Stage-Specific Suppression of Basal Defense Discriminates Barley Plants Containing Fast- and Delayed-Acting Mla Powdery Mildew Resistance Alleles

Department of Plant Pathology, Center for Plant Responses to Environmental Stresses, USDA-ARS, Iowa State University, Ames, IA 50011, USA.
Molecular Plant-Microbe Interactions (Impact Factor: 3.94). 10/2006; 19(9):939-47. DOI: 10.1094/MPMI-19-0939
Source: PubMed


Nonspecific recognition of pathogen-derived general elicitors triggers the first line of plant basal defense, which in turn, preconditions the host towards resistance or susceptibility. To elucidate how basal defense responses influence the onset of Mla (mildew resistance locus a)-specified resistance, we performed a meta-analysis of GeneChip mRNA expression for 155 basal defense-related genes of barley (Hordeum vulgare) challenged with Blumeria graminis f. sp. hordei, the causal agent of powdery mildew disease. In plants containing the fast-acting Mla1, Mla6, or Mla13 alleles, transcripts hyper-accumulated from 0 to 16 h after inoculation (hai) in both compatible and incompatible interactions. Suppression of basal defense-related transcripts was observed after 16 hai only in compatible interactions, whereas these transcripts were sustained or increased in incompatible interactions. By contrast, in plants containing wild-type and mutants of the delayed-acting Mla12 allele, an early hyper-induction of transcripts from 0 to 8 hai was observed, but the expression of many of these genes is markedly suppressed from 8 to 16 hai. These results suggest that the inhibition of basal defense facilitates the development of haustoria by the pathogen, consequently delaying the onset of host resistance responses. Thus, we hypothesize that the regulation of basal defense influences host-cell accessibility to the fungal pathogen and drives allelic diversification of gene-specific resistance phenotypes.

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Available from: Roger P Wise, Jun 25, 2014
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    • "Profiling of barley superoxide dismutase 1 (HvSOD1) expression. Samples were extracted from 7-d-old seedling first leaves (PO:0007094) that were used for time course Barley1 GeneChip profiling (Caldo et al., 2006; Meng et al., 2009; Moscou et al., 2011), based on a split-split-plot design. Seedlings were inoculated with Blumeria graminis f. sp. "
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    • "). RKN are biotrophic pathogens and the success of infection depends on the ability of the pathogen to overcome PTI, as reported for other pathogens . Several type III secreted protein effectors and fungal effectors have been shown to contribute to pathogen virulence by suppressing PTI (Caldo et al. 2006; Göhre and Robatzek 2008; Kim et al. 2009 "
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    • "C. graminicola initially colonizes the plant leaf biotrophically and later switches to a necrotrophic lifestyle. It has been well established that biotrophic pathogens such as Uromyces vignae and U. maydis as well as hemibiotrophs such as M. graminicola, during the biotrophic phase, must suppress or attenuate host defenses to be able to parasitize the invaded host cells (Panstruga, 2003; Caldo et al., 2006; Jones and Dangl, 2006; Adhikari et al., 2007; Doehlemann et al., 2008; Eich- Table II "
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