The Arabidopsis CBF Gene Family Is Composed of Three Genes Encoding AP2 Domain-Containing Proteins Whose Expression Is Regulated by Low Temperature but Not by Abscisic Acid or Dehydration1

Abstract

We have identified two genes from Arabidopsis that show high similarity with CBF1, a gene encoding an AP2 domain-containing transcriptional activator that binds to the low-temperatureresponsive element CCGAC and induces the expression of some cold-regulated genes, increasing plant freezing tolerance. These two genes, which we have named CBF2 and CBF3, also encode proteins containing AP2 DNA-binding motifs. Furthermore, like CBF1, CBF2 and CBF3 proteins also include putative nuclear-localization signals and potential acidic activation domains. The CBF2 and CBF3 genes are linked to CBF1, constituting a cluster on the bottom arm of chromosome IV. The high level of similarity among the three CBF genes, their tandem organization, and the fact that they have the same transcriptional orientation all suggest a common origin. CBF1, CBF2, and CBF3 show identical expression patterns, being induced very rapidly by low-temperature treatment. However, in contrast to most of the cold-induced plant genes characterized, they are not responsive to abscisic acid or dehydration. Taken together, all of these data suggest that CBF2 and CBF3 may function as transcriptional activators, controlling the level of low-temperature gene expression and promoting freezing tolerance through an abscisic acid-independent pathway.

Functionality of soybean CBF/DREB1 transcription factors

“…Following strong accumulation in initial response to cold, both GmDREB1A;1 and GmDREB1A;2 were significantly decreased by 48 h. These rapid, large and transient accumulations in response to cold stress are very similar to the transient expression pattern of Arabidopsis CBF genes [13]. While the level of the SCOF-1 transcript was also strongly increased in response to cold stress, the transient change ( Figure 2) was much less than that observed in the DREB1A transcripts.…”

“…All of these genes have very similar Nuclear Localization Signals (NLS) and AP2 domains followed by an acidic region at C-terminus. Unlike CBF1, 2 and 3 of Arabidopsis and tomato [13,28], the soybean CBF genes are not found as tandem arrays on the same chromosome (Chromosome 4 in Arabidopsis, Chromosome 3 in tomato), but rather were scattered among seven different soybean chromosomes. Soybean is a tetraploid plant, with about 75% of the genes having multiple copies [39].…”

“…CBF genes are members of the DREB (dehydration responsive element binding protein) family transcription factors that contain AP2 DNA-binding domains. AtCBF1, AtCBF2, and AtCBF3 (DREB1B, DREB1C, and DREB1A; respectively) are up regulated significantly and rapidly by cold stress specifically, but much less so by ABA or dehydration [12,13]. In contrast, AtCBF4 (DREB1D) and AtDREB2 genes are more specifically regulated by ABA, salinity, and dehydration but not by cold stress [12,14,15].…”

“…Both the DREB1 and DREB2 family of proteins have binding activity with elements containing the core nucleotide sequence CCGAC [12,13,16]. Genes up-regulated by constitutive expression of AtCBF3 (DREB1A) contain ACCGAC significantly more 4 frequently than GCCGAC and TGTCGG in their promoters; while ACCGAC, CCGACT and GTCGGT are present in similar frequency in promoters of genes upregulated by AtDREB2A [17,18].…”

Cloning and characterization of cold, salt and drought inducible C-repeat binding factor gene from a highly cold adapted ecotype of Lepidium latifolium L.

“…The LlCBF gene was observed to induce strongly within 30 min of exposure to drought, salinity and low temperature stress and therefore said to be early responsive to multiple stresses . Medina et al (1999) also reported that CBF genes showed high expression in response to low temperature stress treatment and the transcript was detectable as early as 30 min of exposure to 4°C, and reached to maximum expression level at 1 h after the exposure. Our result also corroborate to those described earlier in LpCBF3 from rye grass, Ptcbfb from Poncirus trifoliata, OsAP211 from rice, VviDREB1 from Vaccinium vitis-idaea, MbDREB1 from apple, but confront with those observed in DREB1 from aloe, BrCBF from chinese cabbage, OsDREB1B under cold stress (Wang and He 2007;Wang et al 2009;Qin et al 2007;Gao et al 2009;Wang et al 2010b;Yang et al 2011;Jiang et al 2011).…”