Deciphering Molecular Mechanisms Involved in Plant Volatile Emission

植物产生各种各样的挥发性化合物，促进与环境的相互作用，从吸引传粉者和种子传播者到保护自己免受病原体，寄生虫和食草动物的侵害。最近的发现使人们了解了植物如何产生挥发性化合物，但对植物细胞如何将挥发物释放到大气中却知之甚少。直到最近，人们一直认为挥发物只是扩散出细胞。然而，简单的扩散不能足够快地发生，以防止植物细胞中有毒水平的挥发物的积累。 因此，植物必须具有促进挥发物排放的细胞机制。该项目将首次描述植物挥发物从细胞中释放出来的分子过程。这项研究将确定代谢工程的新目标，以改变化合物的积累或其从植物中的释放，以改善农艺/园艺性状，生物燃料生产和作物营养价值。除了植物，化学通讯在微生物群落、昆虫的生活和动物之间的相互作用中也起着重要作用。挥发性化合物如何从这些生物体中释放出来也是一个类似的悬而未决的问题。从这个项目中获得的信息可能会提高其他生物体使用的挥发性释放机制的理解。由于植物挥发物对我们的环境有着重要的贡献，所获得的结果将为开发更精确的大气挥发物排放模型提供基础。最近的发现是，仅由扩散驱动的挥发性排放将导致细胞膜中挥发性物质的毒性水平，这提出了关于植物挥发性物质如何从细胞释放到大气中的新问题。本研究将采用遗传学、分子生物学、代谢谱、蛋白质和膜生物化学以及质量转运数学模型组成的综合策略，以（i）表征参与挥发物跨质膜输出的ABC转运蛋白;（ii）阐明小鼠突触囊泡蛋白2A的同源物PhSV 2的作用，作为一种新的囊泡运输蛋白参与挥发性排放和（iii）确定角质层的化学组成和结晶挥发性排放的影响。矮牵牛花将被用作一个模型系统，因为它们发出高水平的苯型/苯丙素类挥发物，有可用的基因组/转录组资源，并服从遗传操作。这项工作将揭示植物挥发性物质在细胞质和质膜上穿梭的生物学过程。拟议的研究将为本科生和研究生以及博士后研究人员提供多学科培训。该教育项目还将在普渡大学zipTripsTM的支持下，通过开发网络流媒体"电子实地考察"，向美国（特别是来自农村和贫困地区）和国外的数千名初中和高中学生介绍基于STEM的研究。目标是提高学生的热情，兴趣和对科学事业的看法。

Plants produce a wide diversity of volatile compounds that facilitate interactions with their environment, ranging from attracting pollinators and seed dispersers to protecting themselves from pathogens, parasites, and herbivores. Recent discoveries have allowed an understanding of how plants produce volatile compounds, but little is known about how volatiles are released from plant cells into the atmosphere. Until recently, it had been assumed that volatiles simply diffuse out of cells. However, simple diffusion cannot occur rapidly enough to prevent accumulation of toxic levels of volatiles in plant cells. Thus, plants must have cellular mechanisms that facilitate the emission of volatiles. This project will characterize the molecular processes involved in the emission of plant volatiles out of the cell for the first time. This research will identify new targets for metabolic engineering for altering either accumulation of compounds, or their release from plants, to improve agronomic/horticultural traits, biofuel production, and crop nutritional value. Beyond plants, chemical communication plays an important role in microbial communities, in the lives of insects and in interactions between animals. How volatile compounds are released from these organisms is a similar open question. The information obtained from this project may enhance understanding of volatile release mechanisms used by other organisms. Since plant volatiles significantly contribute to our environment, the results obtained will provide a foundation for development of more accurate atmospheric volatile emission models.It has long been accepted that volatile compounds, lipophilic low-molecular-weight molecules with high vapor pressures, simply diffuse out of cells. The recent finding that volatile emission driven solely by diffusion would lead to toxic levels of volatiles in membranes raises new questions about how plant volatiles are released from cells into the atmosphere. This research will employ an integrative strategy comprised of genetics, molecular biology, metabolic profiling, protein and membrane biochemistry, and mathematical modeling of mass transport to (i) characterize ABC transporters participating in export of volatiles across the plasma membrane; (ii) elucidate the role of PhSV2, a homolog of mouse synaptic vesicle protein 2A, as a novel vesicle trafficking protein involved in volatile emission and (iii) determine the effect of cuticle chemical composition and crystallinity on volatile emission. Petunia flowers will be used as a model system since they emit high levels of benzenoid/phenylpropanoid volatiles, have available genomic/transcriptomic resources, and are amenable to genetic manipulations. This work will uncover the biological processes involved in shuttling plant volatiles across the cytosol and plasma membrane. The proposed research will provide multidisciplinary training to undergraduate and graduate students, and postdoctoral researchers. The educational program will also introduce thousands of middle and high school students throughout the U.S. (particularly from rural and underprivileged areas) and abroad to STEM-based research by developing a web-streamed "electronic field trip", with support from Purdue zipTripsTM. The goals are to improve student enthusiasm, interest, and perceptions about scientific careers.