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

Genetics ◽  
2020 ◽  
Vol 217 (2) ◽  
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.

scholarly journals Diversity at the Mla Powdery Mildew Resistance Locus from Cultivated Barley Reveals Sites of Positive Selection

2010 ◽  
Vol 23 (4) ◽  
pp. 497-509 ◽  
Author(s):  
Sabine Seeholzer ◽  
Takashi Tsuchimatsu ◽  
Tina Jordan ◽  
Stéphane Bieri ◽  
Simone Pajonk ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Positive Selection ◽  
Transient Gene Expression ◽  
Coiled Coil ◽  
Resistance Locus ◽  
Powdery Mildew Fungus ◽  
Genetic Studies ◽  
Mla Locus ◽  
Or Gene ◽  
Positively Selected Sites

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.

scholarly journals SGT1 SGS-domain mutations impair interactions with the barley MLA6 immune receptor in association with loss of NLR protein

2021 ◽  
Author(s):  
Antony Chapman ◽  
James Mitch Elmore ◽  
Maxwell McReynolds ◽  
Justin Walley ◽  
Roger Philip Wise
Keyword(s):  
Fungal Pathogens ◽  
Coiled Coil ◽  
Heat Shock Protein 90 ◽  
Intramolecular Interactions ◽  
Protein Accumulation ◽  
Resistance Locus ◽  
Hordeum Vulgare L ◽  
Resistance Proteins ◽  
Concomitant Reduction ◽  
Two Hybrid

The Mla (Mildew resistance locus a) of barley (Hordeum vulgare L.) is an effective model for cereal immunity against fungal pathogens. Like many resistance proteins, variants of the MLA coiled-coil nucleotide-binding leucine-rich-repeat (CC-NLR) receptor require the HRS complex to function, which includes HSP90 (Heat Shock Protein 90), RAR1 (Required for Mla12 Resistance 1), and SGT1 (Suppressor of G-two allele of Skp1). However, functional analysis of Sgt1 has been particularly difficult as deletions are often lethal. Recently, we identified rar3 (Required for Mla6 resistance 3), an in-frame Sgt1ΔKL308-309 mutation in the SGS domain that alters resistance conferred by MLA, but without lethality. Here we use autoactive MLA6 and heterologous yeast-two-hybrid strains with stably integrated HvRar1 and HvHsp90, to determine that this mutation weakens, but doesn’t entirely disrupt, the interaction between SGT1 and MLA. This causes a concomitant reduction in MLA6 protein accumulation below the apparent threshold required for effective resistance. The ΔKL308-309 deletion had a lesser effect on intramolecular interactions than alanine or arginine substitutions, and MLA variants that display diminished interactions with SGT1 appear to be disproportionately affected by the SGT1ΔKL308-309 mutation. We hypothesize that those dimeric plant CC-NLRs that appear unaffected by Sgt1 silencing are those with the strongest intermolecular interactions with it. Combining our data with recent work in CC-NLRs, we propose a cyclical model of the MLA-HRS resistosome interactions.

scholarly journals The Mycorrhiza Fungus Piriformospora indica Induces Fast Root-Surface pH Signaling and Primes Systemic Alkalinization of the Leaf Apoplast Upon Powdery Mildew Infection

2009 ◽  
Vol 22 (9) ◽  
pp. 1179-1185 ◽  
Author(s):  
Hubert H. Felle ◽  
Frank Waller ◽  
Alexandra Molitor ◽  
Karl-Heinz Kogel
Keyword(s):  
Powdery Mildew ◽  
Piriformospora Indica ◽  
Plant Responses ◽  
Hordeum Vulgare L ◽  
Powdery Mildew Fungus ◽  
Surface Ph ◽  
Apoplastic Ph ◽  
Elicitor Response ◽  
Ph Increase ◽  
Leaf Apoplast

