Genetic Analysis of Complementary Chromatic Adaptation

95-13576格罗斯曼藻胆体是一种捕光复合体，在真核红藻和原核蓝藻中都存在，可构成高达40%的细胞蛋白质。许多丝状蓝藻可以通过改变藻胆体的多肽和生色团组成来适应不同波长的光，从而使复合体更有效地吸收环境中普遍存在的波长的光；这个过程被称为互补颜色适应。我们已经分离到丝状蓝藻Fremyella diplosiphon的几个突变体，它们表现出异常的互补显色适应。其中一个突变体(红色突变体或FDR)的互补导致了rcaC的分离，这是一个编码颜色适应的关键调节基因。RcaC与两个成分调控系统的调节器有相似之处，尽管它有两个而不是一个接收域(其中包含对蛋白质功能重要的天冬氨酸残基)。该项目的主要目标是通过鉴定光感受器(S)和光响应信号转导链的组成部分来阐明控制颜色适应的机制。光感受器(S)和信号转导链中的一些元件可能与真核藻类和陆地植物中的光调控系统具有功能和进化关系。具体地说，我们将完成RcaC在接收域的每个或两个天冬氨酸中发生改变的菌株的表征(波长和强度依赖的反应)。此外，我们将确定补充其他具有异常颜色适应能力的菌株的基因的特征。一个没有互补颜色适应的突变体得到了一个基因的补充，该基因编码了一种与光敏色素有一些相似的蛋白质。这表明高等植物的光敏色素感受器可能是由蓝藻感光器进化而来的。对在颜色适应中补充突变体的基因的分析应该使我们能够确定信号转导链中的元件以及这些元件相互作用的方式。最后，我们将继续使用体内和体外的方法来分析红光激活的cpcB2A2基因集(编码藻蓝蛋白多肽)和绿光激活的cpeBA基因集(编码藻红蛋白多肽)的启动子区域，并正在开发策略来确定在颜色适应过程中参与控制细胞对光质量和强度的反应的顺式和反式作用因子。这项研究将帮助我们了解光是如何影响光合作用有机体的生长和发育的。了解光如何改变光合作用有机体的过程，可能使我们能够根据特定的光环境来定制植物。***

95-13576 Grossman The phycobilisome, a light-harvesting complex in both eukaryotic red algae and prokaryotic cyanobacteria, can constitute up to 40% of the cellular protein. A number of filamentous cyanobacteria can acclimate to different wavelengths of light by altering the polypeptide and chromophore composition of the phycobilisome, thereby making the complex more effective in absorbing the prevalent wavelengths of light in the environment; this process is called complementary chromatic adaptation. We have isolated several mutants of the filamentous cyanobacterium Fremyella diplosiphon that exhibit aberrant complementary chromatic adaptation. Complementation of one of these mutants (red mutant or FdR) led to the isolation of rcaC, a gene that encodes a key regulator of chromatic adaptation. RcaC has similarities to regulators of two component regulatory systems, although it has two rather than one receiver domain (which contains the aspartate residue important for the function of the protein). The main goal of the project is to elucidate the mechanisms that govern chromatic adaptation by identifying the photoreceptor(s) and components of the light-responsive signal transduction chain. The photoreceptor(s) and some of the elements of the signal transduction chain are likely to bear functional and evolutionary relationships to photoregulatory systems in eukaryotic algae and land plants. Specifically, we will complete the characterization (both wavelength-and intensity-dependent responses) of strains in which RcaC has been altered in each or both of the aspartates of the receiver domains. Furthermore, we will characterize the genes that complement additional strains that have aberrant chromatic adaptation. One mutant that exhibits no complementary chromatic adaptation has been complemented by a gene that encodes a protein that has some similarity to phytochrome. This suggest that the phytochrome photoreceptor of higher plants may have evolved from cyanobacterial photoreceptors. Analy ses of the genes that complement mutants in chromatic adaptation should enable us to define elements of the signal transduction chain and the ways in which the element interact. Finally, we will continue to use both in vivo and in vitro methods to analyze the promoter region of the red light-activated cpcB2A2 gene set (encoding phycocyanin polypeptides) and the green light-activated cpeBA gene set (encoding phycoerythrin polypeptides), and are developing strategies to define both cis and trans acting factors that are involved in controlling cellular responses to both light quality and intensity during chromatic adaptation. %%% The research will help us understand how light affects the growth and development of photosynthetic organisms. An understanding of how light modifies processes in photosynthetic organisms may enable us to tailor plants to specific light environments. ***