Tomato defense to the powdery mildew fungus: differences in expression of genes in susceptible, monogenic- and polygenic resistance responses are mainly in timing

Abstract

Oidium neolycopersici is a causal agent of tomato powdery mildew. In this paper, gene expression profiles were investigated of susceptible, monogenicand polygenic resistant tomato genotypes in response to O. neolycopersici infection by using cDNA-AFLP. Around 30,000 TDFs (Transcript Derived Fragments), representing~22% of the transcriptome based on in silico estimation, were identified and 887 TDFs were differentially expressed (DE-TDFs) upon inoculation with O. neolycopersici spores. Forty-two percent of the identified DE-TDFs were detected in both the compatible and incompatible interactions, a subset of these were studied for their temporal patterns. All of these common induced DE-TDFs displayed an expression peak at 7 days post incoluation in monogenic resistant response but sustained up-regulation in the susceptible and the polygenic resistant response. While more than half of these common DE-TDFs showed earlier timing in incompatible interactions compared to compatible interaction. Only 2% of the identified DE-TDFs were specific to either the monogenic or the polygenic resistant response. By annotation of the 230 sequenced DE-TDFs we found that 34% of the corresponding transcripts were known to be involved in plant defense, whereas the other transcripts played general roles in signal transduction (11%), regulation (24%), protein synthesis and degradation (11%), energy metabolism (12%) including photosynthesis, photorespiration and respiration.

Genetics and molecular mechanisms of resistance to powdery mildews in tomato (Solanum lycopersicum) and its wild relatives

“…2). The narrower range of differentially expressed genes in NILOl-1 suggested that compared to NIL-ol-2 and NIL-Ol-4 the response of NIL-Ol-1 upon PM attack is more similar to MM, which is in agreement with the results obtained from cDNA-AFLP analysis (Li et al 2006(Li et al , 2007.…”

“…This similarity is likely due to the fact that slow HR is involved in the resistance mediated by Ol-1 and Ol-qtls, resulting in a similar pattern of fungal growth in MM and NILs carrying Ol-1 and Ol-qtls (Li et al 2007(Li et al , 2012. Most of these sequenced inducible transcripts showed homology to genes with functions in defence responses, implying that Ol-1-and Ol-qtls-mediated responses likely employ overlapping components of defence pathways occurring in basal immunity, however the timing and magnitude of responses may determine the interaction outcome (Li et al 2006(Li et al , 2012. Though the resistance mediated by ol-2 is associated with papilla formation, distinct from HR, more than 50 % of the DETDFs that were induced in NIL-Ol-1 also showed upregulation in NIL-ol-2 (Li et al 2007).…”

“…In order to compare the resistance mechanism mediated by monogenic Ol genes and Ol-qtls, we studied the transcript profiles by cDNA-AFLP (Li et al 2006(Li et al , 2007 and microarray analysis (unpublished data).…”

“…cDNA-AFLP profiling clarified that the majority of the up-regulated differentially expressed-transcript derived fragments (DE-TDFs) are common in MM, NIL-Ol-1 and NIL-Ol-qtls, with differences in timing of expression for certain DE-TDFs (Li et al 2006(Li et al , 2007(Li et al , 2012. This similarity is likely due to the fact that slow HR is involved in the resistance mediated by Ol-1 and Ol-qtls, resulting in a similar pattern of fungal growth in MM and NILs carrying Ol-1 and Ol-qtls (Li et al 2007(Li et al , 2012.…”

“…Given the important role of SA in HR induction (Vlot et al 2009;Love et al 2008), the early induction in SA pathway in NIL-Ol-4 is expected. Interestingly, SA is required for the Mi-1-mediated resistance to potato aphids, but not to nematodes (Li et al 2006;Mantelin et al 2013). …”