Collaborative Research: The Role of Copper in the High Affinity Iron

亚北极太平洋高硝酸盐、低叶绿素（HNLC）水域的铁富集导致伪尼齐亚（pennate）硅藻种子种群迅速开花。最近来自实验室和野外实验的发现表明，伪nitzschia物种具有在强络合的Fe （III）上生长的能力，并且这种能力直接依赖于Cu的有效性。这种铁吸收系统是在铁胁迫下诱导的，其效率与已知的其他沿海硅藻形成对比。与高亲和力铁摄取蛋白同源的基因在假单胞菌中被发现，并且应该存在于伪尼茨氏菌物种中。由于假假单胞菌具有高亲和力铁摄取蛋白的基因，并且在正常的实验室培养条件下仍然可以很容易地缺乏铁，这意味着假单胞菌的铁摄取系统是不完整的，或者是某些环境因素阻止了高亲和力铁摄取系统的诱导或限制了其功能，而假尼茨氏菌的系统是高效的。因此，需要更多的分子和生理研究来更好地确定真核硅藻（如T. pseudonana和pseudonitzschia）高亲和力铁吸收系统的机制和功能。在这项研究中，加州大学圣克鲁兹分校和罗德岛大学的研究人员将重点了解海水中铁氧化还原化学与真核浮游植物吸收铁的分子生物学介导反应之间的关系。科学家团队将确定序列同源性表明的高亲和力铁摄取系统的结构成分是否可以在假假单胞菌中起作用，以及相同的成分是否存在并且可以在伪尼茨氏菌中起作用。研究人员还将研究高亲和力铁摄取同源物的基因表达模式如何被铁胁迫诱导。以及这些蛋白质的存在与伪尼茨氏菌和假单胞菌对铁和铜的吸收速率之间的关系。此外，该工作将确定哪些细胞部分拥有额外的Cu配额，以及在铁胁迫下伪nitzschia对Cu需求的增加是否与近海其他浮游植物一起发生。这项工作对于了解影响大型硅藻铁吸收的机制控制非常重要，同时也有助于深入了解自然或人为的铁通量如何影响向深海输出碳并影响全球气候。就更广泛的影响而言，该项目将为一名初级女研究员、一名博士生和一名研究生提供培训、教育和研究。一名将把实地研究结果带到科学课堂的高中教师也将参与该项目。

Iron enrichment of High Nitrate, Low Chlorophyll (HNLC) waters of the subarctic Pacific lead seed populations of Pseudo-nitzschia (pennate) diatoms to rapidly bloom. Recent findings from laboratory and field experiments show that Pseudo-nitzschia species posses the ability to grow on strongly complexed Fe (III), and that this ability is directly dependent on Cu availability. This Fe uptake system is induced under Fe-stress, and its efficiency contrasts what is known about other coastal diatoms. Genes homologous to high affinity Fe uptake proteins are found in T. pseudonana, and should be present in Pseudo-nitzschia species. Because T. pseudonana possesses putative genes for high-affinity Fe uptake proteins and can still be readily starved for Fe under normal laboratory culture conditions, it is implied that the Fe uptake system in T. pseudonana is incomplete, or that some environmental factor prevents induction or limits the functionality of the high affinity Fe uptake system in contrast to the highly efficient system in Pseudo-nitzschia. As a result, more molecular and physiological studies are needed to better ascertain the mechanism and functionality of the high affinity Fe uptake systems in eukaryotic diatoms such as T. pseudonana and Pseudo-nitzschia species. In this study, researchers at the University of California at Santa-Cruz and the University of Rhode Island will focus on understanding the relationship between Fe redox chemistry in seawater and the molecular, biologically mediated reactions that render Fe availability for uptake by eukaryotic phytoplankton. The team of scientists will establish whether or not the structural components of the high affinity Fe uptake system indicated by sequence homology can function in T. pseudonana and if the same components are present and can function in Pseudo-nitzschia spp. The researchers will also examine how the gene expression patterns of the high affinity iron uptake homologues are induced by Fe stress, and how the presence of these proteins correlates with the rates of Fe and Cu uptake in Pseudo-nitzschia spp. and T. pseudonana. In addition, the work will determine which cell fraction harbors this additional Cu quota and whether or not the increased Cu requirement of Pseudo-nitzschia under Fe stress occurs with other phytoplankton species in offshore waters. This work will be important to understanding the mechanistic controls that effect the Fe uptake of large diatoms, as well as provide insight into how the natural or anthropogenic fluxes of iron to HNLC waters influence the export of carbon to the deep ocean and effect the global climate. In terms of broader impacts, the project will provide the training, education, and research to a beginning female investigator, a Ph.D. student, and a graduate student. A high school teacher who will bring the field results to the science classroom will also participate in the project.