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

2014 ◽  
Vol 65 (2) ◽  
pp. 150 ◽  
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.

Prevalence and importance of sensitivity to the Stagonospora nodorum necrotrophic effector SnTox3 in current Western Australian wheat cultivars

2011 ◽  
Vol 62 (7) ◽  
pp. 556 ◽  
Author(s):  
Ormonde D. C. Waters ◽  
Judith Lichtenzveig ◽  
Kasia Rybak ◽  
Timothy L. Friesen ◽  
Richard P. Oliver
Keyword(s):  
Triticum Aestivum L ◽  
Stagonospora Nodorum ◽  
Similar Reaction ◽  
Wheat Cultivars ◽  
Australian Wheat ◽  
Necrotrophic Effector ◽  
Microbial Systems ◽  
Necrotrophic Effectors ◽  
Host Specific Toxins ◽  
Western Australian

Stagonospora nodorum is a major pathogen of wheat in many parts of the world and particularly in Western Australia. The pathosystem is characterised by interactions of multiple pathogen necrotrophic effectors (NE) (formerly host-specific toxins) with corresponding dominant host sensitivity loci. To date, five NE interactions have been reported in S. nodorum. Two proteinaceous NE (ToxA and SnTox3) have been cloned and expressed in microbial systems. The identification of wheat cultivars lacking sensitivity to one or more NE is a promising way to identify cultivars suitable for use in breeding for increased resistance to this economically important pathogen. The prevalence of sensitivity to the NE SnTox3 was investigated in 60 current Western Australian-adapted bread wheat (Triticum aestivum L.) cultivars. Infiltration of SnTox3 into seedling leaves caused a moderate or strong necrotic response in 52 cultivars. Six cultivars were insensitive and two cultivars exhibited a weak chlorotic response. Five of the cultivars that were insensitive or weakly sensitive to SnTox3 were noticeably more resistant to the disease. The 60 cultivars gave a very similar reaction to SnTox3 and to the crude S. nodorum SN15 culture filtrate demonstrating that SnTox3 is the dominant NE in this isolate. We conclude that a simple screen using both SnTox3 and ToxA effectors combined with simple greenhouse disease evaluation, will allow breeders to select cultivars that are more resistant to the disease, allowing them to concentrate resources on other still intractable breeding objectives.

scholarly journals Parastagonospora nodorum and Related Species in Western Canada: Genetic Variability and Effector Genes

2020 ◽  
Vol 110 (12) ◽  
pp. 1946-1958
Author(s):  
Mohamed Hafez ◽  
Ryan Gourlie ◽  
Therese Despins ◽  
Thomas K. Turkington ◽  
Timothy L. Friesen ◽  
...  
Keyword(s):  
Evolutionary Relationship ◽  
Haplotype Network ◽  
Bipolaris Sorokiniana ◽  
Western Canada ◽  
Pyrenophora Tritici Repentis ◽  
Septoria Nodorum Blotch ◽  
Effector Genes ◽  
Parastagonospora Nodorum ◽  
Almost All ◽  
Necrotrophic Effectors

Parastagonospora nodorum is an important fungal pathogen that causes Septoria nodorum blotch (SNB) in wheat. This pathogen produces several necrotrophic effectors that act as virulence factors; three have been cloned, SnToxA, SnTox1, and SnTox3. In this study, P. nodorum and its sister species P. avenaria f. tritici (Pat1) were isolated from wheat node and grain samples collected from distanced sites in western Canada during 2018. The presence of effector genes and associated haplotypes were determined by PCR and sequence analysis. An internal transcribed spacer-restriction fragment length polymorphism test was developed to distinguish between leaf spotting pathogens (P. nodorum, Pat1, Pyrenophora tritici-repentis, and Bipolaris sorokiniana). P. nodorum was mainly recovered from wheat nodes and to a lesser extent from the grains, while Pat1 was exclusively isolated from grain samples. The effector genes were present in almost all P. nodorum isolates, with the ToxA haplotype 5 (H5) being most prevalent, while a novel ToxA haplotype (denoted here H21) is reported for the first time. In Pat1, only combinations of SnTox1 and SnTox3 genes were present. A ToxA haplotype network was also constructed to assess the evolutionary relationship among globally found haplotypes to date. Finally, cultivars representing wheat development in Canada for the last century were tested for sensitivity to Sn-effectors and to the presence of Tsn1, the ToxA sensitivity gene. Of tested cultivars, 32.9 and 56.9% were sensitive to SnTox1 and SnTox3, respectively, and Tsn1 was present in 59% of the cultivars. In conclusion, P. nodorum and Pat1 were prevalent wheat pathogens in Canada with a potential tissue-specific colonization capacity, while producing necrotrophic effectors to which wheat is sensitive.

