NSF Postdoctoral Fellowship in Biology FY 2017: Mites, microbes, and fungal pathogens: the ecology and evolution of an indirect defense trait

这是美国国家科学基金会生物学博士后研究奖学金，隶属于“扩大生物学中代表性不足群体的参与”项目。这位名叫阿什·泽梅尼克（Ash Zemenick）的研究员正在进行研究并接受培训，以增加生物学中代表性不足的群体的参与。他的导师是密歇根州立大学的Marjorie Weber。本研究探讨了螨虫是如何影响植物病原体的。许多植物的叶子上都有小簇的毛发（“domatia”），里面有螨虫。螨虫可以通过减少病原体（细菌和真菌）的成功而使植物受益，但其机制和变化程度尚不清楚。螨虫可以通过吃掉病原体直接减少病原体的繁殖。此外，通过影响抑制病原体的微生物的丰度，螨虫可能间接影响病原体的成功。最后，因为不是所有的植物都有软骨，螨虫和/或微生物影响病原体的方式可能因植物种类而异。他正在通过一个实验来解开这些影响，这个实验操纵了螨虫进入植物的途径，以及潜在病原体的发生。这项研究将增加对这些广泛的生态相互作用的理解，并有助于农业生态系统中可持续的病原体管理。该项目还包括两个明确的更广泛的影响，解决了一些助长生物学代表性不足的刻板印象。首先，这位研究员经历过女性和跨性别者的生活，因此在指导参与研究的本科生方面起到了榜样作用。其次，他正在开发一个教材库，通过强调研究如何应用于社会问题，以及成为一名生物学家是什么样子，使生物学和生物学家人性化。该研究员使用了一些生物学家提供的例子，这些生物学家认为自己是STEM中代表性不足的群体的成员（例如，在种族、民族、性别、收入、国籍、移民身份、认知和身体能力等方面）。该研究员正在进行操纵实验，以了解螨虫如何直接（通过消耗）和/或间接（通过改变不易入侵的微生物群落组成）影响病原体的成功。20种葡萄（Vitis）的叶子将通过四种处理进行实验处理。两个（T1和T2）会阻挡螨虫，两个（T3和T4）会有螨虫。2周后，将收获一半的叶片，以评估叶片微生物群落。真菌和细菌DNA将使用条形码ITS和16S引物扩增，得到的多路扩增子将进行Illumina测序。无螨（T1和T2）和螨（T3和T4）叶片微生物群落的差异表明，寄生螨影响了葡萄球菌叶片微生物群落结构，从而间接影响了葡萄球菌病原菌的成功。另一半的重复将留在田间，螨只允许在T2和T4上复制。所有的叶子都会染上白粉病。如果螨的存在降低了葡萄叶片的病原体侵染，那么T2-T4叶片的白粉病侵染率将低于对照（T1）叶片。如果这种病原菌感染的减少是通过直接消耗而不是间接通过改良的叶片微生物群落，那么T2和T4叶片的白粉病发病率将低于T2叶片。为了评估跨叶微生物群落进化模式和病原菌抗性，将使用多维和一维比较系统发育模型来评估微生物群落组成和结构以及病原菌抗性是否与葡萄种间domatia的存在和大小进化相关。如果骨灰石的存在和大小在整个系统发育过程中与白粉病抗性相关，那么将有证据表明：A)骨灰石的选择环境包括病原体抗性，或者B)骨灰石的进化选择导致直接病原体抗性的丧失。

This is an NSF Postdoctoral Research Fellowship in Biology, under the program Broadening Participation of Groups Under-represented in Biology. The fellow, Ash Zemenick, is conducting research and receiving training that is increasing the participation of groups underrepresented in biology. The fellow is being mentored by Marjorie Weber at the Michigan State University. This research explores how mites influence the pathogens of plants. Many plants have small tufts of hairs on the leaf ("domatia") that house mites. Mites can benefit plants by reducing the success of pathogens (bacteria and fungi), but the mechanisms and extent of variation are not well understood. Mites can directly reduce success of pathogens by eating them. Also, by influencing the abundance of microbes that inhibit pathogens, mites may indirectly influence pathogen success. Finally, because not all plants have domatia, the way in which mites and/or microbes influence pathogens may vary across plant species. The fellow is disentangling these effects using an experiment that manipulates the access of mites to plants, and the occurrence of potential pathogens. This research will increase the understanding of these widespread ecological interactions, and contribute to sustainable pathogen management in agroecosystems. This project also includes two explicit broader impacts that address some stereotypes that fuel underrepresentation in biology. First, the fellow has experienced life as a woman and transgender person, and thus serves as a role model in mentoring undergraduates involved in research. Second, the fellow is developing a repository of teaching materials to humanize biology and biologists by highlighting how research applies to societal issues and what it's like to be a biologist. The fellow is using examples provided by biologists that self-identify as members of underrepresented groups in STEM (e.g. in terms of race, ethnicity, gender, income, nationality, immigrant status, cognitive and physical ability, etc.). The fellow is conducting manipulative experiment to understand how mites influence pathogen success directly (via consumption) and/or indirectly (via an altered microbial community composition that is less invasible). Leaves from 20 species of grapes (Vitis) will be experimentally manipulated with four treatments. Two (T1 and T2) will block mites, and two (T3 and T4) will have mites. After 2 weeks, half of all leaves will be harvested to assess leaf microbial communites. Fungal and bacterial DNA will be amplified using barcoded ITS and 16S primers and the resulting multiplexed amplicons will be subject to Illumina sequencing. A difference between no-mite (T1 and T2) and mite (T3 and T4) leaf microbial communities would empirically demonstrate that domatia-inhabiting mites influence leaf microbe community structure, and could therefore indirectly influence pathogen success in Vitis. The other half of replicates will remain in the field, with mites allowed only on T2 and T4. All leaves will be challenged with powdery mildew. If mite presence lowers pathogen infection of Vitis leaves, then leaves from T2-T4 will have lower infestation of powdery mildew than control (T1) leaves. If this reduction in pathogen infection is through direct consumption rather than indirectly through a modified leaf microbe community, then T2 and T4 leaves will have lower powdery mildew infestation than T2 leaves. To evaluate patterns of microbial community evolution and pathogen resistance across leaves, multi- and unidimensional comparative phylogenetic models will be used to assess whether microbial community composition and structure, as well as pathogen resistance, are evolutionarily correlated with domatia presence and size across Vitis species. If domatia presence and size are correlated with powdery mildew resistance across the phylogeny, there will be evidence for either: A) the selective environment for domatia included pathogen resistance, or B) evolution of domatia selected for the loss of direct pathogen resistance.