Abada E M, Balzer A, Jäger A, Klug G
Institut für Mikrobiologie und Molekularbiologie, Universität Giessen, Heinrich-Buff-Ring 26-32, Germany.
Mol Genet Genomics. 2002 Apr;267(2):202-9. doi: 10.1007/s00438-002-0652-y. Epub 2002 Mar 2.
Expression of the puf and puc operons, which encode proteins of the photosynthetic apparatus of Rhodobacter capsulatus, is regulated by oxygen. A drop in the oxygen tension in the environment leads to an increase in the levels of puf and puc mRNAs. In strains lacking bacteriochlorophyll (Bchl) due to mutations in bch genes, the rise in puf and puc mRNA levels observed on reduction of oxygen tension is much less pronounced than in wild-type cells, indicating co-regulation of the syntheses of pigments and pigment-binding proteins. Here we show that Bchl synthesis also affects the expression of the bchC gene, which codes for a subunit of bacteriochlorophyll synthase, suggesting an autoregulatory mechanism for the Bchl biosynthetic pathway. Furthermore, our data provide evidence that the RegB/RegA two-component system, which is known to play a central role in oxygen-controlled expression of photosynthesis genes, is also involved in the Bchl-dependent regulation. Mutant strains which do not synthesize RegB or RegA show similar oxygen-dependent puf and puc expression in the presence and absence of Bchl. Our results support the view that the RegB/RegA system can directly or indirectly sense whether Bchl synthesis takes place or not.
编码荚膜红细菌光合机构蛋白质的puf和puc操纵子的表达受氧调控。环境中氧张力的下降导致puf和puc mRNA水平升高。在由于bch基因突变而缺乏细菌叶绿素（Bchl）的菌株中，氧张力降低时观察到的puf和puc mRNA水平的升高比野生型细胞中要少得多，这表明色素和色素结合蛋白的合成存在共同调控。在这里，我们表明Bchl的合成也影响编码细菌叶绿素合酶一个亚基的bchC基因的表达，这表明Bchl生物合成途径存在一种自我调节机制。此外，我们的数据提供了证据，表明已知在光合作用基因的氧控制表达中起核心作用的RegB/RegA双组分系统也参与了Bchl依赖性调控。不合成RegB或RegA的突变菌株在有和没有Bchl的情况下表现出类似的氧依赖性puf和puc表达。我们的结果支持这样一种观点，即RegB/RegA系统可以直接或间接感知Bchl合成是否发生。
