Department of Postharvest Science of Fresh Produce, Agricultural Research Organization, The Volcani Center, P.O. Box 6, 50250, Bet Dagan, Israel.
Plant Mol Biol. 2010 Apr;72(6):659-71. doi: 10.1007/s11103-010-9605-8. Epub 2010 Feb 2.
The transcription factor CCA1 (CIRCADIAN CLOCK ASSOCIATED 1) participates in both light and circadian clock regulation in Arabidopsis. Two sets of transgenic plants in which GFP was fused to the CCA1 promoter with (1.3-kb fragment) or without (1.01-kb fragment) its 5'UTR were engineered. The transgenic plants transformed with the promoter including the 5'UTR had altered circadian regulation resulting in elongated hypocotyls, a bushy appearance and delayed flowering. In contrast, the transgenic plants transformed with the promoter without the 5'UTR showed earlier flowering than the wild type. Changes in CCA1, LHY and TOC1 gene expression were investigated under light-dark (L:D) fluctuations, continuous darkness (D:D) and continuous light (L:L). The circadian expression of CCA1 was altered in both sets of transgenic plants, being repressed in the plants transformed with the 1.01-kb fragment and constitutively overexpressed in those transformed with the 1.3-kb fragment. Under L:D conditions, regulation of LHY and TOC1 expression was separated from CCA1 regulation in both sets of transgenic plants, with intact rhythmic expression of both LHY and TOC1. Under D:D conditions, the rhythmic expression of LHY and TOC1 was lost in the 1.3 plants but retained with some erratic pattern under L:L conditions. In the 1.01 plants, under both D:D and L:L conditions the rhythmic expression was retained. These results indicate separate light-induced signal-transmission pathways for LHY and CCA1.
转录因子 CCA1（circadian clock associated 1）参与拟南芥的光和生物钟调节。构建了两套将 GFP 融合到 CCA1 启动子的转基因植物，其中一套启动子包含其 5'UTR（1.3-kb 片段），另一套不包含（1.01-kb 片段）。转化包含 5'UTR 的启动子的转基因植物表现出改变的生物钟调节，导致下胚轴伸长、植株茂密和开花延迟。相比之下，转化不包含 5'UTR 的启动子的转基因植物比野生型更早开花。在光暗（L:D）波动、连续黑暗（D:D）和连续光照（L:L）下，研究了 CCA1、LHY 和 TOC1 基因表达的变化。两套转基因植物的 CCA1 昼夜表达均发生改变，转化 1.01-kb 片段的植物中被抑制，转化 1.3-kb 片段的植物中持续过表达。在 L:D 条件下，两套转基因植物中 LHY 和 TOC1 的表达调控与 CCA1 分开，LHY 和 TOC1 都具有完整的节律表达。在 D:D 条件下，转化 1.3-kb 片段的植物中 LHY 和 TOC1 的节律表达丧失，但在 L:L 条件下仍保留一些不规则的模式。在转化 1.01-kb 片段的植物中，在 D:D 和 L:L 条件下均保留了节律表达。这些结果表明 LHY 和 CCA1 有独立的光诱导信号转导途径。