We analyze here, by noninvasive electrophysiology, local and systemic plant responses in the interaction of barley (Hordeum vulgare L.) with the root-colonizing basidiomycete Piriformospora indica. In the short term (seconds, minutes), a constant flow of P. indica chlamydospores along primary roots altered surface pH characteristics; whereas the root-hair zone transiently alkalized—a typical elicitor response—the elongation zone acidified, indicative of enhanced H+ extrusion and plasma membrane H+ ATPase stimulation. Eight to 10 min after treating roots with chlamydospores, the apoplastic pH of leaves began to acidify, which contrasts with observations of an alkalinization response to various stressors and microbe-associated molecular patterns (MAMPs). In the long term (days), plants with P. indica-colonized roots responded to inoculation with the leaf-pathogenic powdery mildew fungus Blumeria graminis f. sp. hordei with a leaf apoplastic pH increase of about 2, while the leaf apoplast of noncolonized barley responded to B. graminis f. sp. hordei merely with a pH increase of 0.8. The strong apoplastic pH response is reminiscent of B. graminis f. sp. hordei–triggered pH shifts in resistance gene–mediated resistant barley leaves or upon treatment with a chemical resistance inducer. In contrast, the MAMP N-acetylchito-octaose did not induce resistance to B. graminis f. sp. hordei and did not trigger the primed apoplastic pH shift. We speculate that the primed pH increase is indicative of and supports the potentiated systemic response to B. graminis f. sp. hordei–induced by P. indica in barley.

Reconstitution of cyanogenesis in barley (Hordeum vulgare L.) and its implications for resistance against the barley powdery mildew fungus

Planta ◽  
2005 ◽  
Vol 223 (5) ◽  
pp. 1010-1023 ◽  
Author(s):  
Kirsten A. Nielsen ◽  
Maria Hrmova ◽  
Janni Nyvang Nielsen ◽  
Karin Forslund ◽  
Stefan Ebert ◽  
...  
Keyword(s):  
Hordeum Vulgare ◽  
Powdery Mildew ◽  
Hordeum Vulgare L ◽  
Powdery Mildew Fungus ◽  
Barley Powdery Mildew

Recombination of alleles conferring specific resistance to powdery mildew at the Mla locus in barley

Genome ◽  
1994 ◽  
Vol 37 (3) ◽  
pp. 460-468 ◽  
Author(s):  
Mamatha Mahadevappa ◽  
Richard A. DeScenzo ◽  
Roger P. Wise
Keyword(s):  
Powdery Mildew ◽  
Storage Proteins ◽  
Specific Resistance ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Genetic Distances ◽  
Hordeum Vulgare L ◽  
Powdery Mildew Fungus ◽  
Barley Powdery Mildew ◽  
Mla Locus

In barley (Hordeum vulgare L.), the Mla locus conditions reaction to the powdery mildew fungus Erysiphe graminis f.sp. hordei. Enrichment for genetic recombinants in the Mla region is possible by screening for recombination events between the flanking endosperm storage proteins hordeins C and B. Reciprocal crosses were made between the Franger (C.I. 16151) and Rupee (C.I. 16155) lines carrying the (Mla6 + Mla14) and Mla13 alleles, respectively. Recombinants were identified from F2 segregants by analyzing the extracted hordein polypeptides by sodium dodecyl sulphate – polyacrylamide gel electrophoresis. Two hundred and seventy-six recombinant gametes were identified from the 1800 seeds that were screened. Recombination of Mla alleles was analyzed by inoculating F4 recombinant lines with three isolates of E. graminis (A27, 5874, and CR3), which recognize specific Mla alleles. The linkage order established is Hor1–Mla6–Mla13–Mla14–Hor2. The genetic distances between Hor1–Mla6, Mla6–Mla13, and Mla13–Hor2, obtained using Mapmaker 3.0b F3 intercross analysis, are 3.9, 0.2, and 5.2 cM, respectively.Key words: recombinant, barley, powdery mildew, Mla, hordein.

scholarly journals Expression Pattern Analysis of Four Mlo Genes from Rose

2015 ◽  
Vol 140 (4) ◽  
pp. 333-338 ◽  
Author(s):  
Xianqin Qiu ◽  
Hongying Jian ◽  
Qigang Wang ◽  
Kaixue Tang ◽  
Manzhu Bao
Keyword(s):  
Powdery Mildew ◽  
Quantitative Polymerase Chain Reaction ◽  
Expression Patterns ◽  
Early Time ◽  
Resistance Locus ◽  
Loss Of Function ◽  
Powdery Mildew Fungus ◽  
Mildew Resistance ◽  
Powdery Mildew Pathogen ◽  
External Stimuli

