Marine Biotech. Fellowship: Regulation of Seaweed Photosynthesis by Temperature

海洋巨藻在不同生长温度下表现出光合代谢的表型响应。这种热驯化涉及光合酶和色素的细胞含量的变化，使海藻在一定的生长温度范围内保持相似的限光和光饱和光合作用速率。尽管这些反应无疑是海藻在低温环境中取得生物成功的主要原因，但对于温度对光化学装置的组织（例如叶绿素-色素复合物的数量和大小）的影响，或调节热适应的过程，我们知之甚少。该项目将允许戴维森博士在1993年花一年的休假时间在P. G. Falkowski博士（布鲁克海文国家实验室）和E. Gantt博士（马里兰大学）的实验室工作，学习现代分子、生化和生物物理技术。这些技术将被用来解决光合作用热驯化的以下问题。1. 热驯化是如何在分子水平上调控的（即转录或翻译）？2. 适应反应发生的速度有多快。3. 热驯化如何影响光化学装置的组织和功能？例如，温度如何影响光系统各组成部分的化学计量，以及光收获叶绿素蛋白复合物内能量转移的大小和效率？4. 热驯化和光驯化的明显相似性是否表明它们受相同的机制调节？特别是，本项目将检验热驯化和光驯化都受细胞能量收支调节的假设。使用的技术包括：(i)抗体和cDNA探针，用于测量光合机构关键蛋白质编码mRNA的细胞含量和合成（转录）速率以及这些蛋白质的含量和合成（翻译）；（二）泵探针荧光计和其他生物物理技术，以测量与光系统I和ii相关的光收集天线的功能大小，并研究叶绿素-蛋白质复合物内部和之间的能量转移；（三）免疫细胞化学，研究光化学装置成分在类囊体膜上的定位。通过这项研究获得的信息将大大增加我们对使海藻在低温环境中实现高生产率的生理过程的理解。

Marine macroalgae exhibit phenotypic responses of their photosynthetic metabolism when grown at different temperatures. This thermal acclimation involves changes in cellular contents of photosynthetic enzymes and pigments that enable seaweeds to maintain similar rates of light-limited and light-saturated photosynthesis over a range of growth temperatures. Although these responses are undoubtedly a major reason for the biological success of seaweeds in low temperature environments, little is known about either the effect of temperature on the organization of the photochemical apparatus (e.g., number and size of chlorophyll- pigment complexes), or the processes that regulate thermal acclimation. This project will permit Dr. Davison to spend a year's sabbatical in 1993 working in the laboratories of Dr. P. G. Falkowski (Brookhaven National Laboratory) and Dr. E. Gantt (university of Maryland) to learn modern molecular, biochemical and biophysical techniques. These techniques will then be used to address the following questions about thermal acclimation of photosynthesis. 1. How is thermal acclimation regulated at the molecular level (i.e., transcription or translation)? 2. How rapidly does the acclimation response occur. 3. How does thermal acclimation affect the organization and function of the photochemical apparatus? For example, how does temperature affect the stoichiometry of the various components of the photosystems and the size and efficiency of energy transfer within the light- harvesting chlorophyll protein complexes? 4. Does the apparent similarity between thermal acclimation and photoacclimation indicate that they are regulated by the same mechanism? In particular, this project will test the hypothesis that thermal acclimation and photoacclimation are both regulated by the cellular energy budget. The techniques used will include: (i) antibodies and cDNA probes for measuring the cellular content and rates of synthesis (transcription) of mRNA that codes for the key proteins of the photosynthetic apparatus and contents and synthesis (translation) of these proteins, (ii) a pump-probe fluorometer and other biophysical techniques to measure the functional size of the light-harvesting antennae associated with photosystems I and II and to study energy transfer within and between chlorophyll-protein complexes, and (iii) immunocytochemistry to study the localization of components of the photochemical apparatus on the thylakoid membranes. The information obtained through this research should substantially increase our understanding of the physiological processes that enable seaweeds to achieve high rates of productivity in low temperature environments.