Dimensions: Links Between Spectral Irradiance and Cryptophyte Biodiversity in Environments from Ponds to Oceans

在水生环境中，被称为浮游植物的微小藻类是重要的初级生产者。通过光合作用，这些生物将二氧化碳固定到有机碳分子中，为池塘、河流、湖泊和海洋中的生命提供燃料。在不同的环境中，光的颜色是不同的，比如深蓝色的海洋和黑色的河流。为了在特定的环境中生存，浮游植物必须有光合色素来吸收可用的光的颜色。这个项目的重点是隐生植物，一种相对不常见的浮游植物群，它们大量存在于从小池塘到海洋的各种水生栖息地。隐生植物利用藻胆素色素捕获光能；这些色素允许隐生植物在其他类型的藻类很少利用的光环境中进行光合作用。该项目的目标是：(1)表征隐生植物物种的生态分布和分类多样性；(2)确定其在不同光环境下的光捕获有效性；(3)表征关键光捕获基因的分子进化途径。了解这些联系对于预测土地利用的变化（如森林砍伐和城市化，两者都会影响下游流域的光的颜色）将如何影响水生生产力非常重要。培养博士后1人，研究生2-4人，本科生10人。通过与莫里斯学院（Morris College）和南卡罗来纳大学（University of South Carolina）其他项目的合作，未被充分代表的少数族裔将被纳入暑期奖学金。新的隐菌菌株将储存在活的培养物中，供其他研究人员使用。这个项目的核心问题看似简单：相对于光环境，功能、遗传和系统发育多样性是如何在隐生植物的生态多样性中相互作用的？研究人员将对隐生植物的生物多样性进行综合研究，以了解在其历史多样化的背景下，光谱辐照度的环境变化如何与隐生植物的光捕获生理多样性相关。这项工作包括几个组成部分：(1)在小池塘到海洋的水体中进行实地采样，以确定菌株生活的特定光环境，确定隐生植物在这些栖息地产生的色素，并识别新物种；(2)表型研究，以确定光谱辐照度（光色）的变化如何影响不同分类群的光捕获、光合作用和生长。这些也将决定整个隐藻菌株中藻胆素的光谱吸收；(3)基于约200株菌株的核形态基因组测序构建了一个有良好支持的系统发育；(4)关键光捕获基因的分子进化分析，特别是那些编码隐植藻胆蛋白α和β亚基的基因，以及那些参与藻胆素合成途径的基因；(5)实验进化，测试不同隐生植物品系进化成新的光生态位的能力；(6)实验转录组学，鉴定不同菌株对光谱辐照度变化的功能响应；(7)栖息地、分子进化、生物性能和光谱吸收之间关系的系统发育测试。最终，这项工作应该对我们理解光合作用的多样化以及这种多样化在隐生植物生态分布中的作用做出革命性的贡献。

In aquatic environments, microscopic algae known as phytoplankton are important primary producers. Through photosynthesis, these organisms fix carbon dioxide into the organic carbon molecules that fuel life in ponds, rivers, lakes and oceans. The color of light available for photosynthesis varies among environments, e.g., the deep blue ocean vs. a black water river. In order to live in a particular environment, phytoplankton must have photosynthetic pigments that are tuned to absorbing the colors of light available. This project focuses on the cryptophytes, a relatively uncharacterized group of phytoplankton, that are abundant in a wide range of aquatic habitats ranging from small ponds to oceans. Cryptophytes use phycobilin pigments to capture light energy; these pigments allow cryptophytes to photosynthesize in light environments that are poorly exploited by other types of algae. The project goals are: (1) to characterize the ecological distribution and taxonomic diversification of cryptophyte species, (2) to determine the effectiveness of their light capture in different light environments, and (3) to characterize the molecular evolutionary pathways of critical light capture genes. Understanding these links is important to predicting how changes in land-use (like deforestation and urbanization, both of which impact the color of light in downstream watersheds) will affect aquatic productivity. This project will provide training for a post-doc, 2-4 graduate students, and 10 undergraduates. Through a partnership with Morris College and other University of South Carolina programs, underrepresented minorities will be recruited into summer fellowships. Novel cryptophyte strains will be deposited in living culture collections for use by other researchers. This project's central question is deceptively simple: How do functional, genetic, and phylogenetic diversity interact in the ecological diversification of cryptophytes with respect to light environment? The researchers will conduct an integrative research program on the biodiversity of cryptophytes to understand how environmental variation in spectral irradiance is associated with the physiological diversity of light capture in cryptophytes in the context of their historical diversification. This work integrates several components: (1) Field sampling in water bodies ranging from small ponds to oceans to identify the specific light environments in which strains live, to determine the pigments that cryptophytes produce in those habitats, and to identify novel species; (2) Phenotypic studies to determine how variation in spectral irradiance (light color) influences light capture, photosynthesis, and growth of diverse taxa. These will also determine spectral absorption of phycobilins in strains throughout the cryptophyta; (3) Construction of a well-supported phylogeny based on sequencing nucleomorph genomes of ~200 strains; (4) Analyses of molecular evolution of key light capture genes, in particular those that encode the alpha and beta subunits of the cryptophyte phycobiliproteins, and those involved in the phycobilin synthesis pathway; (5) Experimental evolution to test the ability of diverse strains of cryptophytes to evolve into new light niches; (6) Experimental transcriptomics to identify the functional responses of diverse strains to variation in spectral irradiance; and (7) Phylogenetically-informed tests of the associations between habitat, molecular evolution, organismal performance, and spectral absorbance. Ultimately, this work should be a transformative contribution to our understanding of the diversification of photosynthesis and the role of that diversification in the ecological distribution of cryptophytes.