The Parastagonospora nodorum necrotrophic effector SnTox5 targets the wheat gene Snn5 and facilitates entry into the leaf mesophyll

Abstract Tan spot and Septoria nodorum blotch (SNB) are important diseases of wheat caused by the necrotrophic fungi Pyrenophora tritici-repentis and Parastagonospora nodorum, respectively. The P. tritici-repentis necrotrophic effector (NE) Ptr ToxB causes tan spot when recognized by the Tsc2 gene. The NE ToxA is produced by both pathogens and has been associated with the development of both tan spot and SNB when recognized by the wheat Tsn1 gene. Most work to study these interactions has been conducted in common wheat, but little has been done in durum wheat. Here, quantitative trait loci (QTL) analysis of a segregating biparental population indicated that the Tsc2-Ptr ToxB interaction plays a prominent role in the development of tan spot in durum. However, analysis of two biparental populations indicated that the Tsn1-ToxA interaction was not associated with the development of tan spot, but was strongly associated with the development of SNB. Pa. nodorum expressed ToxA at high levels in infected Tsn1 plants, whereas ToxA expression in P. tritici-repentis was barely detectable, suggesting that the differences in disease levels associated with the Tsn1-ToxA interaction were due to differences in pathogen expression of ToxA. These and previous results together indicate that: (1) the effects of Tsn1-ToxA on tan spot in common wheat can range from nonsignificant to highly significant depending on the host genetic background; (2) Tsn1-ToxA is not a significant factor for tan spot development in durum wheat; and (3) Tsn1-ToxA plays a major role in SNB development in both common and durum wheat. Durum and common wheat breeders alike should strive to remove both Tsc2 and Tsn1 from their materials to achieve disease resistance.

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The Wheat Snn7 Gene Confers Susceptibility on Recognition of the Parastagonospora nodorum Necrotrophic Effector SnTox7

The Plant Genome ◽

10.3835/plantgenome2015.02.0007 ◽

2015 ◽

Vol 8 (2) ◽

Cited By ~ 23

Author(s):

Gongjun Shi ◽

Timothy L. Friesen ◽

Jyoti Saini ◽

Steven S. Xu ◽

Jack B. Rasmussen ◽

...

Keyword(s):

Parastagonospora Nodorum ◽

Necrotrophic Effector

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Fine-Mapping the Wheat Snn1 Locus Conferring Sensitivity to the Parastagonospora nodorum Necrotrophic Effector SnTox1 Using an Eight Founder Multiparent Advanced Generation Inter-Cross Population

G3 Genes|Genome|Genetics ◽

10.1534/g3.115.021584 ◽

2015 ◽

Vol 5 (11) ◽

pp. 2257-2266 ◽

Cited By ~ 10

Author(s):

James Cockram ◽

Alice Scuderi ◽

Toby Barber ◽

Eiko Furuki ◽

Keith A. Gardner ◽

...

Keyword(s):

Fine Mapping ◽

Parastagonospora Nodorum ◽

Necrotrophic Effector ◽

Advanced Generation

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The necrotrophic effector ToxA from Parastagonospora nodorum interacts with wheat NHL proteins to facilitate Tsn1-mediated necrosis

10.1101/2021.09.22.461440 ◽

2021 ◽

Author(s):

Bayantes Dagvadorj ◽

Megan A. Outram ◽

Simon J. Williams ◽

Peter S. Solomon

Keyword(s):

Cell Death ◽

Confocal Microscopy ◽

Molecular Mechanisms ◽

Wheat Cultivars ◽

In Planta ◽

Yeast Two Hybrid ◽

Induce Cell Death ◽

Parastagonospora Nodorum ◽

Necrotrophic Effector ◽

Two Hybrid

SummaryThe plant pathogen Parastagonospora nodorum secretes necrotrophic effectors to promote disease. These effectors induce cell death on wheat cultivars carrying dominant susceptibility genes in an inverse gene-for-gene manner. However, the molecular mechanisms underpinning these interactions and resulting cell death remain unclear. Here, we used a yeast-two-hybrid library approach to identify wheat proteins that interact with the necrotrophic effector ToxA. Using this strategy, we identified an interaction between ToxA and a wheat transmembrane NDR/HIN1-like protein (TaNHL10) and confirmed the interaction using in-planta co-immunoprecipitation and confocal microscopy co-localization analysis. We showed that the C-terminus of TaNHL10 is extracellular whilst the N-terminus was localized in the cytoplasm. Further analyses using yeast-two-hybrid and confocal microscopy co-localization showed that ToxA interacts with the C-terminal LEA2 extracellular domain of TaNHL10. Random mutagenesis was then used to identify a ToxA mutant, ToxAN109D, which was unable to interact with TaNHL10 in yeast-two-hybrid assays. Subsequent heterologous expression and purification of ToxAN109D in Nicotiania benthamiana revealed that the mutated protein was unable to induce necrosis on Tsn1-dominant wheat cultivars confirming that the interaction of ToxA with TaNHL10 is required to induce cell death. Collectively, these data advance our understanding on how ToxA induces cell death during infection and further highlights the importance of host cell surface interactions in necrotrophic pathosystems.

