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  • 1
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    Online Resource
    Subfamily-Specific Specialization of RGH1/MLA Immune Receptors in Wild Barley
    Scientific Societies ; 2019
    In:  Molecular Plant-Microbe Interactions® Vol. 32, No. 1 ( 2019-01), p. 107-119
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 32, No. 1 ( 2019-01), p. 107-119
    Abstract: The barley disease resistance (R) gene locus mildew locus A (Mla) provides isolate-specific resistance against the powdery mildew fungus Blumeria graminis hordei and has been introgressed into modern cultivars from diverse germplasms, including the wild relative Hordeum spontaneum. Known Mla disease resistance specificities to B. graminis hordei appear to encode allelic variants of the R gene homolog 1 (RGH1) family of nucleotide-binding domain and leucine-rich repeat (NLR) proteins. Here, we sequenced and assembled the transcriptomes of 50 H. spontaneum accessions representing nine populations distributed throughout the Fertile Crescent. The assembled Mla transcripts exhibited rich sequence diversity, linked neither to geographic origin nor population structure, and could be grouped into two similar-sized subfamilies based on two major N-terminal coiled-coil (CC) signaling domains that are both capable of eliciting cell death. The presence of positively selected sites located mainly in the C-terminal leucine-rich repeats of both MLA subfamilies, together with the fact that both CC signaling domains mediate cell death, implies that the two subfamilies are actively maintained in the population. Unexpectedly, known MLA receptor variants that confer B. graminis hordei resistance belong exclusively to one subfamily. Thus, signaling domain divergence, potentially as adaptation to distinct pathogen populations, is an evolutionary signature of functional diversification of an immune receptor. [Formula: see text] Copyright © 2018 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI-07-18-0186-FI
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2019
    detail.hit.zdb_id: 2037108-1
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  • 2
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    The Role of G Protein Alpha Subunits in the Infection Process of the Gray Mold Fungus Botrytis cinerea
    Scientific Societies ; 2001
    In:  Molecular Plant-Microbe Interactions® Vol. 14, No. 11 ( 2001-11), p. 1293-1302
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 14, No. 11 ( 2001-11), p. 1293-1302
    Abstract: To identify signal transduction pathways of the gray mold fungus Botrytis cinerea involved in host infection, we used heterologous hybridization and a polymerase chain reaction (PCR)-based approach to isolate two genes (bcg1 and bcg2) encoding α subunits of heterotrimeric GTP-binding proteins. Both genes have homologues in other fungi: bcg1 is a member of the Gα i class, whereas bcg2 has similarities to the magC gene of Magnaporthe grisea and the gna-2 gene of Neurospora crassa. Reverse-transcription (RT)-PCR experiments showed clearly that both genes are expressed at very early stages in infected bean leaves. Gene replacement experiments were performed for both genes. bcg1 null mutants differ in colony morphology from the wild-type strain, do not secrete extracellular proteases, and show clearly reduced pathogenicity on bean and tomato. Conidia germination and penetration of plant tissue is not disturbed in bcg1 mutants, but the infection process stops after formation of primary lesions. In contrast, bcg2 mutants show wild-type colony morphology in axenic culture and are only slightly reduced in pathogenicity. Complementation of bcg1 mutants with the wild-type gene copy led to the full recovery of colony morphology, protease secretion, and pathogenicity on both host plants. Application of exogenous cyclic AMP restored the wild-type growth pattern of bcg1 mutants, but not the protease secretion, implicating an essential role of BCG1 in different signaling pathways.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI.2001.14.11.1293
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2001
    detail.hit.zdb_id: 2037108-1
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  • 3
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    Online Resource
    Diversity at the Mla Powdery Mildew Resistance Locus from Cultivated Barley Reveals Sites of Positive Selection
    Scientific Societies ; 2010
    In:  Molecular Plant-Microbe Interactions® Vol. 23, No. 4 ( 2010-04), p. 497-509
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 23, No. 4 ( 2010-04), p. 497-509
