Ditty Jayna L, Canales Shannon R, Anderson Breanne E, Williams Stanly B, Golden Susan S
Department of Biology, The University of St Thomas, St Paul, MN 55105, USA.
Department of Biology, Texas A&M University, 3258 TAMU, College Station, TX 77843-3258, USA.
Microbiology (Reading). 2005 Aug;151(Pt 8):2605-2613. doi: 10.1099/mic.0.28030-0.
The kaiA, kaiB and kaiC genes encode the core components of the cyanobacterial circadian clock in Synechococcus elongatus PCC 7942. Rhythmic expression patterns of kaiA and of the kaiBC operon normally peak in synchrony. In some mutants the relative timing of peaks (phase relationship) between these transcription units is altered, but circadian rhythms persist robustly. In this study, the importance of the transcriptional timing of kai genes was examined. Expressing either kaiA or kaiBC from a heterologous promoter whose peak expression occurs 12 h out of phase from the norm, and thus 12 h out of phase from the other kai locus, did not affect the time required for one cycle (period) or phase of the circadian rhythm, as measured by bioluminescence reporters. Furthermore, the data confirm that specific cis elements within the promoters of the kai genes are not necessary to sustain clock function.
kaiA、kaiB和kaiC基因编码了聚球藻属PCC 7942蓝细菌生物钟的核心组件。kaiA和kaiBC操纵子的节律性表达模式通常会同步达到峰值。在一些突变体中，这些转录单元之间峰值的相对时间（相位关系）发生了改变，但昼夜节律仍能强劲持续。在本研究中，研究了kai基因转录时间的重要性。通过生物发光报告基因测量发现，从一个异源启动子表达kaiA或kaiBC，该启动子的峰值表达与正常情况相差12小时，因此与另一个kai基因座相差12小时，这并不影响昼夜节律一个周期（周期时长）或相位所需的时间。此外，数据证实kai基因启动子内的特定顺式元件对于维持生物钟功能并非必需。