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ToxA–Tsn1 Interaction for Spot Blotch Susceptibility in Indian Wheat: An Example of Inverse Gene-for-Gene Relationship

Plant Disease ◽

10.1094/pdis-05-19-1066-re ◽

2020 ◽

Vol 104 (1) ◽

pp. 71-81 ◽

Cited By ~ 6

Author(s):

Sudhir Navathe ◽

Punam Singh Yadav ◽

Ramesh Chand ◽

Vinod Kumar Mishra ◽

Neeraj Kumar Vasistha ◽

...

Keyword(s):

Fungal Pathogens ◽

Bipolaris Sorokiniana ◽

Spot Blotch ◽

Wheat Cultivars ◽

Pyrenophora Tritici Repentis ◽

Necrotic Spots ◽

Parastagonospora Nodorum ◽

Necrotrophic Effector ◽

Selection Of ◽

Gene For Gene

The ToxA–Tsn1 system is an example of an inverse gene-for-gene relationship. The gene ToxA encodes a host-selective toxin (HST) which functions as a necrotrophic effector and is often responsible for the virulence of the pathogen. The genomes of several fungal pathogens (e.g., Pyrenophora tritici-repentis, Parastagonospora nodorum, and Bipolaris sorokiniana) have been shown to carry the ToxA gene. Tsn1 is a sensitivity gene in the host, whose presence generally helps a ToxA-positive pathogen to cause spot blotch in wheat. Cultivars lacking Tsn1 are generally resistant to spot blotch; this resistance is attributed to a number of other known genes which impart resistance in the absence of Tsn1. In the present study, 110 isolates of B. sorokiniana strains, collected from the ME5A and ME4C megaenvironments of India, were screened for the presence of the ToxA gene; 77 (70%) were found to be ToxA positive. Similarly, 220 Indian wheat cultivars were screened for the presence of the Tsn1 gene; 81 (36.8%) were found to be Tsn1 positive. When 20 wheat cultivars (11 with Tsn1 and 9 with tsn1) were inoculated with ToxA-positive isolates, seedlings of only those carrying the Tsn1 allele (not tsn1) developed necrotic spots surrounded by a chlorotic halo. No such distinction between Tsn1 and tsn1 carriers was observed when adult plants were inoculated. This study suggests that the absence of Tsn1 facilitated resistance against spot blotch of wheat. Therefore, the selection of wheat genotypes for the absence of the Tsn1 allele can improve resistance to spot blotch.

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Validation of Genome-Wide Association Studies as a Tool to Identify Virulence Factors in Parastagonospora nodorum

Phytopathology ◽

10.1094/phyto-02-16-0113-fi ◽

2016 ◽

Vol 106 (10) ◽

pp. 1177-1185 ◽

Cited By ~ 28

Author(s):

Yuanyuan Gao ◽

Zhaohui Liu ◽

Justin D. Faris ◽

Jonathan Richards ◽

Robert S. Brueggeman ◽

...

Keyword(s):

Association Studies ◽

Polymerase Chain Reaction Amplification ◽

Genome Wide Association ◽

Genome Wide Association Studies ◽

The Novel ◽

Gene Markers ◽

Genome Wide ◽

Parastagonospora Nodorum ◽

Genomic Regions ◽

Necrotrophic Effector

Parastagonospora nodorum is a necrotrophic fungal pathogen causing Septoria nodorum blotch on wheat. We have identified nine necrotrophic effector–host dominant sensitivity gene interactions, and we have cloned three of the necrotrophic effector genes, including SnToxA, SnTox1, and SnTox3. Because sexual populations of P. nodorum are difficult to develop under lab conditions, genome-wide association study (GWAS) is the best population genomic approach to identify genomic regions associated with traits using natural populations. In this article, we used a global collection of 191 P. nodorum isolates from which we identified 2,983 single-nucleotide polymorphism (SNP) markers and gene markers for SnToxA and SnTox3 to evaluate the power of GWAS on two popular wheat breeding lines that were sensitive to SnToxA and SnTox3. Strong marker trait associations (MTA) with P. nodorum virulence that mapped to SnTox3 and SnToxA were first identified using the marker set described above. A novel locus in the P. nodorum genome associated with virulence was also identified as a result of this analysis. To evaluate whether a sufficient level of marker saturation was available, we designed a set of primers every 1 kb in the genomic regions containing SnToxA and SnTox3. Polymerase chain reaction amplification was performed across the 191 isolates and the presence/absence polymorphism was scored and used as the genotype. The marker proximity necessary to identify MTA flanking SnToxA and SnTox3 ranged from 4 to 5 and 1 to 7 kb, respectively. Similar analysis was performed on the novel locus. Using a 45% missing data threshold, two more SNP were identified spanning a 4.6-kb genomic region at the novel locus. These results showed that the rate of linkage disequilibrium (LD) decay in P. nodorum and, likely, other fungi is high compared with plants and animals. The fast LD decay in P. nodorum is an advantage only if sufficient marker density is attained. Based on our results with the SnToxA and SnTox3 regions, markers are needed every 9 or 8 kb, respectively, or in every gene, to guarantee that genes associated with a quantitative trait such as virulence are not missed.

