Partial Resistance of Tomato to Phytophthora infestans Is Not Dependent upon Ethylene, Jasmonic Acid, or Salicylic Acid Signaling Pathways

Abstract

We compared tomato defense responses to Phytophthora infestans in highly compatible and partially compatible interactions. The highly compatible phenotype was achieved with a tomato-specialized isolate of P. infestans, whereas the partially compatible phenotype was achieved with a nonspecialized isolate. As expected, there was induction of the hypersensitive response (HR) earlier during the partially compatible interaction. However, contrary to our expectation, pathogenesis-related (PR) gene expression was not stimulated sooner in the partially compatible interaction. While the level of PR gene expression was quite similar in the two interactions, the LeDES gene (which encodes an enzyme necessary for the production of divinyl ethers) was expressed at a much higher level in the partially compatible interaction at 48 h after inoculation. Host reaction to the different pathogen genotypes was not altered (compared with wild type) in mutant tomatoes that were ethylene-insensitive (Never-ripe) or those with reduced ability to accumulate jasmonic acid (def-1). Similarly, host reaction was not altered in NahG transgenic tomatoes unable to accumulate salicylic acid. These combined data indicate that partial resistance in tomato to P. infestans is independent of ethylene, jasmonic acid, and salicylic acid signaling pathways.

The Role of the Jasmonate Response in Plant Susceptibility to Diverse Pathogens with a Range of Lifestyles

“…In our experiments on P. infestans, we found results similar to Cohen. The discrepancy between Smart et al (2003) and the findings of Cohen et al (1993) and this study are difficult to resolve because none of the data is reported by Smart et al (2003). Thus, where quantitative data have been presented, jasmonate appears to be effective at reducing susceptibility of tomato to P. infestans.…”

“…In addition, Cohen et al (1993) found that induction of the jasmonate response, using methyl jasmonate, resulted in increased resistance to P. infestans, whereas Smart et al (2003) failed to find an effect of jasmonatedeficient plants on resistance to P. infestans. In our experiments on P. infestans, we found results similar to Cohen.…”

“…Like many pathogens, the six other species have a less clear-cut lifestyle. P. infestans is a hemibiotrophic oomycete, with an initial biotrophic phase (3-5 d) and a later necrotrophic stage (Smart et al, 2003). By contrast, Septoria lycopersici, while often classified as a necrotroph, has a brief biotrophic phase in tomato, as indicated by intercellular growth between living cells at the lesion margin (Bouarab et al, 2002; V.J.…”

Potato R1 resistance gene confers resistance against Phytophthora infestans in transgenic tomato plants

“…The Pr-proteins, particularly PR-1 and PR-5, are reported as important components of the defence mechanism of potato against P. infestans (Wang et al 2006). PR genes induced in this interaction have been described as "pathogen response" genes (Smart et al 2003). Indeed, van Loon et al (2006) demonstrated that, in tomato, PR-1 was able to reduce sporangia germination and germ-tube length.…”

Expression of a magainin-type antimicrobial peptide gene (MSI-99) in tomato enhances resistance to bacterial speck disease

“…Reactions of MSI-99-expressing tomato lines to Phytophthora infestans (late blight) were assessed using detached-leaflets and growth chamber and field tests as described by Legard et al (1995), Smart et al (2003), and Mayton et al (2001), respectively. The 19 lines included in the detached leaflet assays and the four lines in the growth chamber tests were the same type of plants as those used in bacterial speck and early blight tests.…”