The leucine-rich repeats in allelic barley MLA immune receptors define specificity towards sequence-unrelated powdery mildew avirulence effectors with a predicted common RNase-like fold

Nucleotide-binding domain leucine-rich repeat-containing receptors (NLRs) in plants can detect avirulence (AVR) effectors of pathogenic microbes. The Mildew locus a (Mla) NLR gene has been shown to confer resistance against diverse fungal pathogens in cereal crops. In barley, Mla has undergone allelic diversification in the host population and confers isolate-specific immunity against the powdery mildew-causing fungal pathogen Blumeria graminis forma specialis hordei (Bgh). We previously isolated the Bgh effectors AVRA1, AVRA7, AVRA9, AVRA13, and allelic AVRA10/AVRA22, which are recognized by matching MLA1, MLA7, MLA9, MLA13, MLA10 and MLA22, respectively. Here, we extend our knowledge of the Bgh effector repertoire by isolating the AVRA6 effector, which belongs to the family of catalytically inactive RNase-Like Proteins expressed in Haustoria (RALPHs). Using structural prediction, we also identified RNase-like folds in AVRA1, AVRA7, AVRA10/AVRA22, and AVRA13, suggesting that allelic MLA recognition specificities could detect structurally related avirulence effectors. To better understand the mechanism underlying the recognition of effectors by MLAs, we deployed chimeric MLA1 and MLA6, as well as chimeric MLA10 and MLA22 receptors in plant co-expression assays, which showed that the recognition specificity for AVRA1 and AVRA6 as well as allelic AVRA10 and AVRA22 is largely determined by the receptors’ C-terminal leucine-rich repeats (LRRs). The design of avirulence effector hybrids allowed us to identify four specific AVRA10 and five specific AVRA22 aa residues that are necessary to confer MLA10- and MLA22-specific recognition, respectively. This suggests that the MLA LRR mediates isolate-specific recognition of structurally related AVRA effectors. Thus, functional diversification of multi-allelic MLA receptors may be driven by a common structural effector scaffold, which could be facilitated by proliferation of the RALPH effector family in the pathogen genome.

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RESISTANCE TO MILDEW OF SELECTION FAMILY OF RED CURRANT THE BELAYA POTAPENKO × № 1426-21-80

Vestnik of the Russian agricultural science ◽

10.30850/vrsn/2020/4/38-40 ◽

1970 ◽

pp. 38-40

Author(s):

O. O. Kalinina ◽

O. D. Golyaeva ◽

O. V. Panfilova ◽

А. V. Pikunova

Keyword(s):

Powdery Mildew ◽

Field Resistance ◽

Disease Development ◽

Artificial Infection ◽

Sources Of Resistance ◽

Climate Conditions ◽

High Productivity ◽

Local Soil ◽

The Family ◽

Red Currant

Powdery mildew is one of the most harmful fungal diseases that causes economically significant damage to berry plantations. The disease is common in all areas of currant cultivation in the Russian Federation. In this regard, in modern conditions of intensive berry growing, the problem of breeding cultivars that are highly resistant to diseases and pests becomes urgent. Breeders have a difficult task to combine the adaptive potential of the cultivar with its annual high productivity and resistance to biotic environmental factors. When studying the adaptability of introduced cultivars of red currant and selected forms of the Institute to local soil and climate conditions, the following cultivars were identified as sources of economic and useful characteristics and involved in selection: ‘Belaya Potapenko’ as a complex source of resistance powdery mildew and high marketable and taste qualities of berries; SS 1426-21-80 as a source of high productivity and long racemes (raceme length 11-13 cm; up to 20 berries in the raceme). On their base the selection family of red currant has been developed: Belaya Potapenko × ♂SS 1426-21-80. The study of data on the destruction of hybrid seedlings of the selection family by powdery mildew showed that in epiphytotic conditions, the percentage of intensity of the disease development varies over the periods of screening from 0.2% in May to 20.4% in June. Such indicators served as a prerequisite for conducting a comparative test of breeding material in the field under artificial infection with powdery mildew. After artificial infection on the background of epiphytosis, the rate of intensity of the disease development increased slightly and amounted to 35.6% for the family. There were 30 highly resistant seedlings in the family, 10 of which have remained stable and highly resistant since 2018. In these plants we can assume the presence of the so-called field resistance, controlled by polygens, each of which does not give a visible effect of stability, but with different combinations determines one or another of its degree. Highly resistant seedlings will be used in further breeding studies to identify new sources of resistance to powdery mildew.

