学和农业具有重要意义。生活在植物体内的微生物被称为内生菌，它们可以通过各种方式显著促进植物的生长。尽管内生菌为植物的生长提供了必要的因素，但对许多重要农作物内生菌的多样性和功能的深入研究还有待于进行。杨树是一种快速生长的树木，用于生产纸张和木材。它还可以用于生产能源和修复污染物。这种经济上重要的物种的内生群落包括各种微生物，其中许多是重氮营养的(固氮)。在研究杨树内的固氮内生菌时，几条初步证据表明，其中一些菌株是酵母菌。这是一个危险的发现，需要用严格的实验来验证，因为到目前为止，重氮营养只在原核微生物(细菌和古菌)中发生。因此，这项提议的目的是明确测试杨树上的酵母分离物是否不含原核生物污染物，以及是否确实固定了大气中的氮。这些测试将涉及生长和生化分析，以及基因克隆、测序和编码与固氮有关的酶的基因的表达。如果结果是肯定的，这将意味着我们目前对固氮的理解发生了范式转变，因为这将是第一个固氮真核生物的例子。这项研究可能会对农业和环境科学产生重大影响。将豆科植物/根瘤菌共生固氮能力推广到非豆科作物，以减少对化肥的依赖，一直是人们追求的目标。对酵母菌株的研究显然可以将大气中的氮转化为可用于非豆科作物的形式，这不仅可能导致将其应用于其他非豆类作物，还可能导致将这种能力转移到作物本身的方法。它还将对理解地球上生命的进化以及迫使重新考虑生态系统中的氮循环模型产生深远的影响。其他更广泛的影响将包括培训本科生和研究生的机会，以及对科学领域女性的支持。对高中生和美国杨树种植者的推广也将纳入该项目。

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.