A comparative analysis of nonhost resistance across the two Triticeae crop species wheat and barley

Abstract

BackgroundNonhost resistance (NHR) protects plants against a vast number of non-adapted pathogens which implicates a potential exploitation as source for novel disease resistance strategies. Aiming at a fundamental understanding of NHR a global analysis of transcriptome reprogramming in the economically important Triticeae cereals wheat and barley, comparing host and nonhost interactions in three major fungal pathosystems responsible for powdery mildew (Blumeria graminis ff. ssp.), cereal blast (Magnaporthe sp.) and leaf rust (Puccinia sp.) diseases, was performed.ResultsIn each pathosystem a significant transcriptome reprogramming by adapted- or non-adapted pathogen isolates was observed, with considerable overlap between Blumeria, Magnaporthe and Puccinia. Small subsets of these general pathogen-regulated genes were identified as differentially regulated between host and corresponding nonhost interactions, indicating a fine-tuning of the general pathogen response during the course of co-evolution. Additionally, the host- or nonhost-related responses were rather specific for each pair of adapted and non-adapted isolates, indicating that the nonhost resistance-related responses were to a great extent pathosystem-specific. This pathosystem-specific reprogramming may reflect different resistance mechanisms operating against non-adapted pathogens with different lifestyles, or equally, different co-option of the hosts by the adapted isolates to create an optimal environment for infection. To compare the transcriptional reprogramming between wheat and barley, putative orthologues were identified. Within the wheat and barley general pathogen-regulated genes, temporal expression profiles of orthologues looked similar, indicating conserved general responses in Triticeae against fungal attack. However, the comparison of orthologues differentially expressed between host and nonhost interactions revealed fewer commonalities between wheat and barley, but rather suggested different host or nonhost responses in the two cereal species.ConclusionsTaken together, our results suggest independent co-evolutionary forces acting on host pathosystems mirrored by barley- or wheat-specific nonhost responses. As a result of evolutionary processes, at least for the pathosystems investigated, NHR appears to rely on rather specific plant responses.Electronic supplementary materialThe online version of this article (10.1186/s12870-017-1178-0) contains supplementary material, which is available to authorized users.

Wheat <em>mlo</em> Mutants Show Allele-Specific Levels of Enhanced Susceptibility to the Hemibiotrophic Fungal Pathogen <em>Magnaporthe oryzae</em> pv. <em>Triticum</em>

“…The Magnaporthe isolates BR32 (Faivre-Rampant et al, 2008) and Br116.5 (Tanaka et al, 2009) were kindly provided by Didier Tharreau (CIRAD Montpellier, France) and by Yukio Tosa (Kobe University, Japan), respectively. Inoculations of wheat plants with these isolates were performed as described previously (Strugala et al, 2015;Delventhal et al, 2017). In brief, fungal cultures were maintained on oatmeal agar (20 g l −1 agar, 2 g l −1 yeast extract, 10 g l −1 starch, 30 g l −1 oat flakes) at 23 °C in the dark.…”

Arabidopsis thaliana Immunity-Related Compounds Modulate Disease Susceptibility in Barley

“…hordei (Bgh) Swiss field isolate CH4.8 was obtained from Dr. Patrick Schweizer (Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, Gatersleben, Germany). Bgh propagation and inoculation was performed essentially as described in [66]. In short, a pot containing 12 10-day-old seedlings was infected with Bgh one week prior to each experiment.…”

“…Six hours prior to the start of an experiment, these plants were shaken in order to remove old conidia and provide a uniform inoculum for the experiment [67]. Compound-or mock-treated plants were subsequently inoculated with spores from the prepared Bgh-infected plants in an inoculation tower [66] at an inoculation density of~30 spores/mm 2 . The inoculated plants were placed back in the climate chamber for 6 days.…”

Nonhost wild lettuce as a donor for resistance to downy mildew in cultivated lettuce

“…Other approaches to study the genetics of NHR include gene-expression studies (Delventhal et al 2017) and mutagenesis approaches. For instance, knock-out screenings have been used to identify nonhost genes that are necessary for the retention of resistance Zhao et al 2016).…”

“…RIS: relative infection severity level compared to susceptible control L. sativa cv Olof. A high level of specificity of nonhost responses has been found both for different pathosystems of wheat and barley, based on gene expression studies (Delventhal et al 2017). Likely, the genes for NHR against downy mildew in L. saligna are specific for lettucedowny mildew, but their applicability to other pathosystems remains to be investigated.…”