The Biotrophic Fungus Cladosporium fulvum Circumvents Cf-4-Mediated Resistance by Producing Unstable AVR4 Elicitors

Joosten, M.H.A.J.; Vogelsang, R.; Cozijnsen, Ton J.; Verberne, Marianne C.; Wit, P.J.G.M. de

doi:10.2307/3870488

Cited by 44 publications

(103 citation statements)

References 19 publications

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“…Single cotyledons of 10-14-day-old-seedlings were inoculated with PVX::Avr4. MM-Cf0 tomato plants did not show a specific response upon systemic infection by PVX::Avr4, except for some mild mosaic virus symptoms at about 10 days after inoculation, similarly as described previously (Joosten et al, 1997). Tomato plants carrying the Cf-4 resistance locus showed necrotic spots on the cotyledons 3-4 days after inoculation.…”

Section: Characterization Of the Tagged Genementioning

confidence: 86%

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Identification and Ds‐tagged isolation of a new gene at the Cf‐4 locus of tomato involved in disease resistance to Cladosporium fulvum race 5

Takken¹,

Schipper²,

Nijkamp³

et al. 1998

The Plant Journal

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SummaryLeaf mould disease in tomato is caused by the biotrophic fungus Cladosporium fulvum. An Ac/Ds targeted transposon tagging strategy was used to isolate the gene conferring resistance to race 5 of C. fulvum, a strain expressing the avirulence gene Avr4. An infection assay of 2-weekold seedlings yielded five susceptible mutants, of which two had a Ds element integrated in the same gene at different positions. This gene, member of a gene family, showed high sequence homology to the C. fulvum resistance genes Cf-9 and Cf-2. The gene is predicted to encode an extracellular transmembrane protein containing a divided domain of 25 leucine-rich repeats. Three mutants exhibited a genomic deletion covering most of the Lycopersicon hirsutum introgressed segment, including the Cf-4 locus. Southern blot analysis revealed that this deletion includes the tagged gene and five homologous sequences. To test whether the tagged gene confers resistance to C. fulvum via Avr4 recognition, the Avr4 gene was expressed in planta. Surprisingly, expression of the Avr4 gene still triggered a specific necrotic response in the transposon-tagged plants, indicating that the tagged resistance gene is not, or is not the only gene, involved in Avr4 recognition. Mutants harbouring the genomic deletion did not show this Avr4-specific response. The deleted segment apparently contains, in addition to the tagged gene, one or more other genes, which play a role in the Avr4 responses. The tagged gene is present at the Cf-4 locus, but it does not necessarily recognize Avr4 and is therefore designated Cf-4A.

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Section: Characterization Of the Tagged Genementioning

confidence: 86%

“…The Avr4 protein was targeted to the apoplast by the PR-1A signal sequence of Nicotiana tabacum (Joosten et al, 1997), as in the PVX::Avr9 vector used by Hammond-Kosack et al (1995). Single cotyledons of 10-14-day-old-seedlings were inoculated with PVX::Avr4.…”

Section: Characterization Of the Tagged Genementioning

confidence: 99%

Identification and Ds‐tagged isolation of a new gene at the Cf‐4 locus of tomato involved in disease resistance to Cladosporium fulvum race 5

Takken¹,

Schipper²,

Nijkamp³

et al. 1998

The Plant Journal

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“…Previously we reported that Avr4 triggers a Cf-4-mediated HR (13). We examined whether MfAvr4, which is a functional chitin-binding lectin but shows only 42% identity to Avr4, also triggers a Cf-4-mediated HR.…”

Section: Fijiensis Avr4 Binds To Chitin and Protects Fungi Againstmentioning

confidence: 99%

Tomato Cf resistance proteins mediate recognition of cognate homologous effectors from fungi pathogenic on dicots and monocots

Stergiopoulos

Burg²,

Ökmen³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

172

212

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Most fungal effectors characterized so far are species-specific and facilitate virulence on a particular host plant. During infection of its host tomato, Cladosporium fulvum secretes effectors that function as virulence factors in the absence of cognate Cf resistance proteins and induce effector-triggered immunity in their presence. Here we show that homologs of the C. fulvum Avr4 and Ecp2 effectors are present in other pathogenic fungi of the Dothideomycete class, including Mycosphaerella fijiensis, the causal agent of black Sigatoka disease of banana. We demonstrate that the Avr4 homolog of M. fijiensis is a functional ortholog of C. fulvum Avr4 that protects fungal cell walls against hydrolysis by plant chitinases through binding to chitin and, despite the low overall sequence homology, triggers a Cf-4-mediated hypersensitive response (HR) in tomato. Furthermore, three homologs of C. fulvum Ecp2 are found in M. fijiensis, one of which induces different levels of necrosis or HR in tomato lines that lack or contain a putative cognate Cf-Ecp2 protein, respectively. In contrast to Avr4, which acts as a defensive virulence factor, M. fijiensis Ecp2 likely promotes virulence by interacting with a putative host target causing host cell necrosis, whereas Cf-Ecp2 could possibly guard the virulence target of Ecp2 and trigger a Cf-Ecp2-mediated HR. Overall our data suggest that Avr4 and Ecp2 represent core effectors that are collectively recognized by single cognate Cfproteins. Transfer of these Cf genes to plant species that are attacked by fungi containing these cognate core effectors provides unique ways for breeding disease-resistant crops.Cladosporium fulvum | Mycosphaerella fijiensis | effector-triggered immunity | biotrophy | toxigenic peptides

