Modulation of the iron limitation response by silicate and light availability in Southern Ocean diatoms

铁、硅酸盐和光的供应被认为是南大洋浮游植物生长、群落组成以及相应地向深海输出物质的主要决定因素。硅藻，这一地区的主要浮游植物群体，已经制定了不同的适应策略，在这个高营养，低叶绿素（HNLC）地区强加给他们的独特挑战。这些适应性战略的几个方面可以理解为反映了优化总增长率之间的权衡（例如，高亲和力营养吸收系统、快速适应、高生长速率）与降低死亡率（缓慢生长、大尺寸、厚硅酸盐细胞壁）。在这个项目中，我建议调查代表这一连续体的两个极端：一个快速增长，快速适应的物种，已被证明能迅速响应铁此外（Chaetoceros debilis），和一个缓慢增长，但非常好的保护物种（Fragilariopsis kerguelensis）。这些物种的生长反应，操纵的营养和光的可用性进行了研究。高通量转录组学方法现在提供了一种可能性，以获得更深入的了解这些不同的适应性策略的细胞过程的细节。我建议应用深度转录组测序来表征这些物种对铁限制的基因表达反应，伴随着高或低的光照和硅酸盐的可用性。我假设上述两种不同的适应策略代表了不同的细胞调节网络，特别是硅酸盐的可用性调节细胞对铁限制的反应。这项建议补充了阿尔弗雷德-韦格纳研究所PACES方案内正在进行的工作（专题1：“变化中的北极和南极”，工作包4：“南极绕极气候和生态系统研究”），采用分子方法了解影响地球化学循环的进化生态学问题。

Availability of iron, silicate and light have been recognized as the major determinants of phytoplankton growth, community composition, and, accordingly, material export to depth in the Southern Ocean. Diatoms, the dominant phytoplankton group of this region, have developed diverse adaptation strategies to the unique challenges imposed upon them in this high nutrient, low chlorophyll (HNLC) region. Several aspects of these adaptive strategies can be understood as reflecting trade-offs between optimizing gross growth rates (e.g., high affinity nutrient uptake systems, quick acclimation, high growth rates) vs. reducing mortality rates (slow growth, large size, thick silicate cell walls). In this project, I propose to investigate representatives for two extremes of this continuum: a fast growing, fast acclimating species that has been shown to respond quickly to iron addition (Chaetoceros debilis), and a slowly growing, but extremely well protected species (Fragilariopsis kerguelensis). Growth responses of these species to manipulation of nutrient and light availability have been studied previously. High throughput transcriptomic methods now provide a possibility to gain deeper insights into details of the cellular processes underlying these different adaptive strategies. I propose to apply deep transcriptome sequencing for characterization of the gene expression responses of these species to iron limitation, accompanied by high or low light and silicate availability. I hypothesize that the two different adaptive strategies outlined above represent different cellular regulatory networks, and that, in particular, silicate availability modulates cellular responses to iron limitation. This proposal complements ongoing work within the PACES programme of the Alfred-Wegener- Institute (Topic 1: “The Changing Arctic and Antarctic”, workpackage 4: “Antarctic Circumpolar Climate and Ecosystem Study”) by applying molecular approaches for understanding questions of evolutionary ecology affecting biogeochemical cycles.