Molecular analysis of UV-A resistant operon in a marine cyanobacterium.

丝状蓝藻颤藻NKBG 091600能在白色光的UV-A辐射下生长。蓝细菌在细胞中产生生物蝶呤糖苷，即UV-A吸收化合物，这取决于UV-A照射。本文对蓝藻耐UV-A生长的分子机制进行了研究。在UV-A辐射的生长下，在辐射后8小时高表达60 kDa的蛋白。该蛋白的表达伴随着生物喋呤-葡萄糖苷量的增加。N-末端氨基酸序列的60 kDa的蛋白是同源的蓝藻GroEL，这是众所周知的热休克蛋白在各种生物。北方杂交分析表明，groEL mRNA的表达量随UV-A辐射的增强而增加，表明GroEL的诱导是由于转录水平的激活。利用PCR技术克隆了蓝细菌中含有GroESL操纵子（GroES+GroEL）的基因组DNA片段， 关于我们 根据报道的蓝藻引物设计引物。通过对基因结构的详细分析，发现CIRCE（Controlled Inverted Repeat of Chaperone Expression）区域位于GroES的上游，且CIRCE与GroES之间的距离是Synechococcus PCC 7942和Synechocystis PCC 6803的两倍。在CIRCE和GroES之间还发现了一个SOS盒状区域，而在聚球藻PCC 7942和集胞藻PCC 6803中没有发现。SOS盒样区域在大肠杆菌细胞中起SOS调节剂的作用。这些基因组结构上的差异表明，与其他蓝藻相比，耐UV-A蓝藻中GroESL的表达受到复杂的调控。除了生物蝶呤糖苷和GroEL的增加，还发现在UV-A耐受性蓝藻中粘叶黄素增加。蓝细菌的UV-A耐受性导致至少包含三个因素的复杂机制，（1）诱导生物喋呤-糖苷产生，（2）诱导GroESL转录，和（3）积累类胡萝卜素和叶黄素。今后需要开展研究，以开发创造耐紫外线A生物体的技术。少

A filamentous cyanobacterium Oscillatoria NKBG091600 can grow under UV-A irradiation with white light. The cyanobacterium produces biopterin-glycoside, UV-A absorbing compound, in the cell depending on the UV-A irradiation. In this report, molecular mechanisms of the UV-A tolerant growth of the cyanobacterium were studied. Under the growth of UV-A radiation, a protein of 60 kDa was highly expressed at 8 hours after irradiation. The expression of this protein was accompanied by an increase of biopterin-glucoside amount. N-terminal amino acid sequence of the 60 kDa protein was homologous to cyanobacterial GroEL which was known well as a heat shock protein in various organisms. Northern hybridization analysis showed that the level of groEL mRNA increased depending on the UV-A irradiation, showing that the induction of GroEL was due to the activation of transcription level. A genomic DNA fragment containing the GroESL operon (GroES+GroEL) in the cyanobacterium was cloned by using PCR with … More primers designed from those reported from cyanobacteria. By a detailed analysis of the gene structure, CIRCE (Controlled Inverted Repeat of Chaperone Expression) region was found at upper stream of GroES, while the distance between the CIRCE and GroES were two-fold longer than those in Synechococcus PCC 7942 and Synechocystis PCC 6803. A SOS box-like region was also found between the CIRCE and GroES.It was not found in Synechococcus PCC 7942 and Synechocystis PCC 6803. The SOS box-like region functioned as SOS regulator in E.coli cells. These differences in genome structure indicated that expression of GroESL iut the UV-A tolerant cyanobacterium was regulated by complex way comparing from those in other cyanobacteria. In addition to the increase of biopterin-glycosides and GroEL, myxoxanthophyll was also found to increase in the UV-A tolerant cyanobacterium. UV-A tolerance of the cyanobacterium resulted on complex mechanism containing at least three factors, (1) induction of biopterin-glycoside production, (2) induction of GroESL transcription, and (3) accumulation of carotenids and xanthophylls. Future studies will be required for developing the techniques for creation of UV-A tolerant organisms. Less