Light/Shade Adaptation of Prochlorothrix Hollandica

这项工作的理由是， 光合生物必须适应环境的变化 光强度，以最大限度地提高光合效率。 在强光下，多余的能量必须消散，以防止 光损伤，而在低光下，光子捕获已被最大化 使光合作用有效进行。 我们一直 研究光合原核生物原绿丝菌 hollandica，作为一个模型系统来检查光/影 光合机构的适应。 这种细菌 非常适合这些研究，因为它在结构上类似于 高等植物叶绿体，但可以在实验室中操作， 比高等植物或真核藻类更容易。 我们的工作 描述了在光/影适应过程中发生的事件 在P. hollandica和植物叶绿体中，我们已经证明 两个系统都有类似的机制。 总的来说，我们 我相信，分析P. hollandica的这一过程将揭示 更详细地描述了植物处理 环境光强度的变化。 %%% 具体来说，我们的工作表明，光/影适应 部分涉及两个独立事件的相互作用。 第一、 当转向强光时， 系统将在大约30分钟内重新组织;我们 计算出40%的辅助叶绿素 改变它们的方向， 转移在强光下改变。 这种机制似乎是 由光激活蛋白激酶控制。 第二，作为细胞 经历强光几个小时，光激活 金属蛋白酶活性降解附件的子集 叶绿素结合蛋白 这种蛋白酶的功能是 很可能是为了限制在高温下的光子捕获量， 辐照度 准确理解 细胞感知强光并触发这些反应将帮助我们 了解光合作用是如何在叶绿体（植物）中调节的 系统. 迄今为止，我们已经克隆了许多编码 参与这些机制的成分;这些包括基因 编码蛋白激酶。 我们目前正在研究如何 光会影响这些基因的表达， 激酶的功能和组织的影响， 光合捕光天线 最后，我们 详细研究蛋白水解活性如何破坏 辅助叶绿素蛋白在强光下;这是可能的 辅助叶绿素蛋白是 通过类囊体蛋白磷酸化的蛋白水解 激酶。

The rationale for this work is based on the fact that all photosynthetic organisms must adapt to changes in environment light intensity in order to maximize photosynthetic efficiency. At high light, excess energy has to be dissipated to prevent photodamage, while at low light, photon capture has be maximized to allow photosynthesis to proceed efficiently. We have been studying the photosynthetic prokaryote, Prochlorothrix hollandica, as a model system to examine the light/shade adaptation of the photosynthetic apparatus. This bacterium is well-suited to these studies because it is structurally similar to higher plant chloroplasts, but can be manipulated in the lab more easily that higher plants or eukaryotic algae. Our work has characterized the events occurring during light/shade adaptation in both P. hollandica and plant chloroplasts, and we have shown that similar mechanisms occur in both systems. Overall, we believe that analyzing this process in P. hollandica will reveal in more detail the pathway required for plants to handle alterations in environmental light intensity. %%% Specifically, our work has shown that light/shade adaptation involves in part the interplay of two separate events. First, upon a shift to high light, the overall chlorophyll pigment system becomes reorganized in approximately 30 minutes; we calculate 40% of the accessory chlorophyll pigments are capable of changing their orientation such that energy capture and transfer is altered at high light. This mechanism appears to be controlled by a light-activated protein kinase. Second, as cells experience high light for several hours, a light-activated metalloprotease activity degrades a subset of the accessory chlorophyll-binding proteins. The function of this protease is probably to limit the amount of photon capture at high irradiances. Understanding precisely the mechanism(s) by which cells sense high light and trigger these responses will help us understand how photosynthesis is regulated in chloroplast (plant) systems. To date, we have cloned many of the genes encoding the components involved in these mechanisms; these include the genes encoding the protein kinase. We are currently examining how light affects the expression of these genes, and how the function of the kinase affects the function and organization of the photosynthetic light-harvesting antenna. Lastly, we are examining in detail how the proteolytic activity acts to destroy the accessory chlorophyll-proteins in high light; it is possible that the accessory chlorophyll-proteins are targeted for proteolysis by their phosphorylation by the thylakoid protein kinase.