Marine Biotech. Fellowship: Regulation of Seaweed Photosynthesis by Temperature

海洋大型藻类在不同温度下生长时，表现出光合作用代谢的表型反应。这种热习服涉及细胞中光合酶和色素含量的变化，使海藻在一定的生长温度范围内保持类似的光限制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，但人们对温度对光化学装置组织的影响(例如，叶绿素-色素复合体的数量和大小)或调节热习服的过程知之甚少。该项目将允许戴维森博士于1993年在布鲁克黑文国家实验室的P.G.Falkowski博士和马里兰大学的E.Gantt博士的实验室里工作一年，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关于光合作用的热习服的下列问题。1.热驯化是如何在分子水平上调节的(如转录或翻译)？2.热驯化反应发生的速度有多快。3.热习服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比以及捕光叶绿素蛋白复合体内能量转移的大小和效率？4.热驯化和光驯化之间的表面相似性是否表明它们受到相同的机制调节？特别是，这个项目将检验热适应和光适应都受细胞能量收支调节的假设。所使用的技术包括：(I)用于测量细胞含量和合成(转录)信使核糖核酸的速率的抗体和cDNA探针，该信使核糖核酸编码光合作用装置的关键蛋白质以及这些蛋白质的含量和合成(翻译)；(2)泵浦-探测荧光计和其他生物物理技术，以测量与光系统I和II有关的捕光天线的功能尺寸，并研究叶绿素-蛋白质复合体内部和之间的能量转移；以及(3)免疫细胞化学，以研究光化学装置的成分在类囊体膜上的定位。通过这项研究获得的信息应该会大大增加我们对使海藻在低温环境中获得高生产力的生理过程的理解。

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.