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)水域铁的富集性导致伪菱形藻(Pennate)硅藻的种子种群迅速繁殖。实验室和野外实验的最新发现表明，拟菱形藻类具有在强络合铁(III)上生长的能力，并且这种能力直接依赖于铜的有效性。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。与高亲和力铁吸收蛋白同源的基因在假单胞菌中被发现，并且应该存在于假菱形藻中。由于假单胞藻具有高亲和力铁吸收蛋白的推测基因，并且在正常的实验室培养条件下仍然很容易缺乏铁，这意味着假单胞菌的铁吸收系统是不完整的，或者是一些环境因素阻止了高亲和力铁吸收系统的诱导或限制了高亲和力铁吸收系统的功能，而不是假菱形藻的高效系统。因此，需要进行更多的分子和生理研究，以更好地确定真核硅藻(如假单胞藻和假菱形藻)中高亲和力铁吸收系统的机制和功能。在这项研究中，加州大学圣克鲁斯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分子、生物介导性反应之间的关系，这些反应使铁可供真核浮游植物吸收。科学家小组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在假单胞菌中起作用，以及是否存在相同的成分并在假菱形藻中发挥作用。研究人员还将研究铁胁迫如何诱导高亲和力铁吸收同系物的基因表达模式，以及这些蛋白的存在如何与假菱形藻的铁和铜吸收速率相关。和假单胞菌(T.pustonana)。此外，这项工作将确定哪些细胞部分含有这一额外的铜配额，以及铁胁迫下假菱形藻对铜的需求增加是否发生在近海水域的其他浮游植物物种中。这项工作将对理解影响大型硅藻吸收铁的机制控制以及洞察自然或人为向HNLC水域的铁通量如何影响碳向深海的出口和影响全球气候提供重要信息。就更广泛的影响而言，该项目将为一名初级女性调查员、一名博士生和一名研究生提供培训、教育和研究。一名将把实地成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.