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PMID: 17565943 Published · ppublish English Journal Article Research Support, U.S. Gov't, Non-P.H.S.

Silencing of the aflatoxin gene cluster in a diploid strain of Aspergillus flavus is suppressed by ectopic aflR expression.

Genetics ·Vol. 176 ·No. 4 ·2007-08-00 ·Pages 2077-86

Smith CA, Woloshuk CP, Robertson D, Payne GA

Abstract

Aflatoxins are toxic secondary metabolites produced by a 70-kb cluster of genes in Aspergillus flavus. The cluster genes are coordinately regulated and reside as a single copy within the genome. Diploids between a wild-type strain and a mutant (649) lacking the aflatoxin gene cluster fail to produce aflatoxin or transcripts of the aflatoxin pathway genes. This dominant phenotype is rescued in diploids between a wild-type strain and a transformant of the mutant containing an ectopic copy of aflR, the transcriptional regulator of the aflatoxin biosynthetic gene cluster. Further characterization of the mutant showed that it is missing 317 kb of chromosome III, including the known genes for aflatoxin biosynthesis. In addition, 939 kb of chromosome II is present as a duplication on chromosome III in the region previously containing the aflatoxin gene cluster. The lack of aflatoxin production in the diploid was not due to a unique or a mis-expressed repressor of aflR. Instead a form of reversible silencing based on the position of aflR is likely preventing the aflatoxin genes from being expressed in 649 x wild-type diploids. Gene expression analysis revealed the silencing effect is specific to the aflatoxin gene cluster.