Understanding the plant-pathogen interaction associated with Septoria nodorum blotch of wheat

2021 ◽  
pp. 359-392
Author(s):  
Gayan K. Kariyawasam ◽  
◽  
Timothy L. Friesen ◽  
Keyword(s):  
Genome Sequencing ◽  
Genetic Relationship ◽  
Plant Pathogen ◽  
Gene Interactions ◽  
Septoria Nodorum ◽  
Septoria Nodorum Blotch ◽  
Plant Pathogen Interaction ◽  
Necrotrophic Effector ◽  
The Impact ◽  
Sensitivity Gene

This chapter discusses understanding the plant-pathogen interaction associated with septorium nodorum blotch of wheat. It begins by reviewing the necrotrophic effector-host sensitivity gene interactions in the wheat-P. nodorum system. It then reviews the genetic relationship between NE-sensitivity gene interactions and the importance of these interactions in the field. Additional QTL associated with susceptibility/resistance to P. nodorum is also discussed, followed by a section on the impact of genome sequencing in characterizing NE-sensitivity gene interactions.

scholarly journals New Insights into the Roles of Host Gene-Necrotrophic Effector Interactions in Governing Susceptibility of Durum Wheat to Tan Spot and Septoria nodorum Blotch

2016 ◽  
Vol 6 (12) ◽  
pp. 4139-4150 ◽  
Author(s):  
Simerjot K Virdi ◽  
Zhaohui Liu ◽  
Megan E Overlander ◽  
Zengcui Zhang ◽  
Steven S Xu ◽  
...  
Keyword(s):  
Durum Wheat ◽  
Common Wheat ◽  
Tan Spot ◽  
Septoria Nodorum ◽  
Pyrenophora Tritici Repentis ◽  
Septoria Nodorum Blotch ◽  
Necrotrophic Fungi ◽  
Host Genetic ◽  
Parastagonospora Nodorum ◽  
Necrotrophic Effector

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.

scholarly journals Identification and Characterization of the SnTox6-Snn6 Interaction in the Parastagonospora nodorum–Wheat Pathosystem

2015 ◽  
Vol 28 (5) ◽  
pp. 615-625 ◽  
Author(s):  
Y. Gao ◽  
J. D. Faris ◽  
Z. Liu ◽  
Y. M. Kim ◽  
R. A. Syme ◽  
...  
Keyword(s):  
Disease Development ◽  
Host Interaction ◽  
Septoria Nodorum Blotch ◽  
Polymerase Chain ◽  
Trait Locus ◽  
Parastagonospora Nodorum ◽  
Wheat Lines ◽  
Necrotrophic Effectors ◽  
Sensitivity Gene

Parastagonospora nodorum is a necrotrophic fungal pathogen that causes Septoria nodorum blotch (SNB) (formerly Stagonospora nodorum blotch) on wheat. P. nodorum produces necrotrophic effectors (NE) that are recognized by dominant host sensitivity gene products resulting in disease development. The NE–host interaction is critical to inducing NE-triggered susceptibility (NETS). To date, seven NE–host sensitivity gene interactions, following an inverse gene-for-gene model, have been identified in the P. nodorum–wheat pathosystem. Here, we used a wheat mapping population that segregated for sensitivity to two previously characterized interactions (SnTox1-Snn1 and SnTox3-Snn3-B1) to identify and characterize a new interaction involving the NE designated SnTox6 and the host sensitivity gene designated Snn6. SnTox6 is a small secreted protein that induces necrosis on wheat lines harboring Snn6. Sensitivity to SnTox6, conferred by Snn6, was light-dependent and was shown to underlie a major disease susceptibility quantitative trait locus (QTL). No other QTL were identified, even though the P. nodorum isolate used in this study harbored both the SnTox1 and SnTox3 genes. Reverse transcription-polymerase chain reaction showed that the expression of SnTox1 was not detectable, whereas SnTox3 was expressed and, yet, did not play a significant role in disease development. This work expands our knowledge of the wheat–P. nodorum interaction and further establishes this system as a model for necrotrophic specialist pathosystems.

Differential responses of Australian wheat cultivars to cadmium concentration in wheat grain

1995 ◽  
Vol 46 (5) ◽  
pp. 873 ◽  
Author(s):  
DP Oliver ◽  
JW Gartrell ◽  
KG Tiller ◽  
R Correll ◽  
GD Cozens ◽  
...  
Keyword(s):  
Selection Process ◽  
Cadmium Concentration ◽  
Wheat Variety ◽  
Wheat Cultivars ◽  
Wheat Grain ◽  
Cd Accumulation ◽  
Australian Wheat ◽  
Breeding Selection ◽  
A Site ◽  
Western Australian

Cadmium concentration in grain was studied for wheat cultivars grown nationally in the Interstate Wheat Variety (IWV) experiments (1988 and 1989) and cultivars grown in the Western Australian (WA) experiments (1990-1992). These experiments covered a range of differing soil and environmental conditions. The adaptation of these cultivars to changes in cadmium potential at a site was determined. Significant cultivar effects were identified, but these were less significant than the site effects. The Cd concentrations in grain exceeded the current Australian maximum permitted concentration (MPC) of 0.05 mg kg-1 at one site in the IWV experiments while the concentration exceeded the MPC at a larger proportion of sites in the WA experiments. Several trends in cultivar accumulation of Cd in grain were evident. Reeves and Kulin were found to have the highest Cd concentration at a number of sites for several years in both the IWV and WA experiments. The similar pedigrees of these two cultivars suggest that while wheat breeders were selecting for certain traits during the breeding selection process, they were inadvertently selecting for the ability to accumulate Cd. In the 1992 WA cultivar experiments, generally Aroona had the highest Cd concentration in grain. Aroona has different pedigree to Reeves and Kulin. Several of the cultivars that were low Cd accumulators also had similar pedigrees. This indicates that there is potential for selecting lines that are low Cd accumulators to be grown in areas where Cd accumulation in grain is a problem.

