Salicylic acid and the plant pathogen Erwinia carotovora induce defense genes via antagonistic pathways

Abstract

SummaryInfection of tobacco plants with the plant pathogenic bacterium Erwinia carotovora subsp, carotovora or treatment of plants with Erwinia-derived elicitor preparations leads to the induction of a number of genes thought to play a role in plant defense response to pathogens. In order to determine the role of salicylic acid (SA) in the induction of the Erwinia responsive genes, the accumulation of mRNAs for these and other genes encoding pathogenesis-related proteins (PR genes) in response to both Erwinia elicitors and SA was determined. PR genes were identified which were preferentially induced by Erwinia elicitor preparations, one gene was induced by SA but not by Erwinia, and another gene was induced by both type of treatments. The differential expression of these genes and the timing of induction suggest that SA is not the signal molecule leading to the early response of plants to Erwinia. This was demonstrated by experiments using transgenic NahG plants that overproduce a salicylate hydroxylase inactivating SA. The elicitation of PR genes by Erwinia was similar in NahG and wild-type plants. Therefore, induction of plant defense genes by Erwinia and SA seems to be by two distinct pathways leading to expression of separate sets of genes. Furthermore, we could demonstrate that Erwinia elicitors antagonize the SA-mediated induction of PR genes. Similarly, SA appeared to inhibit the induction of PR genes elicited by Erwinia. The observed antagonism between the two signal transduction pathways indicates the presence of a common regulatory element in both pathways that acts downstream of SA in the SA-mediated response.

Salicylic acid can reduce infection symptoms caused by Dickeya solani in tissue culture grown potato (Solanum tuberosum L.) plants

“…It is the first case dealing with SA treatment used in in vitro potato plants against infection caused by D. solani and also, the first description of a simple screening system combining in vitro (potato) plants, the fluorescently-labelled pathogenic bacteria and (fluorescent) macroscopy, that can be used on large number of (potato) plants and with different chemicals tested as prospective elicitors in vitro. Elicitation of potato plants against pectinolytic bacteria has been analyzed previously in several studies (Palva et al 1994;Vidal et al 1997;Luzzatto et al 2007b). For example, Palva et al (1994) showed that the SA treatment together with application of P. carotovorum subsp.…”

“…carotovorum on tobacco resulted in hypersensitivity reaction and induction of yetunknown factors able to neutralize the plant cell wall degrading enzymes produced by the pathogen. Vidal et al (1997) demonstrated that compounds from P. carotovorum subsp. carotovorum may act antagonistically with SA elicitation.…”

Isolation of an extracellular protease gene of Erwinia carotovora subsp. carotovora strain SCC3193 by transposon mutagenesis and the role of protease in phytopathogenicity

“…involves a fine balance between avoiding the induction of plant defence mechanisms and the rapid killing of plant cells by pectolytic enzymes. Vidal et al (1997) showed the rapid local induction of pathogenesis-related (PR) genes during the early stages of infection (4-8 h after infection). Suppression of these resistance mechanisms is important during the initial stages of infection when the synthesis of virulence factors is not sufficient for the establishment of infection.…”

Signaling in Plant Resistance Responses: Divergence and Cross-Talk of Defense Pathways

“…Another example comes from studies on the interaction between the bacterial pathogen E. carotovora and its host plants tobacco and Arabidopsis. Infection of leaves of these plants with E. carotovora, or treatment of the leaves with elicitors of this pathogen, activated an SA-independent systemic resistance and a set of defense-related genes that differs from that induced upon exogenous application of SA (Vidal et al, 1997;Norman-Setterblad et al, 2000). Interestingly, most of the E. carotovora-induced genes appeared to be regulated by JA and ET.…”