Functional Analyses of the Diels-Alderase Gene sol5 of Ascochyta rabiei and Alternaria solani Indicate that the Solanapyrone Phytotoxins Are Not Required for Pathogenicity

Kim, Wonyong; Park, Chung‐Min; Park, Jeong Jin; Akamatsu, Hajime; Peever, Tobin L.; Xian, Ming; Gang, David R.; Vandemark, George J.; Chen, Weidong

doi:10.1094/mpmi-08-14-0234-r

Cited by 31 publications

(55 citation statements)

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“…However, a recent functional study showed that solanapyrones are not required for A. rabiei and Al. solani to cause disease in the host plants (27).The genomes of filamentous fungi are larger and more complex than the genomes of prokaryotes because of the presence of AT-rich regions containing large noncoding regions and degenerated genes (i.e., pseudogenes). These AT-rich regions are also rich in transposable elements (TEs) and repetitive DNA sequences, which scatter along the genome and alternate with large GC-equilibrated regions in which most of the predicted genes reside (28).…”

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“…However, a recent functional study showed that solanapyrones are not required for A. rabiei and Al. solani to cause disease in the host plants (27).…”

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“…Recently, genetic evidence that the sol5 gene, encoding a Diels-Alderase, catalyzes the final step of solanapyrone biosynthesis both in A. rabiei and in Al. solani was obtained (27). The sol3 gene (encoding a dehydrogenase) was proposed to convert solanapyrone A to a less phytotoxic metabolite, solanapyrone B (22,25).…”

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“…The sol3 gene (encoding a dehydrogenase) was proposed to convert solanapyrone A to a less phytotoxic metabolite, solanapyrone B (22,25). However, some studies showed that solanapyrone B is not detectable in culture filtrates of A. rabiei, and the role of the sol3 gene in solanapyrone metabolism remains to be elucidated (17,27).…”

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“…The solanapyrone gene clusters in A. rabiei and Al. solani are known to contain a transcription factor (TF; encoded by sol4) similar to the fungus-specific Zn(II)2Cys6 zinc cluster transcription factor (C 6 zinc cluster TF) family (22,27). The C 6 zinc cluster TF family represents one of the largest classes of transcriptional regulators in fungi, as exemplified by Gal4 from the yeast Saccharomyces cerevisiae (42).…”

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A Novel Type Pathway-Specific Regulator and Dynamic Genome Environments of a Solanapyrone Biosynthesis Gene Cluster in the Fungus Ascochyta rabiei

et al. 2015

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c Secondary metabolite genes are often clustered together and situated in particular genomic regions, like the subtelomere, that can facilitate niche adaptation in fungi. Solanapyrones are toxic secondary metabolites produced by fungi occupying different ecological niches. Full-genome sequencing of the ascomycete Ascochyta rabiei revealed a solanapyrone biosynthesis gene cluster embedded in an AT-rich region proximal to a telomere end and surrounded by Tc1/Mariner-type transposable elements. The highly AT-rich environment of the solanapyrone cluster is likely the product of repeat-induced point mutations. Several secondary metabolism-related genes were found in the flanking regions of the solanapyrone cluster. Although the solanapyrone cluster appears to be resistant to repeat-induced point mutations, a P450 monooxygenase gene adjacent to the cluster has been degraded by such mutations. Among the six solanapyrone cluster genes (sol1 to sol6), sol4 encodes a novel type of Zn(II)2Cys6 zinc cluster transcription factor. Deletion of sol4 resulted in the complete loss of solanapyrone production but did not compromise growth, sporulation, or virulence. Gene expression studies with the sol4 deletion and sol4-overexpressing mutants delimited the boundaries of the solanapyrone gene cluster and revealed that sol4 is likely a specific regulator of solanapyrone biosynthesis and appears to be necessary and sufficient for induction of the solanapyrone cluster genes. Despite the dynamic surrounding genomic regions, the solanapyrone gene cluster has maintained its integrity, suggesting important roles of solanapyrones in fungal biology.T he subtelomere, the region upstream of the telomere on a linear chromosome, is characterized by richness in repetitive sequences and frequent chromosomal rearrangement and lacks synteny among closely related species and even within the same species in fungi (1-4). Subtelomeric regions are also enriched with duplicate, translocated, and horizontally transferred genes and thought to be evolutionarily labile and important for niche adaptation (2, 5, 6). These plastic chromosomal regions often include contingency genes, such as genes involved in membrane transport (2, 6), nutrient assimilation (2, 7), anaerobiosis (8), and virulence (1, 9, 10). Secondary metabolite (SM) gene clusters also exhibit a subtelomeric bias (11)(12)(13)(14).In fungi, SMs play diverse roles in host and niche specialization, serving as virulence factors, antibiotics, and metal ionchelating agents (15, 16). Solanapyrones are polyketide-derived SMs that were originally found in the plant-pathogenic fungi Alternaria solani and Ascochyta rabiei (17, 18), as well as in some other ascomycetous fungi occupying different ecological niches (19-21). The fact that solanapyrones are produced by distantly related species like Nigrospora (Sordariomycetes) but not by closely related species of Ascochyta or Alternaria (Dothideomycetes) suggests the acquisition of the entire gene cluster by horizontal gene transfer (HGT) events. Recently, th...

