Probing acclimation in Prochlorococcus ecotypes through analyses of global gene expression

尽管在十多年前才被发现，但海洋原氯藻已经被证明在营养稀少的热带和亚热带开阔海域中非常丰富。它是海洋环流中生产力最高的浮游植物之一，占初级生产力的80%。因此，它是世界上相当大一部分海洋的海洋食物网的重要组成部分。原氯球菌菌株的哪些适应特征使它们在贫营养环境中如此成功，它们如何适应不断变化的环境条件，以及它们如何适应条件的波动？不幸的是，我们不了解在温度、营养或光照条件变化时，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，但人们对与适应有关的关键细胞变化知之甚少，而且在不同的浮游植物群体中是否观察到类似的变化。Arrigo博士和Grossman博士将通过监测原氯球菌菌株(高光和弱光适应生态型)在施加特定的光、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。在实验室中对驯化的检查将产生大量的机械信息，这些信息最终可以用来解释在远洋浮游植物中观察到的生长速度和光合作用的特征。研究的主要目标是确定限制不同原氯球菌菌株适应高和低辐射水平、升高温度和营养胁迫的分子和生理限制因素。为了实现这一目标，研究人员将解决与驯化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驯化反应？2)细胞如何感知环境线索并将信息传递给生物合成机器？3)浮游植物对不断变化的条件有什么特定的短期和长期反应？4)对驯化至关重要的生理活动与基因表达模式之间的关系是什么？5)基因表达模式在多大程度上反映了细胞生理的变化？原氯球菌的培养将在一个正弦日光变化的昼夜循环中暴露于不同光照水平的环差中生长期间进行监测。研究人员还将启动研究，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。该项目将产生可调整的结果，以加强学生和公众对有机体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，开发和建造环差的课堂版本，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。将与当地科学培训中心，包括查博特空间和科学中心和/或旧金山的探索馆合作，开发和部署教室旋律原型和相关课程。此外，建立和使用环达因和微阵列的详细计划和协议，以及在该赠款框架下开发的任何软件，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.