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Disruption of barley immunity to powdery mildew by an in-frame Lys-Leu deletion in the essential protein SGT1

Genetics ◽

10.1093/genetics/iyaa026 ◽

2020 ◽

Vol 217 (2) ◽

Cited By ~ 1

Author(s):

Antony V E Chapman ◽

Matthew Hunt ◽

Priyanka Surana ◽

Valeria Velásquez-Zapata ◽

Weihui Xu ◽

...

Keyword(s):

Powdery Mildew ◽

Fungal Pathogens ◽

Novel Mutation ◽

Exome Capture ◽

Resistance Locus ◽

Hordeum Vulgare L ◽

Powdery Mildew Fungus ◽

Pathogen Effectors ◽

Cell Processes ◽

Disease Resistances

Abstract Barley (Hordeum vulgare L.) Mla (Mildew resistance locus a) and its nucleotide-binding, leucine-rich-repeat receptor (NLR) orthologs protect many cereal crops from diseases caused by fungal pathogens. However, large segments of the Mla pathway and its mechanisms remain unknown. To further characterize the molecular interactions required for NLR-based immunity, we used fast-neutron mutagenesis to screen for plants compromised in MLA-mediated response to the powdery mildew fungus, Blumeria graminis f. sp. hordei. One variant, m11526, contained a novel mutation, designated rar3 (required for Mla6 resistance3), that abolishes race-specific resistance conditioned by the Mla6, Mla7, and Mla12 alleles, but does not compromise immunity mediated by Mla1, Mla9, Mla10, and Mla13. This is analogous to, but unique from, the differential requirement of Mla alleles for the co-chaperone Rar1 (required for Mla12 resistance1). We used bulked-segregant-exome capture and fine mapping to delineate the causal mutation to an in-frame Lys-Leu deletion within the SGS domain of SGT1 (Suppressor of G-two allele of Skp1, Sgt1ΔKL308–309), the structural region that interacts with MLA proteins. In nature, mutations to Sgt1 usually cause lethal phenotypes, but here we pinpoint a unique modification that delineates its requirement for some disease resistances, while unaffecting others as well as normal cell processes. Moreover, the data indicate that the requirement of SGT1 for resistance signaling by NLRs can be delimited to single sites on the protein. Further study could distinguish the regions by which pathogen effectors and host proteins interact with SGT1, facilitating precise editing of effector incompatible variants.

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Nod-Like Receptors in Host Defence and Disease at the Epidermal Barrier

International Journal of Molecular Sciences ◽

10.3390/ijms22094677 ◽

2021 ◽

Vol 22 (9) ◽

pp. 4677

Author(s):

Judit Danis ◽

Mark Mellett

Keyword(s):

Immune Response ◽

Tissue Expression ◽

Inflammasome Activation ◽

Nucleotide Binding Domain ◽

Microbial Infection ◽

Epidermal Barrier ◽

The Family ◽

Bona Fide ◽

Activation Antigen

The nucleotide-binding domain and leucine-rich-repeat-containing family (NLRs) (sometimes called the NOD-like receptors, though the family contains few bona fide receptors) are a superfamily of multidomain-containing proteins that detect cellular stress and microbial infection. They constitute a critical arm of the innate immune response, though their functions are not restricted to pathogen recognition and members engage in controlling inflammasome activation, antigen-presentation, transcriptional regulation, cell death and also embryogenesis. NLRs are found from basal metazoans to plants, to zebrafish, mice and humans though functions of individual members can vary from species to species. NLRs also display highly wide-ranging tissue expression. Here, we discuss the importance of NLRs to the immune response at the epidermal barrier and summarise the known role of individual family members in the pathogenesis of skin disease.

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First Report of Powdery Mildew Caused by Erysiphe aquilegiae var. aquilegiae on Aquilegia flabellata in Italy