Rose (Rosa hybrida) is one of the most economically important ornamentals worldwide. Powdery mildew (Podosphaera pannosa) is a major disease in cut and potted roses. In dicots such as arabidopsis (Arabidopsis thaliana), pea (Pisum sativum), and tomato (Solanum lycopersicum), loss-of-function mutations in mildew resistance locus o (Mlo) genes confer high levels of broad-spectrum resistance to powdery mildew. Here, we present spatiotemporal expression patterns of four Mlo genes from R. hybrida based on real-time fluorescence quantitative polymerase chain reaction (qPCR). Phylogenetically closely related R. hybrida mildew resistance locus o (RhMLO) genes showed similar or overlapping tissue specificity and analogous responsiveness to external stimuli. RhMLO1 and RhMLO2 transcriptional levels were upregulated more than 2-fold by external stimuli, especially by inoculation with powdery mildew fungus P. pannosa at early time points. This phenomenon was not found for RhMLO3 or RhMLO4. The results indicated that RhMLO1 and RhMLO2 might play important roles in rose–powdery mildew pathogen interactions. Our findings may provide useful information for the study of mechanisms of powdery mildew susceptibility in rose.

scholarly journals Apoplastic pH Signaling in Barley Leaves Attacked by the Powdery Mildew Fungus Blumeria graminis f. sp. hordei

2004 ◽  
Vol 17 (1) ◽  
pp. 118-123 ◽  
Author(s):  
Hubert H. Felle ◽  
Almut Herrmann ◽  
Stefan Hanstein ◽  
Ralph Hückelhoven ◽  
Karl-Heinz Kogel
Keyword(s):  
Powdery Mildew ◽  
Hypersensitive Reaction ◽  
Blumeria Graminis ◽  
Short Term ◽  
Hordeum Vulgare L ◽  
Powdery Mildew Fungus ◽  
Apoplastic Ph ◽  
Host Defense Response ◽  
Barley Leaves

To investigate apoplastic responses of barley (Hordeum vulgare L.) to the barley powdery mildew fungus Blumeria graminis f. sp. hordei, noninvasive microprobe techniques were employed. H+- and Ca2+-selective microprobes were inserted into open stomata of barley leaves inoculated with Blumeria graminis f. sp. hordei race A6 conidia. Resistance gene-mediated responses of barley genotype Ingrid (susceptible parent line) and the near-isogenic resistant Ingrid backcross lines (I-mlo5, I-Mla12, and I-Mlg) were continuously monitored from 20 min to 4 days after inoculation. The main events were categorized as short-term responses around 2 h after inoculation (hai), intermediate responses around 8 and 12 hai, and long-term responses starting between 21 and 24 hai. Short-term responses were rapid transient decreases of apoplastic H+- and Ca2+ activities that lasted minutes only. Kinetics were similar for all genotypes tested, and thus, these short-term responses were attributed as nonspecific first encounters of fungal surface material with the host plasma membrane. This is supported by the observation that a microinjected chitin oligomer (GlcNAc)8 yielded similar apoplastic alkalinization. Intermediate responses are trains of H+ (increase) spikes that, being different in susceptible Ingrid and penetration-resistant I-mlo5 (or I-Mlg), were interpreted as accompanying specific events of papillae formation. Long-term events were massive slow and long-lasting alkalinizations up to two pH units above control. Since these latter changes were only observed with near-isogenic hypersensitive reaction (HR)-mounting genotypes I-Mla12 and I-Mlg but not with I-mlo5 or, to a smaller extent, with susceptible Ingrid, both lacking significant rates of HR, they were rated as cell death specific. It is concluded that apoplastic pH changes are important indicators of host-pathogen interactions that correlate with both the different stages of fungal development and the different types of host defense response.

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