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The Parastagonospora nodorum necrotrophic effector SnTox5 targets the wheat gene Snn5 and facilitates entry into the leaf mesophyll

10.1101/2021.02.26.433117 ◽

2021 ◽

Author(s):

Gayan K. Kariyawasam ◽

Jonathan K. Richards ◽

Nathan A. Wyatt ◽

Katherine Running ◽

Steven S. Xu ◽

...

Keyword(s):

Genome Wide Association Study ◽

Susceptibility Gene ◽

Purifying Selection ◽

Chromosome 8 ◽

Secretion Signal ◽

Septoria Nodorum Blotch ◽

The Us ◽

Wheat Gene ◽

Amino Acid Secretion ◽

Parastagonospora Nodorum

AbstractParastagonospora nodorum, causal agent of septoria nodorum blotch, is a destructive necrotrophic fungal pathogen of wheat. P. nodorum is known to secrete several necrotrophic effectors that target wheat susceptibility genes that trigger classical biotrophic resistance responses but resulting in susceptibility rather than resistance. SnTox5 targets the wheat susceptibility gene Snn5 to induce necrosis. In this study, we used full genome sequences of 197 P. nodorum isolates collected from the US and their disease phenotyping on the Snn5 differential line LP29, to perform genome wide association study analysis to localize the SnTox5 gene to chromosome 8 of P. nodorum. SnTox5 was validated using gene transformation and CRISPR-Cas9 based gene disruption. SnTox5 encoded a small secreted protein with a 22 and 45 amino acid secretion signal and a pro sequence, respectively. The SnTox5 gene is under purifying selection in the Upper Midwest but under strong diversifying selection in the South/East regions of the US. Comparison of wild type and SnTox5-disrupted strains on wheat lines with and without the susceptibility target Snn5 showed that SnTox5 has two functions, 1) facilitating colonization of the mesophyll layer, and 2) targeting Snn5 to induce programmed cell death to provide cellular nutrient to complete its necrotrophic life cycle.

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Sensitivity to three Parastagonospora nodorum necrotrophic effectors in current Australian wheat cultivars and the presence of further fungal effectors

Crop and Pasture Science ◽

10.1071/cp13443 ◽

2014 ◽

Vol 65 (2) ◽

pp. 150 ◽

Cited By ~ 20

Author(s):

Kar-Chun Tan ◽

Ormonde D. C. Waters ◽

Kasia Rybak ◽

Eva Antoni ◽

Eiko Furuki ◽

...

Keyword(s):

Fungal Pathogen ◽

Gene Interactions ◽

Wheat Cultivars ◽

Septoria Nodorum Blotch ◽

Effector Genes ◽

Australian Wheat ◽

Parastagonospora Nodorum ◽

Necrotrophic Effector ◽

Necrotrophic Effectors ◽

Western Australian

Parastagonospora nodorum is a major fungal pathogen of wheat in Australia, causing septoria nodorum blotch (SNB). Virulence of P. nodorum is quantitative and depends largely on multiple effector–host sensitivity gene interactions. The pathogen utilises a series of proteinaceous, necrotrophic effectors to facilitate disease development on wheat cultivars that possess appropriate dominant sensitivity loci. Thus far, three necrotrophic effector genes have been cloned. Proteins derived from these genes were used to identify wheat cultivars that confer effector sensitivity. The goal of this study was to determine whether effector sensitivity could be used to enhance breeding for SNB resistance. We have demonstrated that SnTox1 effector sensitivity is common in current commercial Western Australian wheat cultivars. Thirty-three of 46 cultivars showed evidence of sensitivity to SnTox1. Of these, 19 showed moderate or strong chlorotic/necrotic responses to SnTox1. Thirteen were completely insensitive to SnTox1. Disease susceptibility was most closely associated with SnTox3 sensitivity. We have also identified biochemical evidence of a novel chlorosis-inducing protein or proteins in P. nodorum culture filtrates unmasked in strains that lack expression of ToxA, SnTox1 and SnTox3 activities.

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