A Role for the GCC-Box in Jasmonate-Mediated Activation of the PDF1.2 Gene of Arabidopsis

Abstract

The PDF1.2 gene of Arabidopsis encoding a plant defensin is commonly used as a marker for characterization of the jasmonate-dependent defense responses. Here, using PDF1.2 promoter-deletion lines linked to the ␤-glucoronidase-reporter gene, we examined putative promoter elements associated with jasmonate-responsive expression of this gene. Using stably transformed plants, we first characterized the extended promoter region that positively regulates basal expression from the PDF1.2 promoter. Second, using promoter deletion constructs including one from which the GCC-box region was deleted, we observed a substantially lower response to jasmonate than lines carrying this motif. In addition, point mutations introduced into the core GCC-box sequence substantially reduced jasmonate responsiveness, whereas addition of a 20-nucleotide-long promoter element carrying the core GCC-box and flanking nucleotides provided jasmonate responsiveness to a 35S minimal promoter. Taken together, these results indicated that the GCC-box plays a key role in conferring jasmonate responsiveness to the PDF1.2 promoter. However, deletion or specific mutations introduced into the core GCC-box did not completely abolish the jasmonate responsiveness of the promoter, suggesting that the other promoter elements lying downstream from the GCC-box region may also contribute to jasmonate responsiveness. In other experiments, we identified a jasmonate-and pathogen-responsive ethylene response factor transcription factor, AtERF2, which when overexpressed in transgenic Arabidopsis plants activated transcription from the PDF1.2, Thi2.1, and PR4 (basic chitinase) genes, all of which contain a GCC-box sequence in their promoters. Our results suggest that in addition to their roles in regulating ethylene-mediated gene expression, ethylene response factors also appear to play important roles in regulating jasmonate-responsive gene expression, possibly via interaction with the GCC-box.Diseases caused by fungal, bacterial, and viral pathogens result in enormous reductions in yield and quality from agricultural crops around the world. However, although plants are continuously challenged by pathogenic microorganisms, the development of disease is a relatively rare event. It is clear, therefore, that plants possess efficient defense systems. Effective induction of the defense response requires pathogen recognition followed by a network of signal transduction processes, resulting in the rapid activation of defense gene expression. A number of secondary signal molecules such as salicylic acid (SA), jasmonic acid (JA) and its methyl ester, methyl jasmonate (MeJA), and ethylene act to amplify and regulate defense responses after initial activation (Dong, 1998; Reymond and Farmer, 1998; Schenk et al., 2000). Interestingly, the SA-and jasmonate/ethylene-dependent signaling pathways appear to modulate plant defense responses against different classes of pathogens (for review, see Thomma et al., 2001). Treatment with MeJA provides Arabidopsis plants with protection ag...

Ethylene Response Factors in Jasmonate Signaling and Defense Response

“…In the case of AtERF2, its role as a positive regulator of MeJA response was confirmed, as had previously been suggested in plants overexpressing AtERF2 (Brown et al, 2003). Additionally, a reduction in disease symptoms relative to wild type after inoculation with F. oxysporum was observed, supporting a role for AtERF2 as a positive regulator of disease resistance.…”

The B-3 Ethylene Response Factor MtERF1-1 Mediates Resistance to a Subset of Root Pathogens inMedicago truncatulawithout Adversely Affecting Symbiosis with Rhizobia

“…The activation of defense responses by ethylene has previously been associated with the activity of transcription factors binding the GCC box in defense promoters, resulting in the induction of antimicrobial genes such as PDF1.2 and chitinases in Arabidopsis (Ohme-Takagi and Fujimoto et al, 2000;Brown et al, 2003). When transgenic hairy roots containing the 43GCC::luciferase construct were challenged with R. solani, an early induction of the reporter gene suggested that an ethylene-mediated response was induced at the initial stages of infection, while an additional induction peaking at 14 h suggested a secondary phase of activity of the GCC element.…”

Involvement of Abscisic Acid in the Coordinated Regulation of a Stress-Inducible Hexose Transporter (VvHT5) and a Cell Wall Invertase in Grapevine in Response to Biotrophic Fungal Infection

“…Two kilobases of sequence upstream of the predicted start codon of each of the VvHT1 to -5 and VvcwINV genes was obtained from the published grapevine PN40024 genome sequence (Jaillon et al, 2007) and analyzed for putative regulatory motifs associated with stress-induced transcription using the PLACE database (Higo et al, 1999). A number of motifs were identified: GCC box (Brown et al, 2003), MYC recognition (Abe et al, 1997), T/G box (Boter et al, 2004), wound response element (Palm et al, 1990), and abscisic acid response elements (ABREs; Choi et al, 2000;Hattori et al, 2002). Figure 3 also shows the presence of Suc-responsive motifs (SURE1, Suc box 3) shown previously by Cakir et al (2003) to be involved in the transcriptional regulation of VvHT1.…”

“…The presence of regulatory motifs associated with stress-induced transcription in a 2-kb promoter region from the published grapevine PN40024 genome sequence is shown. Recognition sequences are as follows: GCC box (GCCGCC; Brown et al, 2003), T/G box (AACGTG; Boter et al, 2004), MYC (CACATG; Abe et al, 1997), ABRE (ACGTGG/TC; Hattori et al, 2002), and wound response element (WRE; AAA/TGTATCC/GA; Palm et al, 1990). Also shown are the Suc-responsive motifs SURE (ATA-GAAA) and Suc box 3 (AAATCA----AA), identified by Cakir et al (2003) to be involved in the transcriptional regulation of VvHT1.…”