CBF:平衡植物低温应答与生长发育的关键

低温是影响植物生长发育以及植被分布的重要环境因子。目前,低温信号研究中比较清楚的是CBF依赖的低温信号途径。该文总结了近年来有关CBF的研究成果,详细介绍了CBF家族成员在植物耐寒性中的重要作用,着重分析与讨论CBF介导的低温调控网络及一系列复杂调控机制。理解CBF的复杂作用机制有助于了解植物中CBF介导的冷信号如何平衡耐寒性与生长发育,进而有助于耐寒作物的培育。     

Expression of a sweet cherry DREB1/CBF ortholog in Arabidopsis confers salt and freezing tolerance

Dehydration responsive element binding protein 1 (DREB1)/C-repeat binding factor (CBF) induces the expression of many stress-inducible genes in Arabidopsis. We have previously reported the identification of three DREB1/ICBF homologs from sweet cherry (Prunus avium). To identify the function of these homologs, one of the genes, CIG-B, was transformed into Arabidopsis. In one of the transgenic plant lines, the DREB1/CBF target gene cor15a was induced in the absence of stress treatment. The cor15a-overexpressing transgenic plant exhibited mild growth retardation and had greater salt and freezing tolerance than did the wild-type and the transgenic lines in which cor15a was not induced. These results suggest that this sweet cherry DREB1/CBF homolog has a function similar to that of DREB1/CBF.     

& 转录因子CBF在植物抗寒中的重要作用

低温能够诱导植物许多基因的表达,从而使植物具有抗寒性,这种现象称为冷驯化。对于植物冷驯化的分子机理,目前研究的最多的是CBF转录因子调控的信号转导途径,其作用途径可归纳为：CBF(C-repeat Binding Factor)转录因子→CRT/DRE(C-repeat /Dehydration Responsive Element)基序→COR基因表达→植物抗寒性增加。研究CBF转录因子在抗寒中的作用机制,能为提高植物的抗寒性,培育抗寒作物品种提供新方向。      

The role of CBF transcriptional activators in two Citrus species (Poncirus and Citrus) with contrasting levels of freezing tolerance

Citrus species are considered cold sensitive, yet Poncirus trifoliata , an interfertile Citrus relative, is extremely cold tolerant and can survive freezes at −20°C when fully cold acclimated. To better understand the molecular basis of this difference in freezing tolerance, C-repeat-binding factors (CBFs) from P. trifoliata and Citrus paradisi (grapefruit) were isolated and characterized. Based on our results, P. trifoliata and C. paradisi do contain a CBF pathway for cold-regulated gene expression, and similar to other species, they both appear to contain small CBF families. The nucleotide and amino acid sequences of PtCBF1 and CpCBF1 are highly homologous. However, differences in cold-induced expression were observed. PtCBF1 accumulates both earlier and to higher levels than CpCBF1 . Furthermore, CORc115 , a cold-induced group II LEA gene, also accumulates earlier and to higher levels in P. trifoliata in response to cold temperatures. The regulatory region of CORc115 contains a putative C-repeat/dehydration-responsive element that is specifically recognized and bound by PtCBF, indicating that CORc115 is a target of PtCBF1. This study provides the first evidence of a correlation between CBF expression (timing and quantity) and the degree of cold tolerance in two closely related species with wide differences in cold tolerance. The importance of using Poncirus and Citrus , two non-model organisms, to address new questions about the CBF pathway is illustrated, as these results provide novel evidence that the CBF expression pattern may play an important role in the notable difference in cold tolerance between these two related species.