Plant Disease ◽

10.1094/pdis.2004.88.6.681a ◽

2004 ◽

Vol 88 (6) ◽

pp. 681-681

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

United States ◽

Powdery Mildew ◽

The United States ◽

Northern Italy ◽

American Phytopathological Society ◽

First Report ◽

Powdery Mildews ◽

The Family ◽

White Mycelium ◽

The University

Aquilegia flabellata Sieb. and Zucc. (columbine) is a perennial garden species belonging to the family Ranunculaceae. During the summer of 2003, a severe outbreak of a previously unknown powdery mildew was observed in several gardens near Biella (northern Italy). Upper surfaces of leaves were covered with a white mycelium and conidia, and as the disease progressed infected leaves turned yellow and died. Foot cell was cylindric and appressorium lobed. Conidia were hyaline, ellipsoid, and measured 31.2 to 47.5 × 14.4 to 33 μm (average 38.6 × 21.6 μm). Fibrosin bodies were not present. Cleistothecia were globose, brown, had simple appendages, ranged from 82 to 127 (average 105) μm in diameter, and contained one to two asci. Ascocarp appendages measured five to eight times the ascocarp diameter. Asci were cylindrical (ovoidal) and measured 45.3 to 58.2 × 30.4 to 40.2 μm. Ascospores (three to four per ascus) were ellipsoid or cylindrical and measured 28.3 to 31.0 × 14.0 to 15.0 μ;m. On the basis of its morphology, the pathogen was identified as Erysiphe aquilegiae var. aquilegiae (1). Pathogenicity was confirmed by gently pressing diseased leaves onto leaves of five, healthy A. flabellata plants. Five noninoculated plants served as controls. Inoculated and noninoculated plants were maintained in a garden where temperatures ranged between 20 and 30°C. After 10 days, typical powdery mildew symptoms developed on inoculated plants. Noninoculated plants did not show symptoms. To our knowledge, this is the first report of the presence of powdery mildew on Aquilegia flabellata in Italy. E. communis (Wallr.) Link and E. polygoni DC. were reported on several species of Aquilegia in the United States (2), while E. aquilegiae var. aquilegiae was previously observed on A. flabellata in Japan and the former Union of Soviet Socialist Republics (3). Specimens of this disease are available at the DIVAPRA Collection at the University of Torino. References: (1) U. Braun. Nova Hedwigia, 89:700, 1987. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St Paul, MN, 1989. (3) K. Hirata. Host Range and Geographical Distribution of the Powdery Mildews. Faculty of Agriculture, Niigata University, 1966.

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LRRpredictor—A New LRR Motif Detection Method for Irregular Motifs of Plant NLR Proteins Using an Ensemble of Classifiers

Genes ◽

10.3390/genes11030286 ◽

2020 ◽

Vol 11 (3) ◽

pp. 286 ◽

Cited By ~ 3

Author(s):

Eliza C. Martin ◽

Octavina C. A. Sukarta ◽

Laurentiu Spiridon ◽

Laurentiu G. Grigore ◽

Vlad Constantinescu ◽

...

Keyword(s):

Protein Interactions ◽

Structural Data ◽

Innate Immune ◽

Protein Protein Interactions ◽

Ensemble Of Classifiers ◽

Immune Receptor ◽

Motif Detection ◽

Protein Architecture ◽

Recognition Specificity ◽

Leucine Rich Repeats

Leucine-rich-repeats (LRRs) belong to an archaic procaryal protein architecture that is widely involved in protein–protein interactions. In eukaryotes, LRR domains developed into key recognition modules in many innate immune receptor classes. Due to the high sequence variability imposed by recognition specificity, precise repeat delineation is often difficult especially in plant NOD-like Receptors (NLRs) notorious for showing far larger irregularities. To address this problem, we introduce here LRRpredictor, a method based on an ensemble of estimators designed to better identify LRR motifs in general but particularly adapted for handling more irregular LRR environments, thus allowing to compensate for the scarcity of structural data on NLR proteins. The extrapolation capacity tested on a set of annotated LRR domains from six immune receptor classes shows the ability of LRRpredictor to recover all previously defined specific motif consensuses and to extend the LRR motif coverage over annotated LRR domains. This analysis confirms the increased variability of LRR motifs in plant and vertebrate NLRs when compared to extracellular receptors, consistent with previous studies. Hence, LRRpredictor is able to provide novel insights into the diversification of LRR domains and a robust support for structure-informed analyses of LRRs in immune receptor functioning.

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Expression of the Membrane-Associated Resistance Protein RPW8 Enhances Basal Defense Against Biotrophic Pathogens

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-20-8-0966 ◽

2007 ◽

Vol 20 (8) ◽

pp. 966-976 ◽

Cited By ~ 69

Author(s):

Wenming Wang ◽

Alessandra Devoto ◽

John G. Turner ◽

Shunyuan Xiao

Keyword(s):