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

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.

scholarly journals Sensitivity genes in wheat and corresponding effector genes in necrotrophs exhibiting inverse gene-for-gene relationship

2021 ◽  
Author(s):  
Pushpendra Kumar Gupta ◽  
Neeraj Kumar Vasistha ◽  
Pawan Kumar Singh
Keyword(s):  
Bipolaris Sorokiniana ◽  
Relevant Information ◽  
Tan Spot ◽  
Future Research ◽  
Disease Symptoms ◽  
Septoria Nodorum Blotch ◽  
Effector Genes ◽  
Necrotrophic Effectors ◽  
S Genes ◽  
Gene For Gene

Abstract In wheat, genes for resistance (R) as well as susceptibility (S) are now known for several diseases. The S genes also include sensitivity genes like Tsn1 in wheat. R genes follow a gene-for-gene (GFG) relationship and generally involve biotrophs and S genes particularly sensitivity genes, follow an inverse gene-for-gene relationship (IGFG), generally involving necrotroph or hemi-biotroph pathogens. The toxin (virulence factor) genes of the pathogen and the corresponding sensitivity genes have been described in some detail for the following three pathogens: (i) Paratagonospora nodorum (causing Septoria nodorum blotch or SNB); (ii) Pyrenophora tritici-repentis (tan spot) and (iii) Bipolaris sorokiniana (spot blotch). These and some other pathogens produce several necrotrophic effectors (NEs), which interact directly or indirectly with the products of S genes in the host and produce disease symptoms like necrosis and/or chlorosis. In this article we present a critical review of all the relevant information about the interactions between NEs of the above three pathogens and the corresponding S genes in wheat. The gaps in knowledge and possibilities for future research are also discussed.

scholarly journals Variability in an effector gene promoter of a necrotrophic fungal pathogen dictates epistasis and effector-triggered susceptibility in wheat

2021 ◽  
Author(s):  
Evan John ◽  
Silke Jacques ◽  
Huyen Phan ◽  
Lifang Liu ◽  
Danilo Pereira ◽  
...  
Keyword(s):  
Regulatory Region ◽  
Gene Promoter ◽  
Epistatic Effect ◽  
Start Codon ◽  
Septoria Nodorum Blotch ◽  
Trait Locus ◽  
Repressor Molecule ◽  
Wheat Leaves ◽  
Parastagonospora Nodorum ◽  
Necrotrophic Effectors

The fungus Parastagonospora nodorum uses proteinaceous necrotrophic effectors (NEs) to induce tissue necrosis on wheat leaves during infection, leading to the symptoms of septoria nodorum blotch (SNB). The NEs Tox1 and Tox3 induce necrosis on wheat possessing the dominant susceptibility genes Snn1 and Snn3B1/Snn3D1, respectively. We previously observed that Tox1 is epistatic to the expression of Tox3 and a quantitative trait locus (QTL) on chromosome 2A that contributes to SNB resistance/susceptibility. The expression of Tox1 is significantly higher in the Australian strain SN15 compared to the American strain SN4. Inspection of the Tox1 promoter region revealed a 401 bp promoter genetic element in SN4 positioned 267 bp upstream of the start codon that is absent in SN15, called PE401. Analysis of the world-wide P. nodorum population revealed that a high proportion of Northern Hemisphere isolates possess PE401 whereas the opposite was observed in the Southern Hemisphere. The presence of PE401 ablates the epistatic effect of Tox1 on the contribution of the SNB 2A QTL but not Tox3. PE401 was introduced into the Tox1 promoter regulatory region in SN15 to test for direct regulatory roles. Tox1 expression was markedly reduced in the presence of PE401. This suggests a repressor molecule(s) binds PE401 and inhibits Tox1 transcription. Infection assays also demonstrated that P. nodorum which lacks PE401 is more pathogenic on Snn1 varieties than P. nodorum carrying PE401. An infection competition assay between P. nodorum isogenic strains with and without PE401 indicated that the higher Tox1-expressing strain rescued the reduced virulence of the lower Tox1-expressing strain on Snn1 wheat. Our study demonstrated that Tox1 exhibits both selfish and altruistic characteristics. This offers an insight into a NE arms race that is occurring within the P. nodorum population. The importance of PE401 in breeding for SNB resistance in wheat is discussed.

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

Plant Disease ◽  
2020 ◽  
Vol 104 (1) ◽  
pp. 71-81 ◽  
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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