Novillo Fernando, Medina Joaquín, Salinas Julio
Departamento de Biotecnología, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Carretera de la Coruña, Km. 7, 28040 Madrid, Spain.
Proc Natl Acad Sci U S A. 2007 Dec 26;104(52):21002-7. doi: 10.1073/pnas.0705639105. Epub 2007 Dec 19.
The C-repeat-binding factor (CBF)/dehydration-responsive element-binding factor (DREB1) proteins constitute a small family of Arabidopsis transcriptional activators (CBF1/DREB1B, CBF2/DREB1C, and CBF3/DREB1A) that play a prominent role in cold acclimation. A fundamental question about these factors that remains to be answered is whether they are functionally equivalent. Recently, we reported that CBF2 negatively regulates CBF1 and CBF3 expression, and that CBFs are subjected to different temporal regulation during cold acclimation, which suggested this might not be the case. In this study, we have analyzed the expression of CBF genes in different tissues of Arabidopsis, during development and in response to low temperature, and characterized RNA interference (RNAi) and antisense lines that fail to accumulate CBF1 or/and CBF3 mRNAs under cold conditions. We found that CBF1 and CBF3 are regulated in a different way than CBF2. Moreover, in contrast to CBF2, CBF1 and CBF3 are not involved in regulating other CBF genes and positively regulate cold acclimation by activating the same subset of CBF-target genes. All these results demonstrate that CBF1 and CBF3 have different functions than CBF2. We also found that the CBF regulon is composed of at least two different kind of genes, one of them requiring the simultaneous expression of both CBF1 and CBF3 to be properly induced. This indicates that CBF1 and CBF3 have a concerted additive effect to induce the whole CBF regulon and the complete development of cold acclimation.
C-重复结合因子（CBF）/脱水响应元件结合因子（DREB1）蛋白构成了拟南芥转录激活因子的一个小家族（CBF1/DREB1B、CBF2/DREB1C和CBF3/DREB1A），它们在低温驯化中发挥着重要作用。关于这些因子仍有待回答的一个基本问题是它们在功能上是否等效。最近，我们报道CBF2负调控CBF1和CBF3的表达，并且在低温驯化过程中CBF受到不同的时间调控，这表明情况可能并非如此。在本研究中，我们分析了拟南芥不同组织中、发育过程中以及对低温响应时CBF基因的表达，并对在低温条件下无法积累CBF1或/和CBF3 mRNA的RNA干扰（RNAi）和反义株系进行了表征。我们发现CBF1和CBF3的调控方式与CBF2不同。此外，与CBF2不同，CBF1和CBF3不参与调控其他CBF基因，而是通过激活相同的CBF靶基因子集来正向调控低温驯化。所有这些结果表明，CBF1和CBF3与CBF2具有不同的功能。我们还发现CBF调控子由至少两种不同类型的基因组成，其中一种需要同时表达CBF1和CBF3才能被正确诱导。这表明CBF1和CBF3具有协同加性效应，以诱导整个CBF调控子并使低温驯化完全发展。