Salicylic Acid ◽

Powdery Mildew ◽

Fungal Pathogens ◽

Coiled Coil ◽

Small Gtpase ◽

Cauliflower Mosaic Virus ◽

R Genes ◽

Amino Terminal ◽

Small Proteins ◽

Enhanced Resistance

The powdery mildew resistance genes RPW8.1 and RPW8.2 from Arabidopsis differ from the other isolated plant resistance (R) genes in their predicted protein domains and their resistance spectrum. The two homologous RPW8 genes encode small proteins featuring a predicted amino-terminal transmembrane anchor domain and a coiled-coil domain and confer resistance to a broad spectrum of powdery mildews. Here, we show that Arabidopsis plants expressing the RPW8 genes have enhanced resistance to another biotrophic pathogen, Hyaloperonospora parasitica, raising the possibility that the RPW8 genes may function to enhance salicylic-acid-dependent basal defenses, rather than as powdery-mildew-specific R genes. When overexpressed from their native promoters, the RPW8 genes confer enhanced resistance to the Cauliflower mosaic virus, but render plants more susceptible to the necrotrophic fungal pathogens Alternaria and Botrytis spp. Furthermore, we show that the RPW8 proteins appear to be localized to the endomembrane system, overlapping with the endoplasmic reticulum–associated small GTPase SAR1, and accumulate to higher levels in response to application of exogenous salicylic acid, one of the signaling molecules of plant defense.

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Structure and evolutionary history of a large family of NLR proteins in the zebrafish

Open Biology ◽

10.1098/rsob.160009 ◽

2016 ◽

Vol 6 (4) ◽

pp. 160009 ◽

Cited By ~ 56

Author(s):

Kerstin Howe ◽

Philipp H. Schiffer ◽

Julia Zielinski ◽

Thomas Wiehe ◽

Gavin K. Laird ◽

...

Keyword(s):

Adaptive Immune System ◽

Large Family ◽

Immune Recognition ◽

Adaptive Immune ◽

New Family ◽

The Family ◽

History Of ◽

Leucine Rich Repeats ◽

Adaptive Immune Systems ◽

B30.2 Domain

Multicellular eukaryotes have evolved a range of mechanisms for immune recognition. A widespread family involved in innate immunity are the NACHT-domain and leucine-rich-repeat-containing (NLR) proteins. Mammals have small numbers of NLR proteins, whereas in some species, mostly those without adaptive immune systems, NLRs have expanded into very large families. We describe a family of nearly 400 NLR proteins encoded in the zebrafish genome. The proteins share a defining overall structure, which arose in fishes after a fusion of the core NLR domains with a B30.2 domain, but can be subdivided into four groups based on their NACHT domains. Gene conversion acting differentially on the NACHT and B30.2 domains has shaped the family and created the groups. Evidence of positive selection in the B30.2 domain indicates that this domain rather than the leucine-rich repeats acts as the pathogen recognition module. In an unusual chromosomal organization, the majority of the genes are located on one chromosome arm, interspersed with other large multigene families, including a new family encoding zinc-finger proteins. The NLR-B30.2 proteins represent a new family with diversity in the specific recognition module that is present in fishes in spite of the parallel existence of an adaptive immune system.

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A Pattern Recognition Tool for Quantitative Analysis of In Planta Hyphal Growth of Powdery Mildew Fungi

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-18-0906 ◽

2005 ◽

Vol 18 (9) ◽

pp. 906-912 ◽

Cited By ~ 15

Author(s):

U. Seiffert ◽

P. Schweizer

Keyword(s):

Growth Rate ◽

Pattern Recognition ◽

Quantitative Analysis ◽

Powdery Mildew ◽

Growth Rates ◽

Fungal Pathogens ◽

Hyphal Growth ◽

Blumeria Graminis ◽

In Planta ◽

Powdery Mildew Fungi

The development of fungal pathogens can be quantified easily at the level of spore germination or penetration. However, the exact quantification of hyphal growth rates after initial, successful host invasion is much more difficult. Here, we report on the development of a new pattern recognition software (HyphArea) for automated quantitative analysis of hyphal growth rates of powdery mildew fungi on plant surfaces that usually represent highly irregular and noisy image backgrounds. By using HyphArea, we measured growth rates of colonies of the barley powdery mildew, Blumeria graminis f. sp. hordei, on susceptible and induced-resistant host plants. Hyphal growth was not influenced by the resistance state of the plants up to 48 h postinoculation. At later time points, growth rate increased on susceptible plants, whereas it remained restricted on induced-resistant plants. This difference in hyphal growth rate was accompanied by lack of secondary haustoria formation on induced-resistant plants, suggesting that induced resistance in barley against Blumeria graminis is caused mainly by reduced penetration rates of primary as well as secondary appressoria leading, finally, to fewer and lessdeveloped fungal colonies. No evidence was found for reduced nutrient-uptake efficiency of the primary haustoria in induced-resistant leaves, which would be expected to have resulted in reduced hyphal growth rates during the first 48 h of the interaction.

