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首页> 外文期刊>Journal of bacteriology >A New Circadian Class 2 Gene, opcA, Whose Product Is Important for Reductant Production at Night in Synechococcus elongatus PCC 7942
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A New Circadian Class 2 Gene, opcA, Whose Product Is Important for Reductant Production at Night in Synechococcus elongatus PCC 7942

机译：一个新的昼夜节律2类基因opcA，其产物对于延长Synechococcus elongatus PCC 7942中的夜间还原剂产生很重要

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Gene expression in the cyanobacterium Synechococcus elongatus PCC 7942 is under the control of a circadian oscillator, such that peaks and troughs of expression recur with a periodicity of about 24 h in the absence of environmental cues. This can be monitored easily as light production from luciferase gene fusions to S. elongatus promoters. All promoters seem to exhibit circadian oscillation of expression, but the phasing of peak and trough times differs among different genes. The majority of genes are designated class 1, with expression peaks near dusk or subjective dusk (the time corresponding to dusk in the absence of a diurnal cycle). A minority, of which purF is an example, have expression peaks approximately 12 h out of phase with class 1 genes. A screen of Tn5 mutants for those in whichpurF phasing is altered revealed a mutant that carries an insertion in the opcA gene, previously identified as essential for glucose-6-phosphate dehydrogenase function. However, a different enzymatic reporter and in vitro luciferase assays revealed that the expression pattern of the purF promoter is not altered by opcA inactivation, but rather the reduced flavin mononucleotide substrate of luciferase is limiting at the time of the natural circadian peak. The results suggest that OpcA is involved in temporally separated reductant-generating pathways in S. elongatus and that it has a role outside of its function in activating glucose-6-phosphate dehydrogenase. The opcAgene, expected to be cotranscribed with fbp andzwf, was shown to have its own class 2 promoter, whereas the fbp promoter was determined to be in class 1. Thus, opcA expression is likely to be constitutive by virtue of the activity of two promoters in nearly opposite circadian phases.
机译：蓝藻细菌PCC 7942中的基因表达受生物钟振荡器的控制，因此在没有环境提示的情况下，表达的高峰和低谷以约24小时的周期重复出现。从荧光素酶基因融合物到 S的光产生，可以很容易地进行监测。伸长启动子。所有启动子似乎都表现出昼夜节律性的振荡，但是不同基因之间的峰谷时间和谷峰时间的阶段有所不同。大多数基因被指定为1类，其表达峰接近黄昏或主观黄昏（时间对应于没有昼夜循环的黄昏）。少数族裔（其中以 purF 为例）的表达峰与1类基因异相约12 h。通过对Tn 5 突变体进行筛选，发现其中的 purF 相位改变了，该突变体在 opcA 基因中插入了一个插入物，该基因先前已确定对于6-磷酸葡萄糖脱氢酶功能至关重要。然而，不同的酶报告基因和体外荧光素酶测定表明， purF 启动子的表达模式不会因 opcA 失活而改变，而是荧光素酶的黄素单核苷酸底物减少在自然昼夜节律高峰时受到限制。结果表明，OpcCA参与了 S中时间分离的还原剂生成途径。并在激活葡萄糖-6-磷酸脱氢酶功能之外发挥作用。预计与 fbp 和 zwf 共转录的 opcA 基因具有自己的2类启动子，而 fbp 启动子被确定为1类。因此， opcA 表达可能是由于两个启动子在几乎相反的昼夜节律阶段具有活性而组成的。

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