CBF2/DREB1C is a negative regulator ofCBF1/DREB1BandCBF3/DREB1Aexpression and plays a central role in stress tolerance inArabidopsis

Abstract

CBF͞DREB1 (C-repeat-binding factor͞dehydration responsive element-binding factor 1) genes encode a small family of transcriptional activators that have been described as playing an important role in freezing tolerance and cold acclimation in Arabidopsis. To specify this role, we used a reverse genetic approach and identified a mutant, cbf2, in which the CBF2͞DREB1C gene was disrupted. Here, we show that cbf2 plants have higher capacity to tolerate freezing than WT ones before and after cold acclimation and are more tolerant to dehydration and salt stress. All these phenotypes correlate with a stronger and more sustained expression of CBF͞DREB1-regulated genes, which results from an increased expression of CBF1͞DREB1B and CBF3͞DREB1A in the mutant. In addition, we show that the expression of CBF1͞DREB1B and CBF3͞DREB1A in response to low temperature precedes that of CBF2͞DREB1C. These results indicate that CBF2͞DREB1C negatively regulates CBF1͞DREB1B and CBF3͞ DREB1A, ensuring that their expression is transient and tightly controlled, which, in turn, guarantees the proper induction of downstream genes and the accurate development of Arabidopsis tolerance to freezing and related stresses.F reezing temperatures greatly limit the geographical distribution and growing season of plants and cause negative effects on crop quality and productivity. As a consequence, appreciable effort has been conducted to determine the adaptive mechanisms plants have evolved to survive this adverse environmental condition. Many plants, including Arabidopsis, increase their freezing tolerance in response to low, nonfreezing temperatures. This process, called cold acclimation (1), is complex and involves a number of biochemical and physiological changes, ranging from alterations in lipid composition to accumulation of sugars (2). Different studies have suggested that low-temperature-regulated gene expression is critical in plants for cold acclimation (2). Low-temperature-responsive genes encode a diverse number of proteins, including enzymes involved in respiration and metabolism of carbohydrates, lipids, phenylpropanoids and antioxidants, molecular chaperones, antifreeze proteins, among others, with a believed function in freezing tolerance (2).During the past few years, substantial progress has been made toward understanding how low temperatures regulate gene expression. In particular, a family of transcription factors in Arabidopsis known either as C-repeat-binding factor (CBF)1, CBF2, and CBF3 (3, 4) or dehydration-responsive elementbinding factor (DREB)1B, DREB1C, and DREB1A (5), respectively, has been identified. These factors belong to the Apetala 2͞ethylene-responsive element-binding protein (AP2͞ EREBP) family of DNA-binding proteins (6) and bind to the cold-and dehydration-responsive DNA regulatory element (DRE) (7), also termed C-repeat (CRT) (8). CRT͞DRE elements contain the conserved CCGAC core sequence, which is sufficient to induce gene transcription under cold stress (7,8) and is present in the promoters of many cold-induc...

ArabidopsisCBF1 and CBF3 have a different function than CBF2 in cold acclimation and define different gene classes in the CBF regulon

“…In a previous work (15), we reported that the expression of CBF1 and CBF3 during cold acclimation precedes that of CBF2, reinforcing the idea that the CBF proteins may have different functional activities. Furthermore, we isolated an Arabidopsis null mutant, cbf2, in which the CBF2 gene was disrupted by a T-DNA insertion (15).…”

“…Furthermore, we isolated an Arabidopsis null mutant, cbf2, in which the CBF2 gene was disrupted by a T-DNA insertion (15). Unexpectedly, cbf2 plants were not impaired in their capacity to cold acclimate but, on the contrary, they showed increased freezing tolerance before and after cold acclimation, as well as increased tolerance to dehydration and salt stress.…”

Functionality of soybean CBF/DREB1 transcription factors

“…However in Arabidopsis, AtCBF genes are strongly and transiently up-regulated; peaking at 2-4 h following cold treatments and returning to much lower levels by 24 h [40]. To determine whether cold-induced increases in the GmCBFDREB1 genes were transient, we examined transcript levels of GmDREB1A;1 and GmDREB1A;2 and a representative of another known cold-inducible transcription factor SCOF-1 (Glyma17g35430) [29] during early cold stress.…”

The OsMYB30 Transcription Factor Suppresses Cold Tolerance by Interacting with a JAZ Protein and Suppressing β-Amylase Expression

“…According to previous studies, CBF/DREBs are important components in the cold stress response in which CBF1/DREB1B and CBF3/DREB1A are positive regulators, while CBF2/DREB1C is a negative regulator (Novillo et al, 2004). There have been quite a few studies on MYB transcription factors whose functions either depend on the CBF/DREB pathway, such as MYB15 (Agarwal et al, 2006;Miura et al, 2007), MYB96 (Lee and Seo, 2015), and MYBS3 (Su et al, 2010), or do not depend on the CBF/DREB pathway, such as OsMYB3R-2 (Ma et al, 2009) and OsMYB4 (Laura et al, 2010).…”