Collaborative Research: Regulation of the C4-CO2 Concentrating Mechanism in Marine Diatoms by CO2, Light and Nutrients

最近发表的研究表明，海洋硅藻通过光合作用（即基于4碳中间体化合物，而不是基于3碳中间体的C3途径）利用C4途径浓缩二氧化碳（CO2）进行固定。该项目的目标是研究这一机制在海洋硅藻光合碳固定适应低二氧化碳中的作用，以及光和营养限制对这种适应的调节。在短期实验、光-暗循环、限光和限氮培养中，对模式硅藻C4基因转录物丰度和酶活性进行定量分析。野外工作将侧重于检查C4浓缩机制的重要性及其在俄勒冈海岸上升流地区的二氧化碳调节，该地区的特点是自然的二氧化碳浓度范围很广。田间实验方法将是测量天然硅藻种群中光合作用固碳对C4酶抑制的敏感性，以及与原位和操纵CO2浓度的关系。二氧化碳对海洋硅藻固碳的调节以及光和营养物对二氧化碳控制的调节可能会影响海洋生产力、地表水的生物碳输出，从而影响硅藻对全球碳循环的贡献，以及浮游植物的物种组成。这项研究的结果将对研究初级生产控制和生物碳泵的海洋学家，对利用硅藻有机物中的稳定碳同位素来了解当前和历史生产力和气候变化感兴趣的地球化学家，以及对浮游植物群落结构和进化感兴趣的海洋生态学家感兴趣。该项目将支持和培训一名研究生，并为本科生提供研究机会。研究人员还将把来自美国国家科学基金会资助的RIOS暑期实习项目的本科生纳入该项目，并将支持新成立的中大西洋海洋科学教育卓越中心的公共宣传和教育工作。

Recent published work presented evidence that marine diatoms use a C4 pathway to concentrate carbon dioxide (CO2) for fixation through photosynthesis (i.e. based on 4-carbon intermediate compounds, as opposed to a C3 pathway based on 3-carbon intermediates). The goal of this project is to examine the role of this mechanism in the acclimation of photosynthetic carbon fixation in marine diatoms to low CO2, and the modulation of this acclimation by light and nutrient limitation. Laboratory experiments will focus on quantifying C4 gene transcript abundances and enzyme activities in short-term experiments and in light-dark cycle and light- and nitrogen-limited cultures of model diatom species. Fieldwork will focus on examining the importance of the C4 concentrating mechanism and its regulation by CO2 in an upwelling region off the coast of Oregon characterized by a naturally wide range of CO2 concentrations. The field experimental approach will be to measure the sensitivities of photosynthetic carbon fixation in natural diatom populations to the inhibition of C4 enzymes, in relation to in situ and manipulated concentrations of CO2. The regulation of carbon fixation in marine diatoms by carbon dioxide (CO2) and the modulation of CO2 control by light and nutrients may affect ocean productivity, biological carbon export from surface waters and therefore the contribution of diatoms to global carbon cycling, and phytoplankton species composition. The results of this research will be of interest to oceanographers studying the controls of primary production and the biological carbon pump, geochemists interested in the use of stable carbon isotopes in diatom organic matter to understand current and historic productivity and climate change, and marine ecologists interested in the structure and evolution of phytoplankton communities. The project will support and train a graduate student as well as provide research opportunities for undergraduates. The researchers will also incorporate undergraduate students from the NSF-funded RIOS summer internship program into this project and will support the public outreach and education efforts of the newly established Mid-Atlantic Center for Ocean Science Education Excellence.