Unveiling the contributions and regulation of picoeukaryotic phytoplankton in oceanic environments.

海洋中初级生产者的生长速度和命运是调节生物圈中碳通量的关键因素。虽然已知资源限制起主要调节作用，但控制浮游植物（2微米直径）生长和死亡的具体因素知之甚少。特别是，由于这些占主导地位的初级生产者体积小、下沉商低，它们的命运和在水柱中的运输的决定因素对于开发碳通量及其可能因气候变化而受到扰动的预测模型至关重要。浮游植物由蓝藻（原绿球藻和聚藻球菌）和小型真核生物组成。虽然picocyanobacteria已经受到了很多的关注，但是人们对picophyto真核生物的分布和动态知之甚少，特别是在海洋环境中。迄今为止所做的一些比较测量表明，拟植物真核生物的生产力可以与拟青绿细菌相媲美。因此，迫切需要了解拟植物真核生物在开放海洋环境中的作用。然而，这些知识只有放在整个浮游植物群落的背景下才有价值，因此，也必须包括picocyanobacteria的量化。总体目标是发展一种确定拟植物真核生物潜在生理控制的方法。将使用一种有针对性的方法，结合流程排序、cDNA文库和表达序列标签（EST），允许实时识别表达反应。这些知识将突出关键的生理限制和分子基础的微真核生物种群动态的信息，以及帮助未来分离开放海洋微真核生物的努力。这是这项工作的一个重要的额外好处，因为环境克隆图书馆的数据表明，这种微真核生物在培养馆藏中代表性很差。从长远来看，环境基因组学方法的发展也将提供一个高通量的机制来分析表达反应（mRNA）。在拟议的工作中，将在两个海洋盆地，即赤道大西洋和南太平洋中评估表达性反应。更广泛的影响。实验功能基因组学方法用于阐明对环境强迫因素的实时响应，适用于所有真核生物，并且对其他寻求确定原位响应的分子基础的微生物生态学家具有价值。此外，来自未培养的微真核生物的序列，结合分子系统发育的进展，导致了对真核生物进化的戏剧性的重新考虑；这里产生的序列应该有助于改进进化研究和“生命之树”。该项目将为几个教育层次的学生提供培训，包括处境危险的少数民族高中生、本科生和两名博士候选人。该项目的信息将被纳入研究生和本科生的海洋微生物生态学课程（由PI教授）。项目结果将通过两种基于互联网的格式提供，一种是为公众定制的，另一种是为科学界定制的。

The growth rates and fate of primary producers in the oceans are key factors regulating carbon flux in the biosphere. While resource limitation is known to play a major regulatory role, the specific factors controlling growth and mortality of picophytoplankton (2 microm diameter) are poorly understood. In particular, due to the small size and low sinking quotient of these dominant primary producers, determinants of their fate and transport in the water column are critical to the development of predictive models of carbon flux and its likely perturbation due to climate change. Picophytoplankton is composed of cyanobacteria, (Prochlorococcus and Synechococcus) and small eukaryotes. While the picocyanobacteria have received much attention, little is known about the distribution and dynamics of picophytoeukaryotes, particularly in oceanic settings. The few comparative measurements made to date indicate that the productivity of picophytoeukaryotes can rival that of picocyanobacteria. Hence, knowledge regarding the role of picophytoeukaryotes in open ocean environments is urgently needed. However, this knowledge is only valuable when put in the context of the total picophytoplankton community and, therefore, quantification of picocyanobacteria must be also be included. The overall goal is to develop a method for determining underlying physiological controls of picophytoeukaryotes. A targeted approach will be used, combining flow sorting, cDNA libraries and Expressed Sequence Tags (EST), allowing real-time expressional responses to be identified. This knowledge will highlight key physiological constraints and information on molecular underpinnings of picoeukaryotic population dynamics as well as aiding future efforts to isolate open-ocean picoeukaryotes. This is an important additional benefit from the work since environmental clone library data has demonstrated that such picoeukaryotes are poorly represented in culture collections. Long-term, the environmental genomic approach developed will also provide a high throughput mechanism for profiling expressional responses (mRNA) in the field. In the proposed work, expressional responses will be evaluated in two ocean basins, the equatorial Atlantic and the South Pacific. Broader Impacts. The experimental functional genomics approach taken to elucidate real-time responses to environmental forcing factors is applicable to all eukaryotes, and of value to other microbial ecologists seeking to identify molecular underpinnings of in situ responses. Moreover, sequences derived from uncultured picoeukaryotes, in combination with advances in molecular phylogeny, have led to a dramatic reconsideration of eukaryotic evolution; the sequences generated herein should aid refinement of evolutionary studies and the "Tree of Life". The project will provide training for students at several educational levels, including at-risk minority high school students, undergraduates and two Ph.D. candidates. Information from the project will be incorporated into graduate and undergraduate level courses on Marine Microbial Ecology (taught by the PI). Project results will be available via two internet based formats, one tailored to the general public and one for the scientific community.