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，海洋硅藻使用C4途径通过光合作用浓缩二氧化碳(CO2)(即基于4碳中间化合物，而不是基于3碳中间体的C3途径)。本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环境中的作用，以及光和营养限制对这种适应的调节作用。实验室实验将侧重于量化C4基因转录物丰度和酶活性，在短期实验和光暗循环以及模式硅藻物种的光和氮限制培养中。实地考察的重点将是研究C4浓缩机制的重要性，以及在俄勒冈州沿海上升流地区二氧化碳浓度自然范围较大时二氧化碳对其的调节作用。野外实验的方法将是测量自然硅藻种群中光合碳固定对C4酶抑制的敏感性，与现场和操纵的二氧化碳浓度有关。二氧化碳(CO2)对海洋硅藻固碳的调节以及光和营养物质对CO2控制的调节可能会影响海洋生产力、表层水生物碳输出，从而影响硅藻对全球碳循环的贡献，以及浮游植物的种类组成。这项研究的结果将对研究初级生产力和生物碳泵的控制的海洋学家、对利用硅藻有机质中的稳定碳同位素来了解当前和历史生产力和气候变化的地球化学家以及对浮游植物群落的结构和演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NSF资助的Rios暑期实习计划的本科生纳入这个项目，并将支持新成立的大西洋中部海洋科学教育卓越中心的公共宣传和教育努力。

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.