REGULATION OF GENES ENCODING PHYCOBILISOME POLYPEPTIDES

藻胆体是蓝藻的主要捕光复合体， 一些真核藻类。该复合体包括两种色素蛋白 (藻胆蛋白)和非色素蛋白(连接蛋白)。这个 真核藻中的藻胆蛋白是在叶绿体中合成的 而非色素连接蛋白是在细胞质中合成的 (并且必须导入细胞器)。因为亚基中的亚基 不同的藻胆蛋白是相关的，它们被认为代表一种 基因家族定位于叶绿体DNA。最近，一个编码该基因的 藻蓝蛋白的β亚基被放置在小的单拷贝区域 (该区域编码至少一个额外的藻胆蛋白亚基) 矛盾蓝藻的叶绿体基因组。我们建议找出另一个 藻胆蛋白亚基(阿尔法藻蓝蛋白和阿尔法和贝塔 别藻蓝蛋白)，确定这些基因是否 单独转录或作为一个单位转录，并生成特定的探针 鉴定蓝藻中的相似基因。几种化合物的合成 蓝藻中的藻胆蛋白亚基受光调控 (互补色适应)，而这一规定可在 转录水平。本研究利用C。 Paradoxa将使我们能够识别这些光调控的藻胆蛋白 基因和分析参与互补染色的分子事件 适应。关于RNA差异杂交的实验 从不同光质下生长的蓝藻中分离到克隆 蓝藻DNA银行，以及免疫技术，将 使我们能够鉴定合成藻胆体多肽的克隆，将 也有助于分离光调控的藻胆体基因。一次 这些基因被获得后，我们将在 蓝藻基因组(聚集或分散)，描述它们的特征 转录(尤其是对不同光线质量的反应)和 对它们的5‘端进行测序，以建立可能是 光调控转录。

Phycobilisomes are major light harvesting complexes in cyanobacteria and some eukaryotic algae. The complex includes both pigmented proteins (phycobiliproteins) and nonpigmented proteins (linker proteins). The phycobiliproteins in eukaryotic algae are synthesized in the chloroplast while the nonpigmented linker proteins are synthesized in the cytoplasm (and must be imported into the organelle). Since the subunits among the different phycobiliproteins are related, they are thought to represent a gene family localized to the plastid DNA. Recently, a gene encoding the Beta subunit of phycocyanin has been placed on the small single copy region (this region encodes at least one additional phycobiliprotein subunit) of the plastid genome of Cyanophora paradoxa. We propose to locate the other phycobiliprotein subunits (Alpha phycocyanin and Alpha and Beta allophycocyanin) on the plastid genome, determine whether these genes are transcribed separately or as a unit, and generate specific probes for identifying analogous genes in cyanobacteria. The synthesis of several phycobiliprotein subunits in cyanobacteria is regulated by light (complementary chromatic adaptation), and this regulation may be at the transcriptional level. The probes generated from the plastid genome of C. paradoxa will enable us to identify these light-regulated phycobiliprotein genes and analyze the molecular events involved in complementary chromatic adaptation. Experiments involving differential hybridizations of RNA isolated from cyanobacteria grown in different light qualities to clone banks of cyanobacterial DNA, and immunological techniques which would enable us to identify clones synthesizing phycobilisome polypeptides, would also aid in the isolation of light-regulated phycobilisome genes. Once these genes are obtained, we will examine their arrangement on the cyanobacterial genome (clustered or dispersed), characterize their transcription (especially in response to different light qualities) and sequence their 5' ends to establish features which might be essential for light-regulated transcription.