MeSH Terms
Aflatoxins/genetics Aspergillus flavus/genetics Base Sequence DNA Primers/genetics DNA, Fungal/genetics DNA-Binding Proteins/genetics Diploidy Fungal Proteins/genetics Gene Dosage Gene Expression Gene Silencing Genes, Fungal Multigene Family Mutation Sequence Deletion Transcription Factors/genetics Transformation, Genetic
Chemicals
AFLR protein, Aspergillus Aflatoxins DNA Primers DNA, Fungal DNA-Binding Proteins Fungal Proteins Transcription Factors
Authors & Affiliations
4 authors, click to expand affiliations / ORCID
Smith Carrie A
Department of Genetics, North Carolina State University, Raleigh, NC 27695, USA.
Woloshuk Charles P
Robertson Dominique
Payne Gary A
References (47)
47 references, click to expand
  1. Cloning and characterization of the O-methyltransferase I gene (dmtA) from Aspergillus parasiticus associated with the conversions of demethylsterigmatocystin to sterigmatocystin and dihydrodemethylsterigmatocystin to dihydrosterigmatocystin in aflatoxin biosynthesis.
    Appl Environ Microbiol. 1999 Nov;65(11):4987-94 PMID: 10543813
  2. Cloning and characterization of avfA and omtB genes involved in aflatoxin biosynthesis in three Aspergillus species.
    Gene. 2000 May 2;248(1-2):157-67 PMID: 10806361
  3. adhA in Aspergillus parasiticus is involved in conversion of 5'-hydroxyaverantin to averufin.
    Appl Environ Microbiol. 2000 Nov;66(11):4715-9 PMID: 11055914
  4. Genetics of Aspergillus flavus: complementation and mapping of aflatoxin mutants.
    Genet Res. 1979 Aug;34(1):1-9 PMID: 116906
  5. Meiotic silencing by unpaired DNA.
    Cell. 2001 Dec 28;107(7):905-16 PMID: 11779466
  6. Quelling in Neurospora crassa.
    Adv Genet. 2002;46:277-303 PMID: 11931228
  7. Involvement of small RNAs and role of the qde genes in the gene silencing pathway in Neurospora.
    Genes Dev. 2002 Apr 1;16(7):790-5 PMID: 11937487
  8. A cytosine methyltransferase homologue is essential for repeat-induced point mutation in Neurospora crassa.
    Proc Natl Acad Sci U S A. 2002 Jun 25;99(13):8802-7 PMID: 12072568
  9. The genome sequence of the filamentous fungus Neurospora crassa.
    Nature. 2003 Apr 24;422(6934):859-68 PMID: 12712197
  10. Cloning and functional expression of an esterase gene in Aspergillus parasitcus.
    Mycopathologia. 2002;156(3):227-34 PMID: 12749588
  11. Mycotoxins.
    Clin Microbiol Rev. 2003 Jul;16(3):497-516 PMID: 12857779
  12. Isolation and characterization of a gene from Aspergillus parasiticus associated with the conversion of versicolorin A to sterigmatocystin in aflatoxin biosynthesis.
    Appl Environ Microbiol. 1992 Nov;58(11):3527-37 PMID: 1339261
  13. Clustered pathway genes in aflatoxin biosynthesis.
    Appl Environ Microbiol. 2004 Mar;70(3):1253-62 PMID: 15006741
  14. LaeA, a regulator of secondary metabolism in Aspergillus spp.
    Eukaryot Cell. 2004 Apr;3(2):527-35 PMID: 15075281
  15. Cloning of a gene associated with aflatoxin B1 biosynthesis in Aspergillus parasiticus.
    Curr Genet. 1992 Mar;21(3):231-3 PMID: 1563048
  16. RNA silencing of mycotoxin production in Aspergillus and Fusarium species.
    Mol Plant Microbe Interact. 2005 Jun;18(6):539-45 PMID: 15986923
  17. Regulation of secondary metabolism in filamentous fungi.
    Annu Rev Phytopathol. 2005;43:437-58 PMID: 16078891
  18. Sequence breakpoints in the aflatoxin biosynthesis gene cluster and flanking regions in nonaflatoxigenic Aspergillus flavus isolates.
    Fungal Genet Biol. 2005 Nov;42(11):914-23 PMID: 16154781
  19. Fungal secondary metabolism - from biochemistry to genomics.
    Nat Rev Microbiol. 2005 Dec;3(12):937-47 PMID: 16322742
  20. Secondary metabolic gene cluster silencing in Aspergillus nidulans.
    Mol Microbiol. 2006 Sep;61(6):1636-45 PMID: 16968230
  21. Amy1, the alpha-Amylase Gene of Aspergillus flavus: Involvement in Aflatoxin Biosynthesis in Maize Kernels.
    Phytopathology. 1999 Oct;89(10):908-14 PMID: 18944734
  22. Trans-sensing effects from Drosophila to humans.
    Cell. 1991 Apr 19;65(2):201-3 PMID: 2015622
  23. Premeiotic instability of repeated sequences in Neurospora crassa.
    Annu Rev Genet. 1990;24:579-613 PMID: 2150906
  24. Genetic transformation system for the aflatoxin-producing fungus Aspergillus flavus.
    Appl Environ Microbiol. 1989 Jan;55(1):86-90 PMID: 2495764
  25. Whole genome comparison of Aspergillus flavus and A. oryzae.
