Sawaki H, Sugiyama T, Omata T
Department of Applied Biological Sciences, School of Agricultural Sciences, Nagoya University, Japan.
Plant Cell Physiol. 1998 Jul;39(7):756-61. doi: 10.1093/oxfordjournals.pcp.a029431.
The cyanobacterium Synechococcus sp. strain PCC 7942 has duplicated phycocyanin subunit gene clusters cpcB1A1 and cpcB2A2, which are identical to each other and to those of Synechococcus sp. strain PCC 6301 (Anacystis nidulans). Nucleotide sequences of the 428 and 286 bases of the 5' non-coding regions of the cpcB1A1 and cpcB2A2 clusters, respectively, of strain PCC 7942 were identical to those of strain PCC 6301. As in strain PCC 6301, cpcB1A1 yielded two major transcripts of 1.4 and 1.3 kb and cpcB2A2 yielded a single transcript of 1.3 kb in strain PCC 7942. Thus, the structure and expression of cpcBA gene clusters in the two strains are essentially the same. Using bacterial luciferase encoded by luxAB as a reporter, cpcB1A1 was shown to have two promoters corresponding to the two major transcripts. Luminescence from the Synechococcus reporter strains carrying the fusions of the cpcBA promoters to luxAB showed circadian oscillation. Similar to the promoter of psbA1 encoding the D1 protein of PSII, the two cpcB1A1 promoters and the cpcB2A2 promoter showed the peak of activity at the end of the subjective day and the trough at the end of the subjective night.
蓝藻聚球藻属菌株PCC 7942具有重复的藻蓝蛋白亚基基因簇cpcB1A1和cpcB2A2，它们彼此相同，并且与聚球藻属菌株PCC 6301（集胞藻）的相同。PCC 7942菌株的cpcB1A1和cpcB2A2基因簇5'非编码区的428和286个碱基的核苷酸序列与PCC 6301菌株的相同。与PCC 6301菌株一样，在PCC 7942菌株中，cpcB1A1产生1.4和1.3 kb的两个主要转录本，cpcB2A2产生1.3 kb的单个转录本。因此，这两个菌株中cpcBA基因簇的结构和表达基本相同。使用luxAB编码的细菌荧光素酶作为报告基因，显示cpcB1A1有两个对应于两个主要转录本的启动子。携带cpcBA启动子与luxAB融合体的聚球藻报告菌株的发光显示出昼夜振荡。与编码PSII的D1蛋白的psbA1启动子类似，两个cpcB1A1启动子和cpcB2A2启动子在主观日结束时显示活性峰值，在主观夜结束时显示活性低谷。
