Northern Corn Leaf Spot: Chemistry, Enzymology, and Molecular Genetics of a Host-Selective Phytotoxin

Walton, Jonathan D.; Ransom, Richard F.; Pitkin, John W.

doi:10.1007/978-1-4615-6019-7_5

Cited by 9 publications

(13 citation statements)

References 98 publications

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“…The disease emerged in the first half of the 20th century and HC-toxin isolated from Cochliobolus carbonum was identified as a major determinant of host specificity and virulence in the 1960s. HC-toxin is only produced by race 1 isolates of the fungus, which generally cause larger lesions on susceptible maize cultivars compared with the HC-toxin-deficient races 2 and 3 (Walton et al, 1997). HC-toxin is an important virulence factor and a major determinant of the disease on maize.…”

Section: Sm Hsts Produced By Dothideomycetesmentioning

confidence: 99%

Phytotoxic secondary metabolites and peptides produced by plant pathogenicDothideomycetefungi

Stergiopoulos¹,

Collemare²,

Mehrabi³

et al. 2013

FEMS Microbiol Rev

164

103

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Many necrotrophic plant pathogenic fungi belonging to the class of Dothideomycetes produce phytotoxic metabolites and peptides that are usually required for pathogenicity. Phytotoxins that affect a broad range of plant species are known as non-host-specific toxins (non-HSTs), whereas HSTs affect only a particular plant species or more often genotypes of that species. For pathogens producing HSTs, pathogenicity and host specificity are largely defined by the ability to produce the toxin, while plant susceptibility is dependent on the presence of the toxin target. Non-HSTs are not the main determinants of pathogenicity but contribute to virulence of the producing pathogen. Dothideomycetes are remarkable for the production of toxins, particularly HSTs because they are the only fungal species known so far to produce them. The synthesis, regulation, and mechanisms of action of the most important HSTs and non-HSTs will be discussed. Studies on the mode of action of HSTs have highlighted the induction of programed cell death (PCD) as an important mechanism. We discuss HST-induced PCD and the plant hypersensitive response upon recognition of avirulence factors that share common pathways. In this respect, although nucleotide-binding-site-leucine-rich repeat types of resistance proteins mediate resistance against biotrophs, they can also contribute to susceptibility toward necrotrophs.

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Section: Sm Hsts Produced By Dothideomycetesmentioning

confidence: 99%

Phytotoxic secondary metabolites and peptides produced by plant pathogenicDothideomycetefungi

Stergiopoulos¹,

Collemare²,

Mehrabi³

et al. 2013

FEMS Microbiol Rev

164

103

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“…HC-toxin, a cyclic tetrapeptide, is a determinant of virulence and host specificity in the interaction between the producing fungus, Cochliobolus carbonum, and its host, maize (49). HCtoxin biosynthesis is controlled by a single Mendelian locus called TOX2.…”

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confidence: 99%

Characterization of Inhibitor-Resistant Histone Deacetylase Activity in Plant-Pathogenic Fungi

et al. 2002

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HC-toxin, a cyclic peptide made by the filamentous fungus Cochliobolus carbonum, is an inhibitor of histone deacetylase (HDAC) from many organisms. It was shown earlier that the HDAC activity in crude extracts of C. carbonum is relatively insensitive to HC-toxin as well as to the chemically unrelated HDAC inhibitors trichostatin and D85, whereas the HDAC activity of Aspergillus nidulans is sensitive (G. Brosch et al., Biochemistry 40:12855-12863, 2001). Here we report that HC-toxin-resistant HDAC activity was present in other, but not all, plant-pathogenic Cochliobolus species but not in any of the saprophytic species tested. The HDAC activities of the fungi Alternaria brassicicola and Diheterospora chlamydosporia, which also make HDAC inhibitors, were resistant. The HDAC activities of all C. carbonum isolates tested, except one non-toxin-producing isolate, were resistant. In a cross between a sensitive isolate and a resistant isolate, resistance genetically cosegregated with HC-toxin production. When fractionated by anion-exchange chromatography, extracts of resistant and sensitive isolates and species had two peaks of HDAC activity, one that was fully HC-toxin resistant and a second that was larger and sensitive. The first peak was consistently smaller in extracts of sensitive fungi than in resistant fungi, but the difference appeared to be insufficiently large to explain the differential sensitivities of the crude extracts. Differences in mRNA expression levels of the four known HDAC genes of C. carbonum did not account for the observed differences in HDAC activity profiles. When mixed together, resistant extracts protected extracts of sensitive C. carbonum but did not protect other sensitive Cochlibolus species or Neurospora crassa. Production of this extrinsic protection factor was dependent on TOXE, the transcription factor that regulates the HC-toxin biosynthetic genes. The results suggest that C. carbonum has multiple mechanisms of self-protection against HC-toxin.

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“…C. carbonum (imperfect stage Helminthosporium carbonum or Bipolaris zeicola) causes leaf spot and ear rot of maize plants that are homozygous recessive at the Hm locus, whereas maize that is heterozygous or homozygous dominant at Hm is 100-fold less sensitive to HC toxin and develops only small, nonexpanding lesions when infected with Tox2+ isolates [151,152]. The production of HC toxin [structure cyclo-(D-proline-L-alanine-D-alanine-L-Aeo)] is under the control of TOX2, a complex genetic locus that consists of at least three different duplicated genes that are unique to Tox2+ isolates [151], encoding a 570-kDa tetrapartite cyclic peptide synthetase [153], a putative membrane antibiotic efflux pump encoded by TOXA and a gene called TOXC that encodes a putative Aeo synthase [154]. The demonstration that HC toxin inhibits partially purified 714 S. Graessle et al Histone acetylation: plants and fungi as model systems for the investigation of histone deacetylases HD1-A, HD1-B and HD2 of maize, but also HDACs of chicken and the myxomycete P. polycephalum led to the hypothesis that HDAC is the biologically significant site of action of HC toxin [28].…”

Section: Hc Toxin and Chlamydocinmentioning

confidence: 99%

Histone acetylation: plants and fungi as model systems for the investigation of histone deacetylases

Graessle¹,

Loidl²,

Brosch³

2001

CMLS, Cell. Mol. Life Sci.

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The basic element of chromatin is the nucleosome. Histones H4, H3, H2A and H2B form the core histone octamer by protein-protein interactions of their folded domains. The free, flexible N-terminal extensions of the histones protrude from the nuclesome; they contain conserved lysines undergoing posttranslational acetylation. Histone acetyltransferases (HATs) transfer the acetyl moiety of acetyl-coenzyme A to the epsilon-amino group; this reaction is reverted by histone deacetylases (HDACs). The dynamic equilibrium of the acetylation/deacetylation reaction varies throughout the genome; some regions in chromatin undergo rapid acetylation/deacetylation, whereas others are fixed in a certain acetylation state without significant changes. In general, chromatin regions engaged in transcription display dynamic acetylation, i.e. HATs and HDACs are recruited to these regions. Higher plants and fungi have considerably contributed to the unraveling of the multiplicity of HDACs; in particular, plants possess HDACs that have so far not been identified in animal cells.

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Northern Corn Leaf Spot: Chemistry, Enzymology, and Molecular Genetics of a Host-Selective Phytotoxin

Cited by 9 publications

References 98 publications

Phytotoxic secondary metabolites and peptides produced by plant pathogenicDothideomycetefungi

Phytotoxic secondary metabolites and peptides produced by plant pathogenicDothideomycetefungi

Characterization of Inhibitor-Resistant Histone Deacetylase Activity in Plant-Pathogenic Fungi

Histone acetylation: plants and fungi as model systems for the investigation of histone deacetylases

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