REGULATION OF GENES ENCODING PHYCOBILISOME POLYPEPTIDES

藻胆体是蓝藻中主要的捕光复合体， 一些真核藻类 该复合物包括色素蛋白质 （藻胆蛋白）和非色素蛋白（连接蛋白）。 的 真核藻类中的藻胆蛋白在叶绿体中合成 而非色素连接蛋白在细胞质中合成 (and必须输入细胞器）。 由于各分单位 不同的藻胆蛋白是相关的，它们被认为代表了 定位于质体DNA的基因家族。 最近，一个编码 藻蓝蛋白的β亚基被放置在小的单拷贝区域上， (this编码至少一个另外的藻胆蛋白亚基的区域） 奇异蓝藻的质体基因组。 我们建议找到另一个 藻胆蛋白亚基（α-藻蓝蛋白和α-和β-藻胆蛋白 别藻蓝蛋白）的质体基因组，确定这些基因是否 单独或作为一个单位转录，并产生特异性探针， 在蓝细菌中发现类似基因。 几个合成 蓝藻藻胆蛋白亚基受光调控 （互补色适应），这种调节可能是在 转录水平。 利用C. paradoxa将使我们能够识别这些光调节藻胆蛋白 基因，并分析参与互补染色质的分子事件 适应 RNA差异杂交实验 从生长在不同光质的蓝藻中分离出来， 蓝藻DNA库，以及免疫技术， 使我们能够鉴定合成藻胆体多肽的克隆， 也有助于光调节藻胆体基因的分离。 一旦 获得这些基因后，我们将检查它们在 蓝藻基因组（集群或分散），表征其 转录（特别是在响应不同的光质量）和 对它们的5'端进行测序，以建立可能对 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.