Probing acclimation responses in Prochlorococcus ecotypes through analyses of global gene expression

尽管在十多年前才被发现，但原绿球藻（Prochlorococcus marinus）已被证明在热带和亚热带少营养开放海洋中非常丰富。它是海洋环流中产量最高的浮游植物之一，占初级产量的80%。因此，对于世界上很大一部分海洋来说，它是海洋食物网的重要组成部分。原绿球藻菌株的什么适应特征使它们在少营养环境中如此成功，它们是如何适应不断变化的环境条件的，以及它们是如何适应条件波动的？不幸的是，我们不了解在温度、营养或光照条件变化的情况下，控制驯化的动态或边界的过程。此外，虽然适应反应发生在适应的范围内，但对与适应有关的关键细胞变化知之甚少，以及是否在不同的浮游植物群中观察到类似的变化。Drs。Arrigo和Grossman将通过监测原绿球藻菌株（包括高光适应和低光适应生态型）在施加特定光、营养和温度条件后的生理和分子反应，探索适应过程和适应限制浮游植物适应的方法。在实验室中对适应性的研究将产生广泛的机制信息，这些信息最终可以用来解释在开阔海洋浮游植物中观察到的光合作用的生长速度和特征。该研究的主要目标是确定不同原绿球藻菌株适应高、低辐照水平、温度升高和营养胁迫的能力的分子和生理限制。为了实现这一目标，研究者将解决与适应的特征和机制有关的几个问题：1)不同的环境线索如何调节适应反应？2)细胞如何感知环境信号并将信息传递给生物合成机器？3)浮游植物对环境变化的短期和长期反应是什么？4)对驯化至关重要的生理活动与基因表达模式之间有什么关系？5)基因表达模式在多大程度上反映了细胞生理学的变化？原绿球藻培养物将在暴露于昼夜循环中以正弦日光变化传递的不同光照水平后，在cyclodyne中生长期间进行监测。研究人员还将开始研究，以确定培养物对不同温度和营养水平的反应，主要是在批次培养中。该项目将产生的结果可用于提高学生和公众对生物与其环境之间关系的理解。这些研究人员将与科学中心的科学教育工作者密切合作，开发和建造一个课堂版的cyclodyne，并围绕它设计一系列实验，探索水生微生物与环境之间的相互作用。原型教室cyclodynes和相关课程将与当地科学培训中心合作开发和部署，包括Chabot空间和科学中心和/或旧金山的探索博物馆。此外，建造和使用摆轮发电机和微阵列的详细计划和协议，以及在此资助下开发的任何软件，将在专门为该项目开发的网站上公布。

Despite its discovery only a little over a decade ago, the prochlorophyte, Prochlorococcus marinus, has been shown to be very abundant in oligotrophic tropical and subtropical open oceans. It is among the most productive phytoplankton in the oceanic gyres, accounting for up to 80% of primary production. As such, it is an important component of the marine food web for a significant fraction of the world's oceans. What adaptive features of Prochlorococcus strains make them so successful in oligotrophic environments, how have they adapted to changing environmental conditions and how do they acclimate as conditions fluctuate? Unfortunately we do not understand the processes that control either the dynamics or the boundaries of acclimation with respect to changing temperature, nutrient, or light conditions. Furthermore, while acclimation responses occur within the boundaries of adaptation, little is known about the critical cellular changes linked to acclimation, and if similar changes are observed among different groups of phytoplankton. Drs. Arrigo and Grossman will explore acclimation processes and the means by which adaptation has limited acclimation of phytoplankton by monitoring physiological and molecular responses of Prochlorococcus strains (both a high light- and low light-adapted ecotype) following the imposition of specific light, nutrient, and temperature conditions. Examination of acclimation in the laboratory will yield extensive mechanistic information that can eventually be used to explain growth rates and features of photosynthesis observed in open ocean phytoplankton. The primary goal of the research is to determine the molecular and physiological constraints that set limits on the ability of the different Prochlorococcus strains to acclimate to both high and low irradiance levels, increased temperatures, and nutrient stress. To attain this goal the investigators will address several questions related to features and mechanisms of acclimation: 1) How do different environmental cues modulate the acclimation responses? 2) How do cells sense environmental cues and convey that information to biosynthetic machinery? 3) What are the specific short-term and long-term responses of phytoplankton to changing conditions? 4) What are the relationships between physiological activities critical for acclimation and patterns of gene expression? 5) To what extent do the patterns of gene expression reflect changes in cell physiology? Prochlorococcus cultures will be monitored during growth in a cyclodyne following exposure to various light levels delivered over a day-night cycle with sinusoidal daylight variation. The investigators will also initiate studies to determine responses of cultures to different temperatures and nutrient levels, mostly in batch cultures. The project will generate results that can be adapted to enhance student and public understanding of relationships between organisms and their environment. These researchers will work closely with science educators at science centers to develop and build a classroom version of the cyclodyne, and design a series of experiments around it that explore the interaction between aquatic microbes and the environment. Prototype classroom cyclodynes and an associated curriculum will be developed and deployed in collaboration with local science training centers, including the Chabot Space and Science Center and/or the Exploratorium in San Francisco. Furthermore, detailed plans and protocols for building and using the cyclodyne and the microarrays, plus any software developed under the umbrella of this grant, will be made public on a website developed specifically for this project.