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“…However, a recent functional study showed that solanapyrones are not required for A. rabiei and Al. solani to cause disease in the host plants (27).…”

mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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A Novel Type Pathway-Specific Regulator and Dynamic Genome Environments of a Solanapyrone Biosynthesis Gene Cluster in the Fungus Ascochyta rabiei

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Enzymkaskadenreaktionen in der Biosynthese

Walsh

Moore

2019

Angewandte Chemie

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Enzym‐vermittelte Kaskadenreaktionen sind weit verbreitet. Um einen Vergleich mit den mechanistischen Kategorisierungen der komplementären Kaskadenreaktionen in der organischen Synthese zu ermöglichen sowie um die gemeinsamen Grundlagen aufzuzeigen, erörtern wir hier vier Arten von Enzymkaskadenreaktionen: vermittelt durch nucleophile, elektrophile, pericyclische und radikalische Reaktionen. Zwei Subtypen von Enzymen, die radikalische Kaskaden erzeugen, befinden sich an den entgegengesetzten Enden der Abundanzskala von Sauerstoff: Eisen‐basierte Enzyme nutzen O2, um hochvalente Eisen‐Oxo‐Spezies zu erzeugen, die nichtaktivierte C‐H‐Bindungen in Substraten homolytisch spalten und Gerüstumlagerungen einleiten. Am anaeroben Ende spalten Enzyme reversibel S‐Adenosylmethionin (SAM) unter Bildung des 5′‐Desoxyadenosyl‐Radikals als starkes Oxidans, um die homolytische Spaltung von C‐H‐Bindungen in gebundenen Substraten auszulösen. Die letztgenannten Enzyme werden als Radikal‐SAM‐Enzyme bezeichnet. Die erstgenannten Enzyme kategorisieren wir als “verhinderte Oxygenasen”.

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Enzymatic Cascade Reactions in Biosynthesis

2019

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Cascade reactions in organic synthesis, especially in natural product campaigns with biomimetic strategies, have previously been reviewed. Here we take up the complementary topic of enzyme-mediated cascade reactions and note their widespread occurrence. To facilitate comparison with the mechanistic categorizations of cascade reactions by synthetic chemists and delineate the common underlying chemistry, we discuss four types of enzymatic cascade reactions: those mediated by nucleophilic, electrophilic, pericyclic, and radical-based chemistries. Two subtypes of enzyme generating radical cascades exist at opposite ends of the oxygen abundance spectrum. Iron-based enzymes use O2 to generate high valent iron-oxo species to homolyze unactivated C-H bonds in substrates that set off skeletal rearrangements. At the anaerobic end, enzymes reversibly cleave S-adenosylmethionine (SAM) to generate the 5'-deoxyadenosyl radical as a powerful oxidant to initiate C-H bond homolysis in bound substrates. The latter enzymes are termed radical SAM enzymes. We categorize the former as "thwarted oxygenases".

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Functional Analyses of the Diels-Alderase Gene sol5 of Ascochyta rabiei and Alternaria solani Indicate that the Solanapyrone Phytotoxins Are Not Required for Pathogenicity

Cited by 31 publications

References 73 publications

A Novel Type Pathway-Specific Regulator and Dynamic Genome Environments of a Solanapyrone Biosynthesis Gene Cluster in the Fungus Ascochyta rabiei

A Novel Type Pathway-Specific Regulator and Dynamic Genome Environments of a Solanapyrone Biosynthesis Gene Cluster in the Fungus Ascochyta rabiei

Enzymkaskadenreaktionen in der Biosynthese

Enzymatic Cascade Reactions in Biosynthesis

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