scholarly journals Allelic barley MLA immune receptors recognize sequence-unrelated avirulence effectors of the powdery mildew pathogen

2016 ◽  
Vol 113 (42) ◽  
pp. E6486-E6495 ◽  
Author(s):  
Xunli Lu ◽  
Barbara Kracher ◽  
Isabel M. L. Saur ◽  
Saskia Bauer ◽  
Simon R. Ellwood ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Gene Clusters ◽  
Specific Cell ◽  
Resistance Locus ◽  
Powdery Mildew Fungus ◽  
Evolutionarily Conserved ◽  
Genes Encoding ◽  
Barley Leaves ◽  
Allele Specific ◽  
Powdery Mildew Pathogen

Disease-resistance genes encoding intracellular nucleotide-binding domain and leucine-rich repeat proteins (NLRs) are key components of the plant innate immune system and typically detect the presence of isolate-specific avirulence (AVR) effectors from pathogens. NLR genes define the fastest-evolving gene family of flowering plants and are often arranged in gene clusters containing multiple paralogs, contributing to copy number and allele-specific NLR variation within a host species. Barley mildew resistance locus a (Mla) has been subject to extensive functional diversification, resulting in allelic resistance specificities each recognizing a cognate, but largely unidentified, AVRa gene of the powdery mildew fungus, Blumeria graminis f. sp. hordei (Bgh). We applied a transcriptome-wide association study among 17 Bgh isolates containing different AVRa genes and identified AVRa1 and AVRa13, encoding candidate-secreted effectors recognized by Mla1 and Mla13 alleles, respectively. Transient expression of the effector genes in barley leaves or protoplasts was sufficient to trigger Mla1 or Mla13 allele-specific cell death, a hallmark of NLR receptor-mediated immunity. AVRa1 and AVRa13 are phylogenetically unrelated, demonstrating that certain allelic MLA receptors evolved to recognize sequence-unrelated effectors. They are ancient effectors because corresponding loci are present in wheat powdery mildew. AVRA1 recognition by barley MLA1 is retained in transgenic Arabidopsis, indicating that AVRA1 directly binds MLA1 or that its recognition involves an evolutionarily conserved host target of AVRA1. Furthermore, analysis of transcriptome-wide sequence variation among the Bgh isolates provides evidence for Bgh population structure that is partially linked to geographic isolation.

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 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 Multivesicular compartments proliferate in susceptible and resistant MLA12-barley leaves in response to infection by the biotrophic powdery mildew fungus

2006 ◽  
Vol 172 (3) ◽  
pp. 563-576 ◽  
Author(s):  
Qianli An ◽  
Katrin Ehlers ◽  
Karl-Heinz Kogel ◽  
Aart J. E. van Bel ◽  
Ralph Hückelhoven
Keyword(s):  
Powdery Mildew ◽  
Powdery Mildew Fungus ◽  
Barley Leaves

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 Evidence for Allele-Specific Levels of Enhanced Susceptibility of Wheat mlo Mutants to the Hemibiotrophic Fungal Pathogen Magnaporthe oryzae pv. Triticum

Genes ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 517 ◽  
Author(s):  
Katrin Gruner ◽  
Tobias Esser ◽  
Johanna Acevedo-Garcia ◽  
Matthias Freh ◽  
Michael Habig ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Magnaporthe Oryzae ◽  
Blast Disease ◽  
Transcription Activator ◽  
Zymoseptoria Tritici ◽  
Mesophyll Cells ◽  
Septoria Leaf Blotch ◽  
Partial Protection ◽  
Allele Specific ◽  
Powdery Mildew Pathogen

Barley mlo mutants are well known for their profound resistance against powdery mildew disease. Recently, mlo mutant plants were generated in hexaploid bread wheat (Triticum aestivum) with the help of transgenic (transcription-activator-like nuclease, TALEN) and non-transgenic (targeted induced local lesions in genomes, TILLING) biotechnological approaches. While full-gene knockouts in the three wheat Mlo (TaMlo) homoeologs, created via TALEN, confer full resistance to the wheat powdery mildew pathogen (Blumeria graminis f.sp. tritici), the currently available TILLING-derived Tamlo missense mutants provide only partial protection against powdery mildew attack. Here, we studied the infection phenotypes of TALEN- and TILLING-derived Tamlo plants to the two hemibiotrophic pathogens Zymoseptoria tritici, causing Septoria leaf blotch in wheat, and Magnaporthe oryzae pv. Triticum (MoT), the causal agent of wheat blast disease. While Tamlo plants showed unaltered outcomes upon challenge with Z. tritici, we found evidence for allele-specific levels of enhanced susceptibility to MoT, with stronger powdery mildew resistance correlated with more invasive growth by the blast pathogen. Surprisingly, unlike barley mlo mutants, young wheat mlo mutant plants do not show undesired pleiotropic phenotypes such as spontaneous callose deposits in leaf mesophyll cells or signs of early leaf senescence. In conclusion, our study provides evidence for allele-specific levels of enhanced susceptibility of Tamlo plants to the hemibiotrophic wheat pathogen MoT.

scholarly journals Experiments to examine the significance of ammonia evolution from barley seedlings infected with the powdery mildew fungus, Erysiphe graminis f.sp. hordei

1984 ◽  
Vol 102 (3) ◽  
pp. 679-685 ◽  
Author(s):  
J. F. Jenkyn ◽  
M. E. Finney
Keyword(s):  
Powdery Mildew ◽  
Significant Proportion ◽  
Ammonium Nitrogen ◽  
Erysiphe Graminis ◽  
Powdery Mildew Fungus ◽  
Subsequent Evolution ◽  
Ammonia Gas ◽  
Soil Systems ◽  
Detached Leaves ◽  
Barley Leaves

SummaryExperiments using intact seedlings and detached leaves failed to confirm previous reports that ammonia gas is evolved from barley leaves during the establishment of infection by the powdery mildew fungus Erysiphe graminis f.sp. hordei.In the experiments using intact seedlings infection did, however, lead to greater concentrations of ammonium nitrogen in the senescing leaves and, in one experiment, the subsequent evolution of ammonia gas from these seedlings. Losses of nitrogen as ammonia gas from crops are probably small, but it is possible that under some circumstances they may represent a significant proportion of the otherwise unexplained nitrogen losses and hence be important in experiments which aim to study the nitrogen balance of crop-soil systems.

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