ERF5 and ERF6 Play Redundant Roles as Positive Regulators of JA/Et-Mediated Defense against Botrytis cinerea in Arabidopsis

Abstract

The ethylene response factor (ERF) family in Arabidopsis thaliana comprises 122 members in 12 groups, yet the biological functions of the majority remain unknown. Of the group IX ERFs, the IXc subgroup has been studied the most, and includes ERF1, ERF14 and ORA59, which play roles in plant innate immunity. Here we investigate the biological functions of two members of the less studied IXb subgroup: ERF5 and ERF6. In order to identify potential targets of these transcription factors, microarray analyses were performed on plants constitutively expressing either ERF5 or ERF6. Expression of defense genes, JA/Et-responsive genes and genes containing the GCC box promoter motif were significantly upregulated in both ERF5 and ERF6 transgenic plants, suggesting that ERF5 and ERF6 may act as positive regulators of JA-mediated defense and potentially overlap in their function. Since defense against necrotrophic pathogens is generally mediated through JA/Et-signalling, resistance against the fungal necrotroph Botrytis cinerea was examined. Constitutive expression of ERF5 or ERF6 resulted in significantly increased resistance. Although no significant difference in susceptibility to B. cinerea was observed in either erf5 or erf6 mutants, the erf5 erf6 double mutant showed a significant increase in susceptibility, which was likely due to compromised JA-mediated gene expression, since JA-induced gene expression was reduced in the double mutant. Taken together these data suggest that ERF5 and ERF6 play positive but redundant roles in defense against B. cinerea. Since mutual antagonism between JA/Et and salicylic acid (SA) signalling is well known, the UV-C inducibility of an SA-inducible gene, PR-1, was examined. Reduced inducibilty in both ERF5 and ERF6 constitutive overexepressors was consistent with suppression of SA-mediated signalling, as was an increased susceptibility to avirulent Pseudomonas syringae. These data suggest that ERF5 and ERF6 may also play a role in the antagonistic crosstalk between the JA/Et and SA signalling pathways.

Quantitative Peptidomics Study Reveals That a Wound-Induced Peptide from PR-1 Regulates Immune Signaling in Tomato

“…We suggest that ERF5 is a mediator of CAPE1 defense responses because of the GCC box, a cis-acting element found in the promoter of many JA/ethylene-inducible and PR genes. ERF5 was also demonstrated to positively regulate SA signaling and plant immunities against the bacterial pathogen Pst DC3000 and improve plant resistance to pathogens by activating several PR genes (Moffat et al, 2012;Son et al, 2012). In tomato, the overexpression of ERF5 was observed to induce PR genes and conferred tolerance to Ralstonia solanacearum (Li et al, 2011).…”

Bacteria-Triggered Systemic Immunity in Barley Is Associated with WRKY and ETHYLENE RESPONSIVE FACTORs But Not with Salicylic Acid

“…AtERF4 expression is induced by ABA, JA, ET, and abiotic stress, and overexpression of AtERF4 represses ABA responses, whereas it may enhance JA responsiveness (Yang et al, 2005;Memelink, 2009). Other plant AP2-ERFs, including OsERF922 and wheat PATHOGEN-INDUCED ERF1, also appear to regulate abiotic stress tolerance or disease resistance against necrotrophic pathogens mediated by JA, ABA, or ET (Pré et al, 2008;Liu et al, 2012;Moffat et al, 2012;Maruyama et al, 2013;Zhu et al, 2014). Notably, HvERF-like and HvERF44411 were systemically induced by MeJA and/or ABA application (Fig.…”

The Hevea brasiliensis AP2/ERF superfamily: from ethylene signalling to latex harvesting and physiological disease response

“…Members of this group were characterized by a protein motif of activator-type EDLL in the C-terminal (Tiwari et al, 2012). The involvement of ERF-IX (ERF1, ORA59, ERF5, and ERF6 genes) in the ethylene and jasmonate signalling was clearly demonstrated in Arabidopsis (Cheng et al, 2013a;Moffat et al, 2012;Zarei et al, 2011). The ERF1 and ORA59 genes belong to the subgroup of ERF-IXc while ERF5 and ERF6 genes are within the subgroup of ERF-IXb.…”

“…The ERF-IX group probably contains the transcription factors whose involvement in the response to pathogens has been most extensively studied (Licausi et al, 2013a;Zarei et al, 2011;Moffat et al, 2012). Members of this group were characterized by a protein motif of activator-type EDLL in the C-terminal (Tiwari et al, 2012).…”