Copper limitation and toxicity in marine diatoms

提案摘要： 公海的表层沃茨含有地球上任何环境中最低水平的微量金属，但由于灰尘和深层沃茨的涌升流的输入，会暂时暴露于高浓度。浓度的这些大的变化意味着生活在这些区域的光合微生物可以暴露于有时不足以生长和有时抑制的水平。铜是一种重要的微量金属，因为它是参与关键生化反应的酶和氧化还原蛋白质中的重要辅助因子，并且因为它是毒性最大的金属之一。然而，我们对铜如何影响硅藻的生长知之甚少，硅藻是生活在海洋中的一组重要的单细胞初级生产者，或者当环境中铜的可用性发生变化时，它们如何适应和适应。本研究提案的目的是：1）描述海洋和沿海硅藻的铜调节转录组并鉴定铜缺乏和毒性下差异表达的基因，2）量化铜吸收基因同源物的转录调节，3）测量细胞外铜还原并确定其在铜吸收中的作用，4）确定硅藻种源如何影响铜稳态，（5）开发与硅藻铜营养状态相关的分子标记，并应用于海洋铜的有效性评估。这项拟议中的研究是阐明调节浮游植物生长的因素的持续努力的一部分。它将提供一个机制的理解，铜在硅藻体内平衡，并确定潜在的生态和海洋地球化学后果的变化，铜的可用性在海洋中。这项工作是及时的，因为据预测，海洋酸化将大大增加某些无机铜物种的浓度，并影响铜络合作用。硅藻如何可能受到这些变化的影响是不确定的，因为我们对它们的铜吸收和解毒机制有初步的了解，对可用于细胞运输的铜物种的类型知之甚少。这里概述的研究将开始填补这些知识空白。

Summary of Proposal: Surface waters of the open sea contain some of the lowest levels of trace metals of any environment on Earth, yet are transiently exposed to elevated concentrations via inputs from dust and upwelling from deep waters. These large variations in concentration mean that the photosynthetic microbes living in these regions can be exposed to levels that are at times inadequate for growth and at other times inhibitory. Copper is an important trace metal because of its role as an essential co-factor in enzymes and redox proteins involved in key biochemical reactions and because it is one of the most toxic. Yet, we know little about how copper affects growth of diatoms, an important group of single-celled primary producers living in the sea, or the ways in which they acclimate and adapt when copper availability changes in the environment. The aims of this research proposal are: 1) to describe the copper-regulated transcriptome of an oceanic and coastal diatom and identify differentially expressed genes under copper deficiency and toxicity, 2) to quantify transcriptional regulation of copper uptake gene homologs, 3) to measure extracellular copper reduction and determine its role in copper uptake, 4) to determine how diatom provenance affects copper homeostasis, and 5) to develop molecular markers that correlate with the copper nutritional state of diatoms and apply them to assess copper availability in the ocean. The proposed research is part of a continuing effort to elucidate the factors regulating phytoplankton growth. It will provide a mechanistic understanding of copper homeostasis in diatoms and identify the potential ecological and biogeochemical consequences of variations in copper availability in the sea. The work is timely given that ocean acidification is predicted to greatly increase the concentration of some inorganic species of copper and affect copper complexation. How diatoms might be affected by these changes is uncertain as we have a rudimentary understanding of their mechanisms of copper uptake and detoxification and know little about the types of copper species that are available for cellular transport. The research outlined here will begin to fill these gaps in knowledge.