Fowler Sarah G, Cook Daniel, Thomashow Michael F
Michigan State University-U.S. Department of Energy Plant Research Laboratory , Michigan State University, East Lansing, Michigan 48824, USA.
Plant Physiol. 2005 Mar;137(3):961-8. doi: 10.1104/pp.104.058354. Epub 2005 Feb 22.
Exposing Arabidopsis (Arabidopsis thaliana) plants to low temperature results in rapid induction of CBF1, 2, and 3 (CBF1-3; also known as DREB1B, C, and A, respectively), which encode transcriptional activators that induce expression of a battery of genes that increase plant freezing and chilling tolerance. Recently, it has been shown that basal levels of CBF3 transcripts and those of certain CBF-regulated genes exhibit circadian cycling. Here, we further explored the regulation of CBF1-3 by the circadian clock. The results indicated that the extent to which CBF1-3 transcripts accumulated in response to low temperature was dependent on the time of day that the plants were exposed to low temperature and that this was regulated by the circadian clock. The highest and lowest levels of cold-induced CBF1-3 transcript accumulation occurred at 4 and 16 h after subjective dawn, respectively. An analysis of CBF2 promoter-reporter gene fusions indicated that this control included transcriptional regulation. In addition, the cold responsiveness of RAV1 and ZAT12, genes that are cold induced in parallel with CBF1-3, was also subject to circadian regulation. However, whereas the maximum level of cold-induced RAV1 transcript accumulation occurred at the same time of day as did CBF1-3 transcripts, that of ZAT12 was in reverse phase, i.e. the highest level of cold-induced ZAT12 transcript accumulation occurred 16 h after subjective dawn. These results indicate that cold-induced expression of CBF1-3, RAV1, and ZAT12 is gated by the circadian clock and suggest that this regulation likely occurs through at least two nonidentical (though potentially overlapping) signaling pathways.
将拟南芥植株暴露于低温下会迅速诱导CBF1、2和3（分别为CBF1-3；也称为DREB1B、C和A）的表达，它们编码转录激活因子，可诱导一系列增加植物抗冻性和抗冷性的基因表达。最近的研究表明，CBF3转录本的基础水平以及某些受CBF调控的基因的转录本呈现昼夜节律循环。在此，我们进一步探究了生物钟对CBF1-3的调控。结果表明，CBF1-3转录本响应低温积累的程度取决于植株暴露于低温的时间，且这是由生物钟调控的。冷诱导的CBF1-3转录本积累的最高和最低水平分别出现在主观黎明后的4小时和16小时。对CBF2启动子-报告基因融合体的分析表明，这种调控包括转录调控。此外，与CBF1-3同时受冷诱导的RAV1和ZAT12基因的冷响应性也受昼夜节律调控。然而，虽然冷诱导的RAV1转录本积累的最高水平与CBF1-3转录本在同一天的同一时间出现，但ZAT12的情况则相反，即冷诱导的ZAT12转录本积累的最高水平出现在主观黎明后的16小时。这些结果表明，CBF1-3、RAV1和ZAT12的冷诱导表达受生物钟的门控，并表明这种调控可能至少通过两条不同（尽管可能重叠）的信号通路发生。
