Transcriptional control of expression of genes for photosynthetic reaction center and light-harvesting proteins in the purple bacterium Rhodovulum sulfidophilum
Transcriptional control of expression of genes for photosynthetic reaction center and light-harvesting proteins in the purple bacterium Rhodovulum sulfidophilum
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DOI：
10.1128/jb.182.10.2778-2786.2000
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发表时间：
2000-05-01
影响因子：
3.2
通讯作者：
Matsuura, K
中科院分区：
文献类型：
--
作者：
Masuda, S;Nagashima, KVP;Matsuura, K
紫色光合细菌Rhodovulum sulfidophilum即使在黑暗中高度通气的条件下也能合成光合器官。为了理解光合基因的非氧依赖性表达，分析了编码捕光蛋白1和反应中心蛋白的psf操纵子的表达。北方印迹杂交分析表明，puf mRNA的合成没有显着抑制氧在该细菌。puf mRNA转录起始位点的高分辨率5'定位和puf上游调控区的DNA序列分析表明，puf操纵子表达有三个可能的启动子，其中两个与Rhodobacter capsulatus的启动子具有高度的序列相似性，这表明高水平的氧抑制光系统合成。缺失分析表明，第三个启动子是氧非依赖性的，但该启动子的活性不足以解释mRNA的有氧水平。氧对转录后puf mRNA的降解无明显影响。嗜硫菌从这些结果中，我们得出结论，在嗜硫红球菌中puf操纵子的表达受到氧的微弱抑制，这可能是由于以下原因：（i）puf操纵子转录有三个启动子，其中至少一个是氧非依赖性的;（ii）可能不受氧影响的通读转录物在维持puf mRNA水平方面可能是重要的;和（iii）puf mRNA即使在需氧条件下也相当稳定。
The purple photosynthetic bacterium Rhodovulum sulfidophilum synthesizes photosynthetic apparatus even under highly aerated conditions in the dark. To understand the oxygen-independent expression of photosynthetic genes, the expression of the psf operon coding for the light-harvesting 1 and reaction center proteins was analyzed. Northern blot hybridization analysis showed that puf mRNA synthesis was not significantly repressed by oxygen in this bacterium. High-resolution 5' mapping of the puf mRNA transcriptional initiation sites and DNA sequence analysis of the puf upstream regulatory region indicated that there are three possible promoters for the puf operon expression, two of which have a high degree of sequence similarity with those of Rhodobacter capsulatus, which shows a high level of oxygen repression of photosystem synthesis. Deletion analysis showed that the third promoter is oxygen independent, but the activity of this promoter was not enough to explain the aerobic level of mRNA. The posttranscriptional puf mRNA degradation is not significantly influenced by oxygen in R. sulfidophilum. From these results, we conclude that puf operon expression in R sulfidophilum is weakly repressed by oxygen, perhaps as a result of the following: (i) there are three promoters for puf operon transcription, at least one of which is oxygen independent; (ii) readthrough transcripts which may not be affected by oxygen may be significant in maintaining the puf mRNA levels; and (iii) the puf mRNA is fairly stable even under aerobic conditions.