The phytopathogenic fungus Alternaria brassicicola: Phytotoxin production and phytoalexin elicitation

Pedras, M. Soledade C.; Chumala, Paulos; Jin, Wei; Islam, Md. Sakinul; Hauck, Dominic

doi:10.1016/j.phytochem.2009.01.005

Cited by 106 publications

(119 citation statements)

References 35 publications

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“…Accordingly, germinating A. brassicicola conidia release a proteinaceous, host-specific AB toxin on leaves of host plants (Otani et al, 1998), and they also synthesize an array of potentially phytotoxic fusicoccane-like diterpenoids (MacKinnon et al, 1999). A recent systematic investigation of phytotoxic compounds produced by A. brassicicola revealed the presence of the host-specific toxin brassicicolin A and three mildly phytotoxic metabolites with fusicoccane structure in the culture broth of the fungus (Pedras et al, 2009). Cutinases and lipases secreted by A. brassicicola might contribute to the establishment of infection as well (Trail and Kö ller, 1993;Berto et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

Dual Roles of Reactive Oxygen Species and NADPH Oxidase RBOHD in an Arabidopsis-Alternaria Pathosystem

et al. 2009

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Arabidopsis (Arabidopsis thaliana) NADPH oxidases have been reported to suppress the spread of pathogen- and salicylic acid-induced cell death. Here, we present dual roles of RBOHD (for respiratory burst oxidase homolog D) in an Arabidopsis-Alternaria pathosystem, suggesting either initiation or prevention of cell death dependent on the distance from pathogen attack. Our data demonstrate that a rbohD knockout mutant exhibits increased spread of cell death at the macroscopic level upon inoculation with the fungus Alternaria brassicicola. However, the cellular patterns of reactive oxygen species accumulation and cell death are fundamentally different in the AtrbohD mutant compared with the wild type. Functional RBOHD causes marked extracellular hydrogen peroxide accumulation as well as cell death in distinct, single cells of A. brassicicola-infected wild-type plants. This single cell response is missing in the AtrbohD mutant, where infection triggers spreading-type necrosis preceded by less distinct chloroplastic hydrogen peroxide accumulation in large clusters of cells. While the salicylic acid analog benzothiadiazole induces the action of RBOHD and the development of cell death in infected tissues, the ethylene inhibitor aminoethoxyvinylglycine inhibits cell death, indicating that both salicylic acid and ethylene positively regulate RBOHD and cell death. Moreover, A. brassicicola-infected AtrbohD plants hyperaccumulate ethylene and free salicylic acid compared with the wild type, suggesting negative feedback regulation of salicylic acid and ethylene by RBOHD. We propose that functional RBOHD triggers death in cells that are damaged by fungal infection but simultaneously inhibits death in neighboring cells through the suppression of free salicylic acid and ethylene levels.

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Section: Discussionmentioning

confidence: 99%

Dual Roles of Reactive Oxygen Species and NADPH Oxidase RBOHD in an Arabidopsis-Alternaria Pathosystem

et al. 2009

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“…Germinating spores of A. brassicicola secrete the atypical host selective toxin (HST) AB toxin, which is a protein rather than a characteristic low molecular weight secondary metabolite (Otani et al, 1998). A. brassicicola produces Brassicicolin A as a major HST and mannitol derivatives that exhibit some degree of host toxicity (Pedras et al, 2009). Other secondary metabolites generated by this fungus include brassicicenes A-F, phomapyrone A/F/G, and infectopyrone though their exact roles in pathogenicity are yet to be determined (MacKinnon et al, 1999;Pedras et al, 2009).…”

Section: Examples Of Necrotrophic Infection Strategiesmentioning

confidence: 99%

“…A. brassicicola produces Brassicicolin A as a major HST and mannitol derivatives that exhibit some degree of host toxicity (Pedras et al, 2009). Other secondary metabolites generated by this fungus include brassicicenes A-F, phomapyrone A/F/G, and infectopyrone though their exact roles in pathogenicity are yet to be determined (MacKinnon et al, 1999;Pedras et al, 2009). A. brassicicola also produces the toxin depudecin, an inhibitor of histone deacetylases (Privalsky, 1998).…”

Section: Examples Of Necrotrophic Infection Strategiesmentioning

confidence: 99%

Necrotroph Attacks on Plants: Wanton Destruction or Covert Extortion?

