Background Plants respond to abiotic stress through complex regulation of transcription, including both transcriptional activation and repression. of the protein. Expression of RAP2.1 is strongly induced by drought and cold stress via an ABA-independent pathway. Arabidopsis plants overexpressing RAP2.1 show enhanced sensitivity to chilly and drought stresses, while rap2.1-1 and rap2.1-2 T-DNA insertion alleles result in Rabbit Polyclonal to RAB3IP reduced sensitivity to these stresses. The reduced stress sensitivity of the herb made up of the rap2.1 allele can be genetically complemented by the expression of RAP2.1, but not by the expression of EAR-motif-mutated RAP2.1. Furthermore, chromatin immunoprecipitation (ChIP) analysis has recognized Responsive to desiccation/Cold-regulated (RD/COR) genes as downstream targets of RAP2.1 in vivo. Stress-induced expression of the RD/COR genes is usually repressed by overexpression of RAP2.1 and is increased in plants expressing the rap2.1 allele. In addition, RAP2.1 can negatively regulate its own expression by binding to DREs present in its own promoter. Our DAMPA data suggest that RAP2.1 acts as a negative transcriptional regulator in defence responses to chilly and drought stress in Arabidopsis. DAMPA Conclusions A hypothetical model for the role of RAP2.1 in modulating herb responses to chilly and drought is proposed in this study. It appears that RAP2.1 acts as a negative “subregulon” of DREB-type activators and is involved in the precise regulation of expression of stress-related genes, acting to keep stress responses under tight control. Background Drought, chilly and high salinity are the major adverse environmental factors that can adversely impact herb growth and crop production. A variety of genes are induced under these stress conditions, enabling plants to adapt to these abiotic stresses [1]. It is well known that complex transcriptional regulatory networks are involved in stress-induced changes in gene expression [1]. Among the best characterized stress-responsive transcription factors are the dehydration responsive element (DRE) binding proteins DREBs [2-4]. The DREB protein family can be divided into six small groups (A-1~A-6) based on similarity in the APETALA2 (AP2) DNA-binding domain name [5]. Most reports have focused on DREB-type transcriptional activators. Three DREB1 proteins, DREB1A, DREB1B, and DREB1C, users of the A-1 DREB group, transactivate cold-induced expression of RD/COR/LTI (responsive to dehydration/cold-responsive/low-temperature-induced) genes through interactions between their AP2 DNA binding domains and the core DRE cis-elements (A/GCCGAC) present in the promoters of the target genes [2,4,6]. Overexpression of each DREB1 constitutively induces the DREB1 regulon and enhances herb freezing tolerance [7,8]. Similar results have been reported for the constitutive active form of the DREB2 proteins, the A-2 group users, under dehydration and high salinity stress conditions [3,9]. TINY, a member of the A-4 DREB group, can activate the expression of both DRE- and ERE- (for ethylene responsive element) regulated genes. In this way, TINY plays a role in the crosstalk between abiotic and biotic stress-responsive gene expression pathways by connecting the DRE- and ERE-mediated signaling pathways [10]. RAP2.4, a member of the A-6 group, functions as a transactivator of DRE- and ERE-mediated genes that are responsive to light, ethylene and drought, suggesting that RAP2.4 functions in the cross-talk between the light and ethylene signaling pathways to coordinately regulate multiple development processes and stress responses [11]. Although the mechanisms of activation mediated by DREB proteins involved in herb stress responses are relatively well studied, little is known concerning the unfavorable regulation of stress genes mediated by the DREB-type transcriptional repressors. Transcriptional repression is an essential mechanism in the precise control of gene expression [12]. Transcriptional repressors may maintain the stress response genes in an off state in the absence of any stress. In addition, they may keep the expression of stress response genes under tight control, to prevent the metabolic waste and self-inflicted damage that can be caused by a runaway stress response [13]. In plants, transcriptional repressors made up of the ERF-associated amphiphilic repression (EAR) motif have been reported to play important functions in modulating herb stress and defense responses [13]. The EAR-motif [L/FDLNL/F(x)P] was first identified in the C-terminal region of class II ERFs (Ethylene Response Factor) and C2H2- (Cys2/His2) type zinc-finger proteins [14]. Recently, many studies have revealed the in planta functions of EAR-motif-containing repressors in modulating herb responses to drought [15-17], chilly [16-18], UV [19], pathogen contamination [20], and hormone signaling [15,21,22]. The EAR-repressor AtERF4 binds to the GCC box of PDF1.2, a gene encoding an antimicrobial peptide, and represses its jasmonate-ethylene-dependent expression. Overexpression of AtERF4 in Arabidopsis renders the plants more susceptible to the wilt pathogen Fusarium oxysporum [20]. Similar to AtERF4, AtERF7 binds to the GCC box of ABA-induced genes and represses their transcription. Arabidopsis plants overexpressing AtERF7 show DAMPA a reduced sensitivity of guard cells to ABA.