    Abstract: The Mla locus in barley (Hordeum vulgare) conditions isolate-specific immunity to the powdery mildew fungus (Blumeria graminis f. sp. hordei) and encodes intracellular coiled-coil (CC) domain, nucleotide-binding (NB) site, and leucine-rich repeat (LRR)-containing receptor proteins. Over the last decades, genetic studies in breeding material have identified a large number of functional resistance genes at the Mla locus. To study the structural and functional diversity of this locus at the molecular level, we isolated 23 candidate MLA cDNAs from barley accessions that were previously shown by genetic studies to harbor different Mla resistance specificities. Resistance activity was detected for 13 candidate MLA cDNAs in a transient gene-expression assay. Sequence alignment of the deduced MLA proteins improved secondary structure predictions, revealing four additional, previously overlooked LRR. Analysis of nucleotide diversity of the candidate and validated MLA cDNAs revealed 34 sites of positive selection. Recombination or gene conversion events were frequent in the first half of the gene but positive selection was also found when this region was excluded. The positively selected sites are all, except two, located in the LRR domain and cluster in predicted solvent-exposed residues of the repeats 7 to 15 and adjacent turns on the concave side of the predicted solenoid protein structure. This domain-restricted pattern of positively selected sites, together with the length conservation of individual LRR, suggests direct binding of effectors to MLA receptors.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI-23-4-0497
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2010
    detail.hit.zdb_id: 2037108-1
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  • 4
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    Barley Rom1 Reveals a Potential Link Between Race-Specific and Nonhost Resistance Responses to Powdery Mildew Fungi
    Scientific Societies ; 2005
    In:  Molecular Plant-Microbe Interactions® Vol. 18, No. 4 ( 2005-04), p. 291-299
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 18, No. 4 ( 2005-04), p. 291-299
    Abstract: The Rar1 gene, identified in the context of race-specific powdery mildew resistance mediated by the Hordeum vulgare (barley) resistance (R) gene Mla12, is required for the function of many R-mediated responses in monoand dicotyledonous plant species. Mla resistance is associated with an oxidative burst and a subsequent cell death reaction of attacked cells. Rar1 mutants are impaired in these responses and, to identify genetic elements which negatively regulate the Mla12-triggered response, we have screened mutagenized Mla12 rar1 mutant populations for restoration of the resistance response. Here we describe the restoration of Mla12-specified resistance (rom1) mutant that restores features of disease resistance to a Blumeria graminis f. sp. hordei isolate expressing the avirulence gene AvrMla12 and retains susceptibility to an isolate lacking AvrMla12. Histochemical analyses show that, in rom1 mutant plants, a whole-cell oxidative burst and cell death response in attacked epidermal cells is restored in the incompatible interaction. Defense responses against tested inappropriate powdery mildews, B. graminis f. sp. tritici and Golovinomyces orontii, were diminished in rar1 mutant plants and enhanced in rom1 mutant plants relative to the wild type. These findings indicate antagonistic activities of Rar1 and Rom1 and reveal their contribution to nonhost and race-specific resistance responses.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI-18-0291
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2005
    detail.hit.zdb_id: 2037108-1
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  • 5
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    Nonhost Resistance in Arabidopsis-Colletotrichum Interactions Acts at the Cell Periphery and Requires Actin Filament Function
    Scientific Societies ; 2006
    In:  Molecular Plant-Microbe Interactions® Vol. 19, No. 3 ( 2006-03), p. 270-279
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 19, No. 3 ( 2006-03), p. 270-279
    Abstract: Pathogenesis of nonadapted fungal pathogens is often terminated coincident with their attempted penetration into epidermal cells of nonhost plants. The genus Colletotrichum represents an economically important group of fungal plant pathogens that are amenable to molecular genetic analysis. Here, we investigated interactions between Arabidopsis and Colletotrichum to gain insights in plant and pathogen processes activating nonhost resistance responses. Three tested nonadapted Colletotrichum species differentiated melanized appressoria on Arabidopsis leaves but failed to form intracellular hyphae. Plant cells responded to Colletotrichum invasion attempts by the formation of PMR4/GSL5-dependent papillary callose. Appressorium differentiation and melanization were insufficient to trigger this localized plant cell response, but analysis of nonpathogenic C. lagenarium mutants implicates penetration-peg formation as the inductive cue. We show that Arabidopsis PEN1 syntaxin controls timely accumulation of papillary callose but is