PpERF3b, a transcriptional repressor from peach, contributes to disease susceptibility and side branching in EAR-depende
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ORIGINAL PAPER
PpERF3b, a transcriptional repressor from peach, contributes to disease susceptibility and side branching in EAR-dependent and -independent fashions S. Sherif • I. El-Sharkawy • G. Paliyath S. Jayasankar
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Received: 3 January 2013 / Revised: 18 February 2013 / Accepted: 1 March 2013 / Published online: 21 March 2013 Ó Springer-Verlag Berlin Heidelberg 2013
Abstract Key message Peach ERF3b is a potent transcriptional repressor for defense-related genes even in the presence of similar levels of transcriptional activators and can interfere with plant development through pathways independent of the EAR motif. Abstract Ethylene response factors (ERFs) are a major group of plant transcription factors with either activation or repression capabilities on gene transcription. Repressortype ERFs are characterised by an intrinsic motif, namely the ERF-associated amphiphilic repression motif (EAR). Here we report the identification of three genes from peach (Prunus persica), PpERF12, PpERF3a and PpERF3b, encoding for ERF repressors. The transcription kinetics of these genes was investigated by qRT-PCR after inoculation of peach leaves with Xanthomonas campestris pv. pruni.
Communicated by P. Kumar. A contribution to the Special Issue: Plant Hormone Signaling.
Electronic supplementary material The online version of this article (doi:10.1007/s00299-013-1405-6) contains supplementary material, which is available to authorized users. S. Sherif I. El-Sharkawy S. Jayasankar (&) Department of Plant Agriculture, University of Guelph, 4890 Victoria Av. N., PO Box 7000, Vineland Station, ON L0R 2E0, Canada e-mail: [email protected] S. Sherif G. Paliyath Department of Plant Agriculture, University of Guelph, Guelph, ON N1G 2W1, Canada S. Sherif I. El-Sharkawy Department of Horticulture, Faculty of Agriculture, Damanhour University, Damanhour, Egypt
All three genes showed higher induction in the susceptible ‘BabyGold 5’, than in the resistant ‘Venture’ peach varieties suggesting a negative role for these genes in disease resistance. The functional potency of PpERF3b has been confirmed in vivo by its ability to repress the expression of GUS-reporter gene. To better understand the functional role of PpERF3b, the full-length and the EAR-truncated (PpERF3bDEAR) genes were overexpressed in tobacco (Nicotiana tabacum). Both transgenic plants (PpERF3b and PpERF3bDEAR) uniformly exhibited precocious side branching, which suggests the interference of PpERF3b with auxin-mediated dormancy of lateral shoots. Consistent with that the expression of auxin-response factors (Nt-ARF1, Nt-ARF6 and Nt-ARF8) was significantly downregulated in transgenic plants compared to the wild type (WT). Although side branching was independent of EAR motif, the response of transgenic plants to inoculation by Pseudomonas syringae pv. tabaci was EAR dependent. Transgenic plants overexpressing PpERF3bDEAR showed less disease symptoms than those overexpressing the fulllength gene or WT plants. Resistance of PpERF3bDEAR plants was associated with
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