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、寄生虫和草食动物的伤害。最近的发现让人们了解了植物是如何产生挥发性化合物的，但人们对植物细胞如何将挥发性化合物释放到大气中知之甚少。直到最近，人们一直认为挥发物只是从细胞中扩散出来。然而，简单的扩散发生得不够快，不足以防止植物细胞中有毒水平的挥发物积累。因此，植物必须有促进挥发物释放的细胞机制。这个项目将首次描述植物挥发物从细胞中释放出来所涉及的分子过程。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从植物中释放，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，化学交流在微生物群落、昆虫的生活和动物之间的相互作用中也发挥着重要作用。挥发性化合物是如何从这些生物体中释放出来的，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加强对其他生物所使用的挥发性释放机制的了解。由于植物挥发物对我们的环境有重要的贡献，所获得的结果将为开发更准确的大气挥发性排放模型提供基础。长期以来，人们一直认为，挥发性化合物是具有高蒸汽压的亲油小分子，只是简单地扩散到细胞外。最近发现，仅由扩散驱动的挥发性排放会导致膜中挥发性物质的有毒水平，这引发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物质传输的数学模型相结合的策略，以(I)表征参与挥发性物质跨质膜输出的ABC转运蛋白；(Ii)阐明小鼠突触囊泡蛋白2A的同源蛋白PhSV2作为一种新的囊泡运输蛋白参与挥发性物质释放的作用；(Iii)确定角质层化学成分和结晶度对挥发性物质释放的影响。矮牵牛花将被用作模式系统，因为它们释放出高水平的苯类/苯丙类挥发物，拥有可用的基因组/转录组资源，并且易于进行遗传操作。这项工作将揭示植物挥发物穿梭在细胞质和质膜上的生物过程。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zipTripsTM的支持下，通过开发网络流媒体的“电子实地考察”，向全美(特别是来自农村和贫困地区)和国外的数千名初中生和高中生介绍基于STEM的研究。目标是提高学生对科学职业的热情、兴趣和认知。

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.