functionally dispensable for effective preinvasion (penetration) resistance in nonhost interactions. Consistent with this observation, green fluorescent protein-tagged PEN1 did not accumulate at sites of attempted penetration by either adapted or nonadapted Colletotrichum species, in contrast to the pronounced focal accumulations of PEN1 associated with entry of powdery mildews. We observed extensive reorganization of actin microfilaments leading to polar orientation of large actin bundles towards appressorial contact sites in interactions with the nonadapted Colletotrichum species. Pharmacological inhibition of actin filament function indicates a functional contribution of the actin cytoskeleton for both preinvasion resistance and papillary callose formation. Interestingly, the incidence of papilla formation at entry sites was greatly reduced in interactions with C. higginsianum isolates, indicating that this adapted pathogen may suppress preinvasion resistance at the cell periphery.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI-19-0270
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2006
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  • 6
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    Functional Conservation of Wheat and Rice Mlo Orthologs in Defense Modulation to the Powdery Mildew Fungus
    Scientific Societies ; 2002
    In:  Molecular Plant-Microbe Interactions® Vol. 15, No. 10 ( 2002-10), p. 1069-1077
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 15, No. 10 ( 2002-10), p. 1069-1077
    Abstract: Homologs of barley Mlo are found in syntenic positions in all three genomes of hexaploid bread wheat, Triticum aestivum, and in rice, Oryza sativa. Candidate wheat orthologs, designated TaMlo-A1, TaMlo-B1, and TaMlo-D1, encode three distinct but highly related proteins that are 88% identical to barley MLO and appear to originate from the three diploid ancestral genomes of wheat. TaMlo-B1 and the rice ortholog, OsMlo2, are able to complement powdery mildew-resistant barley mlo mutants at the single-cell level. Overexpression of TaMlo-B1 or barley Mlo leads to super-susceptibility to the appropriate powdery mildew formae speciales in both wild-type barley and wheat. Surprisingly, overexpression of either Mlo or TaMlo-B1 also mediates enhanced fungal development to tested inappropriate formae speciales. These results underline a regulatory role for MLO and its wheat and rice orthologs in a basal defense mechanism that can interfere with forma specialis resistance to powdery mildews.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI.2002.15.10.1069
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2002
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  • 7
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    A Network of Phosphate Starvation and Immune-Related Signaling and Metabolic Pathways Controls the Interaction between Arabidopsis thaliana and the Beneficial Fungus Colletotrichum tofieldiae
    Scientific Societies ; 2021
    In:  Molecular Plant-Microbe Interactions® Vol. 34, No. 5 ( 2021-05), p. 560-570
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 34, No. 5 ( 2021-05), p. 560-570
    Abstract: The beneficial root-colonizing fungus Colletotrichum tofieldiae mediates plant growth promotion (PGP) upon phosphate (Pi) starvation in Arabidopsis thaliana. This activity is dependent on the Trp metabolism of the host, including indole glucosinolate (IG) hydrolysis. Here, we show that C. tofieldiae resolves several Pi starvation-induced molecular processes in the host, one of which is the downregulation of auxin signaling in germ-free plants, which is restored in the presence of the fungus. Using CRISPR/Cas9 genome editing, we generated an Arabidopsis triple mutant lacking three homologous nitrilases (NIT1 to NIT3) that are thought to link IG-hydrolysis products with auxin biosynthesis. Retained C. tofieldiae-induced PGP in nit1/2/3 mutant plants demonstrated that this metabolic connection is dispensable for the beneficial activity of the fungus. This suggests that either there is an alternative metabolic link between IG-hydrolysis products and auxin biosynthesis, or C. tofieldiae restores auxin signaling independently of IG metabolism. We show that C. tofieldiae, similar to pathogenic microorganisms, triggers Arabidopsis immune pathways that rely on IG metabolism as well as salicylic acid and ethylene signaling. Analysis of IG-deficient myb mutants revealed that these metabolites are, indeed, important for control of in planta C. tofieldiae growth: however, enhanced C. tofieldiae biomass does not necessarily negatively correlate with PGP. We show that Pi deficiency enables more efficient colonization of Arabidopsis by C. tofieldiae, possibly due to the MYC2-mediated repression of ethylene signaling and changes in the constitutive IG composition in roots. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 Inte rnational license .