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“…Originally, AVR4 was identified as an extracellular race-specific elicitor of C. fulvum that induces plant defense responses in tomato plants carrying the comple-mentary Cf-4 resistance gene. Recognition of AVR4 is sufficient for induction of complete resistance in tomato against isolates of the fungus C. fulvum that carry the AVR4 encoding gene (13,14). The natural isolates of C. fulvum that were found to evade Cf-4-mediated resistance were reported to secrete proteasesensitive isoforms of AVR4, whereas native mature AVR4 (86 amino acids) is insensitive to these proteases (10,14).…”

mentioning

confidence: 99%

“…Recognition of AVR4 is sufficient for induction of complete resistance in tomato against isolates of the fungus C. fulvum that carry the AVR4 encoding gene (13,14). The natural isolates of C. fulvum that were found to evade Cf-4-mediated resistance were reported to secrete proteasesensitive isoforms of AVR4, whereas native mature AVR4 (86 amino acids) is insensitive to these proteases (10,14). The corresponding avr4 alleles in these isolates all contain single nucleotide polymorphisms causing in all but one case single amino acid substitutions (13).…”

mentioning

confidence: 99%

Binding of the AVR4 Elicitor of Cladosporium fulvum to Chitotriose Units Is Facilitated by Positive Allosteric Protein-Protein Interactions

Burg

Spronk

Boeren

et al. 2004

Journal of Biological Chemistry

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The attack of fungal cell walls by plant chitinases is an important plant defense response to fungal infection. Anti-fungal activity of plant chitinases is largely restricted to chitinases that contain a noncatalytic, plantspecific chitin-binding domain (ChBD) (also called Hevein domain). Current data confirm that the race-specific elicitor AVR4 of the tomato pathogen Cladosporium fulvum can protect fungi against plant chitinases, which is based on the presence of a novel type of ChBD in AVR4 that was first identified in invertebrates. Although these two classes of ChBDs (Hevein and invertebrate) are sequentially unrelated, they share structural homology. Here, we show that the chitin-binding sites of these two classes of ChBDs have different topologies and characteristics. The K D , ⌬H, and ⌬S values obtained for the interaction between AVR4 and chito-oligomers are comparable with those obtained for Hevein. However, the binding site of AVR4 is larger than that of Hevein, i.e. AVR4 interacts strictly with chitotriose, whereas Hevein can also interact with the monomer N-acetylglucosamine. Moreover, binding of additional AVR4 molecules to chitin occurs through positive cooperative protein-protein interactions. By this mechanism AVR4 is likely to effectively shield chitin on the fungal cell wall, preventing the cell wall from being degraded by plant chitinases.Binding and conversion of carbohydrates by proteins is of fundamental importance in numerous biological processes, including (self and nonself) cell-cell recognition, cell adhesion, and carbohydrate turnover. Recently, protein domains responsible for this interaction have been reclassified into distinct carbohydrate-binding modules (CBMs) 1 (1). CBMs are often present in carbohydrate-degrading enzymes, where they appear to mediate a prolonged and more intimate contact between the catalytic domain and insoluble carbohydrate polymers (2, 3). Lectins, on the other hand, are carbohydratebinding proteins that lack enzymatic activity but often contain tandem repeats of CBMs.Chitin, a polymer consisting of ␤-1,4-linked GlcNAc residues, is a major component of crustacean shells, insect exoskeletons, and fungal cell walls but is absent in plants. In higher organisms, two CBMs predominantly confer binding of proteins to chitin, i.e. the Hevein domain (hereafter denoted as CBM18) (4) and the invertebrate chitin-binding domain (CBM14) (5). CBM18 is nearly exclusively found in plants (to date one additional member of CBM18 has been identified in Streptomyces griseus; Ref. 6), whereas CBM14 is commonly found in the genomes of baculoviridae, invertebrates, and mammals but absent in plants (5). Both ChBDs are typical CBMs, i.e. lectins with tandem repeats are known for both (e.g. wheat germ agglutinin (WGA) (7) and peritrophin-44 (8)), and both domains can be found in chitinases. However, CBM18 is only fused to the plant-specific family 19 catalytic domain, whereas chitinases of mammals and invertebrates utilize CBM14 in combination with the family 18 catalytic domain. Seque...

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The Biotrophic Fungus Cladosporium fulvum Circumvents Cf-4-Mediated Resistance by Producing Unstable AVR4 Elicitors

Cited by 44 publications

References 19 publications

Identification and Ds‐tagged isolation of a new gene at the Cf‐4 locus of tomato involved in disease resistance to Cladosporium fulvum race 5

Identification and Ds‐tagged isolation of a new gene at the Cf‐4 locus of tomato involved in disease resistance to Cladosporium fulvum race 5

Tomato Cf resistance proteins mediate recognition of cognate homologous effectors from fungi pathogenic on dicots and monocots

Binding of the AVR4 Elicitor of Cladosporium fulvum to Chitotriose Units Is Facilitated by Positive Allosteric Protein-Protein Interactions

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