Overexpression of the ArabidopsisCBF3Transcriptional Activator Mimics Multiple Biochemical Changes Associated with Cold Acclimation

Abstract

We further investigated the role of the Arabidopsis CBF regulatory genes in cold acclimation, the process whereby certain plants increase in freezing tolerance upon exposure to low temperature. The CBF genes, which are rapidly induced in response to low temperature, encode transcriptional activators that control the expression of genes containing the C-repeat/ dehydration responsive element DNA regulatory element in their promoters. Constitutive expression of either CBF1 or CBF3 (also known as DREB1b and DREB1a, respectively) in transgenic Arabidopsis plants has been shown to induce the expression of target COR (cold-regulated) genes and to enhance freezing tolerance in nonacclimated plants. Here we demonstrate that overexpression of CBF3 in Arabidopsis also increases the freezing tolerance of cold-acclimated plants. Moreover, we show that it results in multiple biochemical changes associated with cold acclimation: CBF3-expressing plants had elevated levels of proline (Pro) and total soluble sugars, including sucrose, raffinose, glucose, and fructose. Plants overexpressing CBF3 also had elevated P5CS transcript levels suggesting that the increase in Pro levels resulted, at least in part, from increased expression of the key Pro biosynthetic enzyme ⌬ 1 -pyrroline-5-carboxylate synthase. These results lead us to propose that CBF3 integrates the activation of multiple components of the cold acclimation response.

Functionality of soybean CBF/DREB1 transcription factors

“…Typically, overexpression of AtCBF1-3 increases the expression of AtRD29a and AtCOR47, utilizing 4 and 3 CRT/DRE elements present within 1kb upstream of the ATG, respectively [21,41]. Arabidopsis plants overexpressing AtCBF1-3 have a dwarf phenotype due to regulation of GA biosynthesis pathway by CBF genes [22,23,51]. Exogenous GA3 application returns the normal growth habit to transgenic tomato plants expressing AtCBF1 [26].…”

“…Overexpression of AtDREB1A or AtDREB2A in Arabidopsis transgenic plants induces the expression of cold responsive genes such as RD29a and COR47 without exposure to low temperature [18][19][20]. The accumulation of downstream genes mediated by CBF/DREB1 genes, increases abiotic stress tolerances to freezing, dehydration, and high salt [14,[20][21][22][23][24]. In cold-intolerant tomato, the transgenic expression of AtCBF1 gene increased cold regulated genes [25] [ 26,27] and the expression of AtCBF1 in tomato increases freezing tolerance [26][27][28].…”

“…In Arabidopsis, the accumulation of CBF causes up-regulation of a downstream regulon [17,21,23,48,49]. In Arabidopsis the CRT/DRE is the most common element in cold inducible promoters; however, in soybean the most common element in the promoters of cold-induced genes are the ABRE and T/G box [17].…”

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 transcription factors play a paramount role in controlling various component traits of stress tolerance by regulating an array of genes. Earlier studies demonstrated that the expression of the CBF genes in Arabidopsis resulted in an increased tolerance to freezing, salt and drought stresses (Liu et al 1998;Jaglo-Ottesen et al 1998;Kasuga et al 1999;Gilmour et al 2000). The cDNAs encoding CBF transcription factors have been identified and cloned from various plant species including Arabidopsis, rice, wheat, canola, soybean (Liu et al 1998;Dubouzet et al 2003;Shen et al 2003;Li et al 2005).…”

Nitrogen fixation is synchronized with carbon metabolism inLotus japonicusandMedicago truncatulanodules under salt stress

“…It has been argued that the accumulation of sucrose under salinity, associated with inhibition of the sucrose hydrolytic enzyme sucrose synthase (Arrese-Igor et al 1999), induces a deficiency of carbon for bacteroids with the subsequent inhibition of nitrogenase activity (Hunt and Layzell 1993). A strong correlation between sugar accumulation and osmotic stress tolerance has been widely reported, including transgenic experiments (Gilmour et al 2000;Streeter et al 2001;Taji et al 2002).…”