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI-08-20-0233-R
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2021
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  • 8
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    Functional Analysis of the Cytochrome P450 Monooxygenase Gene bcbot1 of Botrytis cinerea Indicates That Botrydial Is a Strain-Specific Virulence Factor
    Scientific Societies ; 2005
    In:  Molecular Plant-Microbe Interactions® Vol. 18, No. 6 ( 2005-06), p. 602-612
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 18, No. 6 ( 2005-06), p. 602-612
    Abstract: The micrographic phytopathogen Botrytis cinerea causes gray mold diseases in a large number of dicotyledonous crop plants and ornamentals. Colonization of host tissue is accompanied by rapid killing of plant cells ahead of the growing hyphen, probably caused by secretion of nonspecific phytotoxins, e.g., the sesquiterpene botrydial. Although all pathogenic strains tested so far had been shown to secrete botrydial and although the toxin causes comparable necrotic lesions as infection by the fungus, the role of botrydial in the infection process has not been elucidated so far. Here, we describe the functional characterization of bcbot1, encoding a P450 monooxygenase and provide evidence that it is involved in the botrydial pathway, i.e., it represents the first botrydial biosynthetic gene identified. We show that bcbot1 is expressed in planta and that expression in vitro and in planta is controlled by an α-subunit of a heterotrimeric GTP-binding protein, BCG1. Deletion of bcbot1 in three standard strains of B. cinerea shows that the effect on virulence (on several host plants) is strain-dependent; only deletion in one of the strains (T4) led to reduced virulence.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI-18-0602
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2005
    detail.hit.zdb_id: 2037108-1
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  • 9
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    Online Resource
    Root-Associated Bacterial and Fungal Community Profiles of Arabidopsis thaliana Are Robust Across Contrasting Soil P Levels
    Scientific Societies ; 2018
    In:  Phytobiomes Journal Vol. 2, No. 1 ( 2018-01), p. 24-34
    Details
    In: Phytobiomes Journal, Scientific Societies, Vol. 2, No. 1 ( 2018-01), p. 24-34
    Abstract: Plant survival depends on the ability of roots to sense and acquire nutrients in soils, which harbor a rich diversity of microbes. A subset of this microcosm interacts with plant roots and collectively forms root-associated microbial communities, termed the root microbiota. Under phosphorus-limiting conditions, some plants can engage in mutualistic interactions, for example with arbuscular mycorrhizal fungi. Here, we describe how Arabidopsis thaliana, which lacks the genetic capacity for establishing the aforementioned symbiosis, interacts with soil-resident bacteria and fungi in soil from a long-term phosphorus fertilization trial. Long-term, contrasting fertilization regimes resulted in an ∼6-fold and ∼2.4-fold disparity in bioavailable and total phosphorous, respectively, which may explain differences in biomass of A. thaliana plants. Sequencing of marker genes enabled us to characterize bacterial and fungal communities present in the bulk soil, rhizosphere, and root compartments. Phosphorus had little effect on alpha- or beta-diversity indices, but more strongly influences bacterial and fungal community shifts in plant-associated compartments compared with bulk soil. The significant impact of soil P abundance could only be resolved at operational taxonomic unit level, and these subtle differences are more pronounced in the root compartment. We conclude that despite decades of different fertilization, both bacterial and fungal soil communities remained unexpectedly stable in soils tested, suggesting that the soil biota is resilient over time to nutrient supplementation. Conversely, low-abundance, root-associated microbes, which collectively represent 2 to 3% of the relative abundance of bacteria and fungi in the roots, exhibited a subtle, yet significant shift between the two soils. [Formula: see text] Copyright © 2018 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
    Type of Medium: Online Resource
    ISSN: 2471-2906 , 2471-2906
    URL: Article
    DOI: 10.1094/PBIOMES-09-17-0042-R
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2018
    detail.hit.zdb_id: 2897163-2
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  • 10
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    Tissue Dependence and Differential Cordycepin Sensitivity of Race-Specific Resistance Responses in the Barley—Powdery Mildew Interaction
    Scientific Societies ; 1997
    In:  Molecular Plant-Microbe Interactions® Vol. 10, No. 7 ( 1997-09), p. 830-839
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 10, No. 7 ( 1997-09), p. 830-839
    Abstract: Epidermal cell monolayers prepared from partially dissected barley (Hordeum vulgare) coleoptiles were used for in vivo analysis of race-specific resistance to powdery mildew (Erysiphe graminis f. sp. hordei) specified by host genes Mla-1, Mla-12, and Mlg. Complete resistance governed by each of these genes is closely associated with hypersensitive cell death (hypersensitive response, HR) in primary leaf tissue. In contrast, Mla-12 coleoptile tissue reveals a fully compatible, Mla-1 coleoptile tissue a partially compatible, and Mlg coleoptile tissue an incompatible interaction upon challenge with pathogen races carrying corresponding avirulence functions. Quantitative recording of single plant-fungus interaction sites showed arrest of fungal development in papillae on Mlg coleoptiles. On Mla-1 and Mla-12 coleoptiles, attacked cells become predominantly penetrated by the fungus. Approximately one third of penetrated cells on Mla-1 coleoptiles subsequently undergo an HR. These sites reveal no further fungal development. Both Mlg and Mla-12 coleoptiles fail to mount an HR. The effect of cordycepin (3′-deoxyadenosine), an inhibitor of mRNA synthesis, was studied in planta on primary leaf tissue of Mla-12 and Mlg genotypes. Host cell death triggered by either gene is reduced to background levels observed in the near-isogenic compatible interaction and exhibits the same dose-dependent cordycepin sensitivity. Inhibition of Mlg-triggered, single-cell HR is not accompanied by release of fungal growth arrest, indicating cordycepin insensitivity of a papillae-associated resistance component. The data suggest that host cell death is a requisite component for expression of Mla-type but not Mlg-type resistance.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI.1997.10.7.830
    Language: English
    Publisher: Scientific Societies
    Publication Date: 1997
    detail.hit.zdb_id: 2037108-1
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