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Host adaptation through hybridization: Genome analysis of triticale powdery mildew reveals unique combination of lineage-specific effectors

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-05-21-0111-sc ◽

2021 ◽

Author(s):

Marion Claudia Müller ◽

Lukas Kunz ◽

Johannes Peter Graf ◽

Seraina Schudel ◽

Beat Keller

Keyword(s):

Powdery Mildew ◽

Fungal Pathogens ◽

Genetic Basis ◽

Reference Genome ◽

Resistance Breeding ◽

Host Adaptation ◽

Allelic Series ◽

Hybrid Genome ◽

Long Read ◽

Bona Fide

The emergence of new fungal pathogens through hybridization represents a serious challenge for agriculture. Hybridization between the wheat mildew (Blumeria graminis f.sp. tritici) and rye mildew (B.g. f.sp. secalis) pathogens have led to the emergence of a new mildew form (B.g. f.sp. triticale) growing on triticale, a man-made amphiploid crop derived from crossing rye and wheat which was originally resistant to the powdery mildew disease. The identification of the genetic basis of host-adaptation in triticale mildew has been hampered by the lack of a reference genome. Here we report the 141.4 Mb reference assembly of triticale mildew isolate THUN-12 derived from long-read sequencing and genetic map-based scaffolding. All eleven triticale mildew chromosomes were assembled from telomere-to-telomere and revealed that 19.7% of the hybrid genome was inherited from the rye mildew parental lineage. We identified lineage-specific regions in the hybrid, inherited from the rye or wheat mildew parental lineages, that harbour numerous bona fide candidate effectors. We propose that the combination of lineage-specific effectors in the hybrid genome is crucial for host-adaptation, allowing the fungus to simultaneously circumvent the immune systems contributed by wheat and rye in the triticale crop. In line with this we demonstrate the functional transfer of the SvrPm3 effector from wheat to triticale mildew, a virulence effector that specifically suppresses resistance of the wheat Pm3 allelic series. This transfer is the likely underlying cause for the observed poor effectiveness of several Pm3 alleles against triticale mildew and exemplifies the negative implications of pathogen hybridizations on resistance breeding.

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Potential of genetic resistance of new table grape hybrids to fungal pathogens

BIO Web of Conferences ◽

10.1051/bioconf/20213402001 ◽

2021 ◽

Vol 34 ◽

pp. 02001

Author(s):

Elena Ilnitskaya ◽

Marina Makarkina ◽

Valeriy Petrov

Keyword(s):

Powdery Mildew ◽

Downy Mildew ◽

Resistance Genes ◽

Dna Markers ◽

Fungal Pathogens ◽

Genetic Resistance ◽

Plasmopara Viticola ◽

Table Grape ◽

Table Grapes ◽

Hybrid Forms

Downy mildew (Plasmopara viticola) and powdery mildew (Erysiphe necator) are the most common and economically significant fungal diseases in vineyards. The task of this work is to study the genotypes of new promising hybrid forms of table grapes for the presence of resistance genes to downy mildew (Rpv10 and Rpv3) and powdery mildew (Ren9) using DNA-markers. The study was carried out on table grape hybrids under the working names Agat dubovskiy, Akelo, Arabella, Artek, Dubovskiy rozovyi, Gamlet, Ispolin, Kishmish dubovskiy, Kurazh, Pestryi, Valensiya and registered variety Liviya. The studied genes were analyzed using markers UDV305 and UDV737 (Rpv3), GF09-46 (Rpv10), CenGen6 (Ren9). The following cultivars were used as reference genotypes: Saperavi severnyi (carries Rpv10 gene) and Regent (Rpv3 and Ren9). It was established that Rpv3 gene is carried by hybrids Kishmish dubovskiy, Agat dubovskiy, Kurazh, Valensiya, Akelo, Gamlet, Dubovskiy rozovyi, Pestryi. Ren9 gene was found in Artek, Agat dubovskiy, Kurazh, Ispolin, Valensiya, Arabella, Gamlet, Dubovskiy rozovyi, Pestryi. The Rpv10 gene was not detected in any of the analyzed grapevine samples. genotypes Agat dubovskiy, Kurazh, Gamlet, Dubovskiy rozovyi, Pestryi, Valensiya carry Rpv3 and Ren9 genes simultaneously. These grapevines have an elegant bunch and large berries that are attractive to consumers.

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