    Med Mycol. 2006 Sep 1;44(Supplement_1):S9-S11 PMID: 30408940
  26. Improved method of screening for aflatoxin with a coconut agar medium.
    Appl Environ Microbiol. 1987 Jul;53(7):1593-5 PMID: 3116928
  27. GUS fusions: beta-glucuronidase as a sensitive and versatile gene fusion marker in higher plants.
    EMBO J. 1987 Dec 20;6(13):3901-7 PMID: 3327686
  28. The parasexual cycle in Aspergillus flavus.
    Mycologia. 1973 Sep-Oct;65(5):1201-5 PMID: 4201875
  29. Aflatoxins in mutants of Aspergillus flavus.
    Mycopathol Mycol Appl. 1974 Apr 30;52(3):223-9 PMID: 4210373
  30. Genetics of Aspergillus flavus: linkage of aflatoxin mutants.
    Can J Microbiol. 1984 Jan;30(1):68-73 PMID: 6424919
  31. Molecular characterization of the afl-1 locus in Aspergillus flavus.
    Appl Environ Microbiol. 1995 Aug;61(8):3019-23 PMID: 7487033
  32. The Aspergillus parasiticus polyketide synthase gene pksA, a homolog of Aspergillus nidulans wA, is required for aflatoxin B1 biosynthesis.
    Mol Gen Genet. 1995 Aug 21;248(3):270-7 PMID: 7565588
  33. A beta-glucuronidase reporter gene construct for monitoring aflatoxin biosynthesis in Aspergillus flavus.
    Appl Environ Microbiol. 1995 Jul;61(7):2482-6 PMID: 7618859
  34. Molecular characterization of aflR, a regulatory locus for aflatoxin biosynthesis.
    Appl Environ Microbiol. 1994 Jul;60(7):2408-14 PMID: 8074521
  35. Cloning and characterization of a cDNA from Aspergillus parasiticus encoding an O-methyltransferase involved in aflatoxin biosynthesis.
    Appl Environ Microbiol. 1993 Nov;59(11):3564-71 PMID: 8285664
  36. Cloning of the afl-2 gene involved in aflatoxin biosynthesis from Aspergillus flavus.
    Appl Environ Microbiol. 1993 Jan;59(1):156-62 PMID: 8439147
  37. Structure and function of fas-1A, a gene encoding a putative fatty acid synthetase directly involved in aflatoxin biosynthesis in Aspergillus parasiticus.
    Appl Environ Microbiol. 1996 Jan;62(1):191-5 PMID: 8572694
  38. Isolation and characterization of the versicolorin B synthase gene from Aspergillus parasiticus. Expansion of the aflatoxin b1 biosynthetic gene cluster.
    J Biol Chem. 1996 Jun 7;271(23):13600-8 PMID: 8662689
  39. Meiotic transvection in fungi.
    Cell. 1996 Jul 12;86(1):103-13 PMID: 8689677
  40. Purification and characterization of versicolorin B synthase from Aspergillus parasiticus. Catalysis of the stereodifferentiating cyclization in aflatoxin biosynthesis essential to DNA interaction.
    Biochemistry. 1996 Sep 3;35(35):11470-86 PMID: 8784203
  41. Identification of aflatoxin biosynthesis genes by genetic complementation in an Aspergillus flavus mutant lacking the aflatoxin gene cluster.
    Appl Environ Microbiol. 1996 Oct;62(10):3567-71 PMID: 8967772
  42. Heterologous expression, isolation, and characterization of versicolorin B synthase from Aspergillus parasiticus. A key enzyme in the aflatoxin B1 biosynthetic pathway.
    J Biol Chem. 1997 Jan 10;272(2):804-13 PMID: 8995367
  43. Aspergillus nidulans stcL encodes a putative cytochrome P-450 monooxygenase required for bisfuran desaturation during aflatoxin/sterigmatocystin biosynthesis.
    J Biol Chem. 1997 Jan 17;272(3):1589-94 PMID: 8999832
  44. avnA, a gene encoding a cytochrome P-450 monooxygenase, is involved in the conversion of averantin to averufin in aflatoxin biosynthesis in Aspergillus parasiticus.
    Appl Environ Microbiol. 1997 Apr;63(4):1349-56 PMID: 9097431
  45. DNA methylation inhibits elongation but not initiation of transcription in Neurospora crassa.
    Genes Dev. 1997 Sep 15;11(18):2383-95 PMID: 9308966
  46. Characterization of aflJ, a gene required for conversion of pathway intermediates to aflatoxin.
    Appl Environ Microbiol. 1998 Oct;64(10):3713-7 PMID: 9758789
  47. Characterization of the critical amino acids of an Aspergillus parasiticus cytochrome P-450 monooxygenase encoded by ordA that is involved in the biosynthesis of aflatoxins B1, G1, B2, and G2.
    Appl Environ Microbiol. 1998 Dec;64(12):4834-41 PMID: 9835571
Article Info
Journal
Genetics
Abbr.
Genetics
ISSN
0016-6731
DOI
10.1534/genetics.107.073460
Published
2007-08-00
Epub
2007-00-11
Pages
2077-86
Language
English
Region
United States
NLM ID
0374636
PMCID
PMC1950615
Subset
IM
External Links
PubMed source DOI: 10.1534/genetics.107.073460 PMC Full Text View journal details
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