Abscisic Acid Induces CBF Gene Transcription and Subsequent Induction of Cold-Regulated Genes via the CRT Promoter Element

Abstract

Many cold-regulated genes of Arabidopsis are inducible by abscisic acid (ABA) as well as by cold. This has been thought to occur via two separate signaling pathways, with ABA acting via ABA-responsive promoter elements and low temperature activating the C-repeat element (CRT; dehydration-responsive) promoter element via CBF (DREB1) transcription factors. We show here that ABA is also capable of activating the CRT promoter element. Although the more recently discovered ABAinducible CBF4 transcription factor might have accounted for this, we show here that CBF1-3 transcript levels also increase in response to elevated ABA levels. This increase in CBF1-3 transcript levels appears to be at least in part due to increased activity of the CBF promoters in response to ABA. A total of 125 bp of the CBF2 promoter, which has previously been shown to be sufficient for cold-, mechanical-, and cycloheximide-induced expression, was also sufficient for ABA-induced expression. However, the ABA-responsive promoter element-like motif within this region is not needed for ABA-induced expression. An observed increase in CBF protein levels after ABA treatment, together with previous data showing that increased CBF levels are sufficient for cold-regulated gene induction, suggests that ABA-induced increases in CBF1-3 transcript levels do have the potential to activate the CRT. Our data indicate therefore that activation of the CRT may also occur via a novel ABA-inducible signaling pathway using the normally cold-inducible CBFs.The phytohormone abscisic acid (ABA) is involved in mediating responses to a number of environmental stresses including drought (Leung and Giraudat, 1998). Cellular ABA accumulates in response to such stresses, and increases in its concentration can lead to a number of physiological adaptations, including stomatal closure and growth inhibition, as well as up-regulation of specific genes. Many of the genes that are inducible by ABA are also expressed in response to cold and/or drought conditions; for example, the Arabidopsis cold-regulated (COR) genes RAB18, LTI78, and KIN2 (Kurkela and Franck, 1990; Lång and Palva, 1992;Nordin et al., 1993;Mäntylä et al., 1995). Several signaling pathways leading to COR gene expression have been described, including both ABA-dependent and ABA-independent pathways (Shinozaki and Yamaguchi-Shinozaki, 2000). The gene LTI78 (also known as COR78 or RD29A) has been studied as a paradigm system for a gene whose expression can be controlled by osmotic stress, low temperature, and ABA (Yamaguchi-Shinozaki and Shinozaki, 1994; Ishitani et al., 1997; Liu et al., 1998) via either ABAdependent or ABA-independent routes .Two cis-acting elements have been identified in the promoter of LTI78 and other COR genes that control expression under different stress conditions. The dehydration-responsive (DRE) element (YamaguchiShinozaki and Shinozaki, 1994) has been shown to mediate both cold-and osmotic stress-inducible ABA-independent gene expression (Liu et al., 1998;Shinozaki and Yamaguchi-Shinozak...

Arabidopsis AHP2, AHP3, and AHP5 histidine phosphotransfer proteins function as redundant negative regulators of drought stress response

“…In an attempt to explain this phenomenon at a molecular level, we performed a comparative microarray analysis of ahp2,3,5 and WT plants under both well-watered and drought stress conditions to identify the downstream genes of CK signaling that function in drought response. Many ABA-and/or stress-responsive genes, such as DREB1A, DREB1B, AtMYC2, and NF-YA10 (Dataset S2B), whose overexpression enhanced drought tolerance (24,25,30,31), were upregulated in either well-watered or drought-stressed ahp2,3,5 relative to WT. These data indicate that both ABA-dependent and ABA-independent pathways cross-talk with the CK pathway to regulate drought response.…”

Advances in physiological and molecular aspects of plant cold tolerance

“…Several ABA-induced genes such as Arabidopsis coldregulated (COR) genes, RAB18, LTI78 and KIN2, are up-regulated under the effect of various abiotic stresses such as cold, salt and drought (Knight et al 2004). However, although Shinozaki and Yamaguchi-Shinozaki (2000) described several signaling pathways including both ABA-dependent and ABA-independent pathways resulting in COR gene (coldresponsive genes) expression up-regulation, Thomashow (1999) and Shinozaki and Yamaguchi-Shinozaki (2000) reported cold effects on the induction of gene expression was mainly through an ABA-independent pathway.…”

TaCHP: A Wheat Zinc Finger Protein Gene Down-Regulated by Abscisic Acid and Salinity Stress Plays a Positive Role in Stress Tolerance

“…6A). A complex regulatory network controls the accumulation of DREB gene products (Gilmour et al, 1998;Zarka et al, 2003;Knight et al, 2004;Fowler et al, 2005). In Arabidopsis, ICE1 and MYB15 bind directly to the CBF promoter region (Zhu et al, 2007), and ICE1 interacts physically with MYB15.…”