Iron and Light Limitation in Ecologically Important Polar Diatoms: Comparative Transcriptomics and Development of Molecular Indicators

围绕南极洲的南大洋正在迅速变化，以应对地球变暖的气候。这些变化无疑将影响初级生产者群体（处于食物链基础的生物，特别是利用阳光作为能量的植物类生物），因为它们改变了影响其生长和组成的条件。由于浮游植物等初级生产者在全球生物地球化学循环中发挥着重要作用，因此必须了解它们将如何应对环境变化。南大洋某些地区浮游植物的生长受到化学和物理性质的急剧变化的限制，这些变化在空间和时间上都有差异。光和铁已被确定为影响南极沃茨内浮游植物丰度和分布的关键变量。被称为硅藻的微型藻类是浮游植物和海冰群落的主要成员，占初级生产的很大比例。该项目的总体目标是确定极性硅藻对不同光和铁条件的生理反应的分子基础。该项目应提供一种手段，以评价这些因素在多大程度上调节南极沃茨的硅藻生长和影响净群落生产力。 该项目还将进一步推动NSF的目标，即向公众提供科学发现和培训新一代科学家。它将通过将研究目标转化为中学生易于获取的教育材料，促进与极地有关的主题的教学。 该项目还将提供资金，使一名研究生和几名本科生能够接受现代生物学技术和观点的培训。尽管许多研究已经调查了极地硅藻如何受到不同的光和铁的影响，但导致其独特生理反应的细胞机制仍然未知。使用比较转录组学，在几个生态重要的极地硅藻最近从南极沃茨分离和不同的铁和光照条件下生长的关键基因和代谢途径的表达模式将进行检查。 此外，将通过鉴定铁和光反应基因，在这些极地硅藻中开发铁和光限制的分子指标，这些基因的表达模式可用于确定其生理状态。在实验室培养验证后，这些指标将通过元转录组测序的方式来检查铁和光的限制在自然硅藻组合收集沿着环境梯度在南极半岛西部沃茨。为了充分了解浮游植物在南大洋生物地球化学循环中的作用，必须采用可靠的方法，说明浮游植物在任何特定时间和地点的生理状况。

The Southern Ocean surrounding Antarctica is changing rapidly in response to Earth's warming climate. These changes will undoubtedly influence communities of primary producers (the organisms at the base of the food chain, particularly plant-like organisms using sunlight for energy) by altering conditions that influence their growth and composition. Because primary producers such as phytoplankton play an important role in global biogeochemical cycling, it is essential to understand how they will respond to changes in their environment. The growth of phytoplankton in certain regions of the Southern Ocean is constrained by steep gradients in chemical and physical properties that vary in both space and time. Light and iron have been identified as key variables influencing phytoplankton abundance and distribution within Antarctic waters. Microscopic algae known as diatoms are dominant members of the phytoplankton and sea ice communities, accounting for significant proportions of primary production. The overall objective of this project is to identify the molecular bases for the physiological responses of polar diatoms to varying light and iron conditions. The project should provide a means of evaluating the extent these factors regulate diatom growth and influence net community productivity in Antarctic waters. The project will also further the NSF goals of making scientific discoveries available to the general public and of training new generations of scientists. It will facilitate the teaching and learning of polar-related topics by translating the research objectives into readily accessible educational materials for middle-school students. This project will also provide funding to enable a graduate student and several undergraduate students to be trained in the techniques and perspectives of modern biology. Although numerous studies have investigated how polar diatoms are affected by varying light and iron, the cellular mechanisms leading to their distinct physiological responses remain unknown. Using comparative transcriptomics, the expression patterns of key genes and metabolic pathways in several ecologically important polar diatoms recently isolated from Antarctic waters and grown under varying iron and irradiance conditions will be examined. In addition, molecular indicators for iron and light limitation will be developed within these polar diatoms through the identification of iron- and light-responsive genes -- the expression patterns of which can be used to determine their physiological status. Upon verification in laboratory cultures, these indicators will be utilized by way of metatranscriptomic sequencing to examine iron and light limitation in natural diatom assemblages collected along environmental gradients in Western Antarctic Peninsula waters. In order to fully understand the role phytoplankton play in Southern Ocean biogeochemical cycles, dependable methods that provide a means of elucidating the physiological status of phytoplankton at any given time and location are essential.