Laluk

Mengiste

2010

The Arabidopsis Book

204

168

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Necrotrophic pathogens cause major pre-and post-harvest diseases in numerous agronomic and horticultural crops infl icting signifi cant economic losses. In contrast to biotrophs, obligate plant parasites that infect and feed on living cells, necrotrophs promote the destruction of host cells to feed on their contents. This difference underpins the divergent pathogenesis strategies and plant immune responses to biotrophic and necrotrophic infections. This chapter focuses on Arabidopsis immunity to necrotrophic pathogens. The strategies of infection, virulence and suppression of host defenses recruited by necrotrophs and the variation in host resistance mechanisms are highlighted. The multiplicity of intraspecifi c virulence factors and species diversity in necrotrophic organisms corresponds to variations in host resistance strategies. Resistance to host-specifi c necrotophs is monogenic whereas defense against broad host necrotrophs is complex, requiring the involvement of many genes and pathways for full resistance. Mechanisms and components of immunity such as the role of plant hormones, secondary metabolites, and pathogenesis-related proteins are presented. We will discuss the current state of knowledge of Arabidopsis immune responses to necrotrophic pathogens, the interactions of these responses with other defense pathways, and contemplate on the directions of future research.: e0136. of 34The Arabidopsis Book Infection by fungal necrotrophs generally involves stages of conidial attachment, germination, host penetration, primary lesion formation, lesion expansion, and tissue maceration followed by sporulation (Prins et al., 2000). Following germination, penetration may be achieved by active mechanisms such as appressoria formation and enzymatic degradation or passively through prior infection or wound sites as well as stomates (Prins et al., 2000). After entry, tissue is decomposed through further cellular dismantling using many of the lytic enzymes employed for initial penetration as well as toxic levels of reactive oxygen species (ROS). Many necrotrophs produce various low-molecular weight phytotoxic metabolites, ranging from host-specifi c to those having adverse effects on many diverse species (van Kan, 2006). Others secrete phytotoxic proteins known to induce necrosis, with the vast majority of broad host necrotrophs producing multiples of both (Pemberton and Salmond, 2004;Gijzen and Nurnberger, 2006;Choquer et al., 2007). Throughout infection, these fungi also actively manipulate host cellular machinery in order to suppress defenses and/or aid in disease progression. Some necrotrophs infl uence host phytohormone levels or employ their own hormone biosynthesis thereby disrupting defense signaling (Prins et al., 2000;Sharon et al., 2004). Others have adapted mechanisms to detoxify host metabolites that interfere with virulence (Morrissey and Osbourn, 1999).Overall, bacterial necrotrophs follow a similar mode of pathogenesis to their fungal counterparts, secreting virulence factors into host tissue to induc...

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“…This enzyme, originally named isonitrile hydratase (EC 4.2.1.103), was isolated from Pseudomonas putida strain N19-2 in a screen of soil-dwelling bacteria that could survive acclimatization to medium containing 0.02% (v/v) (ϳ1.6 mM) cyclohexyl isocyanide (8). The enzyme has subsequently been renamed cyclohexylisocyanide hydratase (ICH) 5 and is a 48-kDa homodimeric protein that catalyzes the addition of water to the isocyano group of various organic isocyanides to yield the corresponding N-formamide (Fig. 1B).…”

mentioning

confidence: 99%

Evolution of New Enzymatic Function by Structural Modulation of Cysteine Reactivity in Pseudomonas fluorescens Isocyanide Hydratase

Lakshminarasimhan¹,

Madzelan²,

Nan³

et al. 2010

Journal of Biological Chemistry

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Isocyanide (formerly isonitrile) hydratase (EC 4.2.1.103) is an enzyme of the DJ-1 superfamily that hydrates isocyanides to yield the corresponding N-formamide. In order to understand the structural basis for isocyanide hydratase (ICH) catalysis, we determined the crystal structures of wild-type and several sitedirected mutants of Pseudomonas fluorescens ICH at resolutions ranging from 1.0 to 1.9 Å . We also developed a simple UV-visible spectrophotometric assay for ICH activity using 2-naphthyl isocyanide as a substrate. ICH contains a highly conserved cysteine residue (Cys 101 ) that is required for catalysis and interacts with Asp 17 , Thr 102 , and an ordered water molecule in the active site. Asp 17 has carboxylic acid bond lengths that are consistent with protonation, and we propose that it activates the ordered water molecule to hydrate organic isocyanides. In contrast to Cys 101 and Asp 17 , Thr 102 is tolerant of mutagenesis, and the T102V mutation results in a substrate-inhibited enzyme. Although ICH is similar to human DJ-1 (1.6 Å C-␣ root mean square deviation), structural differences in the vicinity of Cys 101 disfavor the facile oxidation of this residue that is functionally important in human DJ-1 but would be detrimental to ICH activity. The ICH active site region also exhibits surprising conformational plasticity and samples two distinct conformations in the crystal. ICH represents a previously uncharacterized clade of the DJ-1 superfamily that possesses a novel enzymatic activity, demonstrating that the DJ-1 core fold can evolve diverse functions by subtle modulation of the environment of a conserved, reactive cysteine residue.

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The phytopathogenic fungus Alternaria brassicicola: Phytotoxin production and phytoalexin elicitation

Cited by 106 publications

References 35 publications

Dual Roles of Reactive Oxygen Species and NADPH Oxidase RBOHD in an Arabidopsis-Alternaria Pathosystem

Dual Roles of Reactive Oxygen Species and NADPH Oxidase RBOHD in an Arabidopsis-Alternaria Pathosystem

Necrotroph Attacks on Plants: Wanton Destruction or Covert Extortion?

Evolution of New Enzymatic Function by Structural Modulation of Cysteine Reactivity in Pseudomonas fluorescens Isocyanide Hydratase

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