Collaborative Research: Antarctic Diatom Proteorhodopsins: Characterization and a Potential Role in the Iron-limitation Response

视紫红质是一种嵌入细胞膜的蛋白质，它可以作为光驱动的质子泵产生代谢和生长所需的能量。蛋白视紫红质在多种海洋原核微生物中的发现引发了对其分布和功能作用的广泛研究。 最近，在硅藻中发现了一种质子泵，类似视紫红质的基因，硅藻是一种海洋浮游植物，在南大洋的大部分食物网中占主导地位。从那时起，蛋白视紫质已被确定在许多，但不是所有的硅藻物种。 Proteorhodopsin基因在生活在寒冷、铁有限的海洋区域（包括南大洋）的硅藻中比在其他区域的硅藻中更常见。据认为，变形视紫红质特别适合在南大洋使用能源生产，因为它不使用铁，其反应速率对温度不敏感（不像传统的光合作用）。该项目的总体目标是确定南极硅藻蛋白视紫质的特征，并确定其在这些硅藻适应南极沃茨低铁浓度和极低温度方面的作用。这项研究将提供有关南大洋硅藻成功的遗传基础的新信息，以及这种独特的分子如何在为南极食物网提供能量方面发挥关键作用。 更广泛的影响活动旨在通过将研究目标转化为中学生易于获得的教育材料来促进极地海洋科学相关主题的教学。该项目将联合收割机结合分子、生物化学和生理学测量，以确定南极西部半岛地区硅藻分离物中蛋白视紫质的作用和重要性。将确定蛋白质视紫红质的质子泵送特性和泵送速率作为光强度和温度的函数、所得蛋白质视紫红质连接的细胞内ATP产生速率以及蛋白质的细胞定位。该项目将研究南极洲β-变形视紫红质表达最高的环境条件，并构建一个细胞能量预算，其中包括在这些不同环境条件下生长的β-变形视紫红质。 估计的能量通量产生的蛋白视紫红质将比较总能量产生的光合光反应和代谢耦合呼吸速率。最后，南极硅藻和含蛋白视紫质的硅藻分离物从温带地区的特点和基因表达的β-Proteorhodopsin将进行比较，以确定是否有一个优先依赖能源生产通过蛋白视紫质在硅藻居住在寒冷的，铁有限的地区的海洋。教育活动将与莫尔黑德天文馆和科学中心合作进行，该中心负责协调SciVentures项目，这是一个面向查佩尔山及周边地区中学生的热门夏令营。 研究人员将与天文馆合作，为SciVentures的参与者开发以浮游植物及其在极地海洋食物网中发挥的重要作用为重点的活动。此外，还将为教室开发一个关于南极浮游植物的教学模块，并将其提供给教育网络网站，并在全国科学教育工作者的讲习班上提出。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

Proteorhodopsins are proteins that are embedded in membranes that can act as light-driven proton pumps to generate energy for metabolism and growth. The discovery of proteorhodopsins in many diverse marine prokaryotic microbes has initiated extensive investigation into their distributions and functional roles. Recently, a proton-pumping, rhodopsin-like gene was identified in diatoms, a group of marine phytoplankton that dominates the base of the food web in much of the Southern Ocean. Since this time, proteorhodopsins have been identified in many, but not all, diatom species. The proteorhodopsin gene is more frequently found in diatoms residing in cold, iron-limited regions of the ocean, including the Southern Ocean, than in diatoms from other regions. It is thought that proteorhodopsin is especially suited for use energy production in the Southern Ocean since it uses no iron and its reaction rate is insensitive to temperature (unlike conventional photosynthesis). The overall objective of the project is to characterize Antarctic diatom-proteorhodopsin and determine its role in the adaptation of these diatoms to low iron concentrations and extremely low temperatures found in Antarctic waters. This research will provide new information on the genetic underpinnings that contribute to the success of diatoms in the Southern Ocean and how this unique molecule may play a pivotal role in providing energy to the base of the Antarctic food web. Broader impact activities are aimed to promote the teaching and learning of polar marine-sciences related topics by translating research objectives into readily accessible educational materials for middle-school students.This project will combine molecular, biochemical and physiological measurements to determine the role and importance of proteorhodopsin in diatom isolates from the Western Antarctic Peninsula region. Proton-pumping characteristics and pumping rates of proteorhodopsin as a function of light intensity and temperature, the resultant proteorhodopsin-linked intracellular ATP production rates, and the cellular localization of the protein will be determined. The project will examine the environmental conditions where Antarctic diatom-proteorhodopsin is most highly expressed and construct a cellular energy budget that includes diatom-proteorhodopsin when grown under these different environmental conditions. Estimates of the energy flux generated by proteorhodopsin will be compared to total energy generation by the photosynthetic light reactions and metabolically coupled respiration rates. Finally, the characteristics and gene expression of diatom-proteorhodopsin in Antarctic diatoms and a proteorhodopsin-containing diatom isolates from temperate regions will be compared in order to determine if there is a preferential dependence on energy production through proteorhodopsin in diatoms residing in cold, iron-limited regions of the ocean. Educational activities will be performed in collaboration with the Morehead Planetarium and Science Center who co-ordinates the SciVentures program, a popular summer camp for middle-school students from Chapel Hill and surrounding areas. In collaboration with the Planetarium, the researchers will develop activities that focus on phytoplankton and the important role they play within polar marine food webs for the SciVentures participants. Additionally, a teaching module on Antarctic phytoplankton will be developed for classrooms and made available to educational networking websites and presented at workshops for science educators nationwide.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.