Fowler Sarah, Thomashow Michael F
Department of Energy Plant Research Laboratory and Department of Crop and Soil Sciences, Michigan State University, East Lansing, MI 48824-1312, USA.
Plant Cell. 2002 Aug;14(8):1675-90. doi: 10.1105/tpc.003483.
Many plants, including Arabidopsis, increase in freezing tolerance in response to low, nonfreezing temperatures, a phenomenon known as cold acclimation. Previous studies established that cold acclimation involves rapid expression of the CBF transcriptional activators (also known as DREB1 proteins) in response to low temperature followed by induction of the CBF regulon (CBF-targeted genes), which contributes to an increase in freezing tolerance. Here, we present the results of transcriptome-profiling experiments indicating the existence of multiple low-temperature regulatory pathways in addition to the CBF cold response pathway. The transcript levels of approximately 8000 genes were determined at multiple times after plants were transferred from warm to cold temperature and in warm-grown plants that constitutively expressed CBF1, CBF2, or CBF3. A total of 306 genes were identified as being cold responsive, with transcripts for 218 genes increasing and those for 88 genes decreasing threefold or more at one or more time points during the 7-day experiment. These results indicate that extensive downregulation of gene expression occurs during cold acclimation. Of the cold-responsive genes, 48 encode known or putative transcription factors. Two of these, RAP2.1 and RAP2.6, were activated by CBF expression and thus presumably control subregulons of the CBF regulon. Transcriptome comparisons indicated that only 12% of the cold-responsive genes are certain members of the CBF regulon. Moreover, at least 28% of the cold-responsive genes were not regulated by the CBF transcription factors, including 15 encoding known or putative transcription factors, indicating that these cold-responsive genes are members of different low-temperature regulons. Significantly, CBF expression at warm temperatures repressed the expression of eight genes that also were downregulated by low temperature, indicating that in addition to gene induction, gene repression is likely to play an integral role in cold acclimation.
许多植物，包括拟南芥，会在暴露于低温但不结冰的环境时增强其抗冻能力，这一现象被称为低温驯化。先前的研究表明，低温驯化涉及CBF转录激活因子（也称为DREB1蛋白）在低温响应下的快速表达，随后诱导CBF调控子（CBF靶向基因），从而有助于提高抗冻能力。在这里，我们展示了转录组分析实验的结果，表明除了CBF冷响应途径外，还存在多个低温调控途径。在植物从温暖环境转移到寒冷环境后的多个时间点，以及在组成型表达CBF1、CBF2或CBF3的温暖环境中生长的植物中，测定了大约8000个基因的转录水平。总共鉴定出306个基因对寒冷有响应，在为期7天的实验中，218个基因的转录本增加，88个基因的转录本在一个或多个时间点减少了三倍或更多。这些结果表明，在低温驯化过程中发生了广泛的基因表达下调。在对寒冷有响应的基因中，48个编码已知或推定的转录因子。其中两个，RAP2.1和RAP2.6，被CBF表达激活，因此可能控制CBF调控子的子调控子。转录组比较表明，只有12%的对寒冷有响应的基因是CBF调控子的特定成员。此外，至少28%的对寒冷有响应的基因不受CBF转录因子的调控，包括15个编码已知或推定转录因子的基因，这表明这些对寒冷有响应的基因是不同低温调控子的成员。值得注意的是，在温暖温度下CBF的表达抑制了八个也被低温下调的基因的表达，这表明除了基因诱导外，基因抑制可能在低温驯化中也起着不可或缺的作用。
