• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of geneticsGeneticsCurrent IssueInformation for AuthorsEditorial BoardSubscribeSubmit a Manuscript
Genetics. May 2002; 161(1): 59–70.
PMCID: PMC1462115

A conditionally dispensable chromosome controls host-specific pathogenicity in the fungal plant pathogen Alternaria alternata.


The filamentous fungus Alternaria alternata contains seven pathogenic variants (pathotypes), which produce host-specific toxins and cause diseases on different plants. Previously, the gene cluster involved in host-specific AK-toxin biosynthesis of the Japanese pear pathotype was isolated, and four genes, named AKT genes, were identified. The AKT homologs were also found in the strawberry and tangerine pathotypes, which produce AF-toxin and ACT-toxin, respectively. This result is consistent with the fact that the toxins of these pathotypes share a common 9,10-epoxy-8-hydroxy-9-methyl-decatrienoic acid structural moiety. In this study, three of the AKT homologs (AFT1-1, AFTR-1, and AFT3-1) were isolated on a single cosmid clone from strain NAF8 of the strawberry pathotype. In NAF8, all of the AKT homologs were present in multiple copies on a 1.05-Mb chromosome. Transformation-mediated targeting of AFT1-1 and AFT3-1 in NAF8 produced AF-toxin-minus, nonpathogenic mutants. All of the mutants lacked the 1.05-Mb chromosome encoding the AFT genes. This chromosome was not essential for saprophytic growth of this pathogen. Thus, we propose that a conditionally dispensable chromosome controls host-specific pathogenicity of this pathogen.

Full Text

The Full Text of this article is available as a PDF (295K).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Ahn JH, Walton JD. Chromosomal organization of TOX2, a complex locus controlling host-selective toxin biosynthesis in Cochliobolus carbonum. Plant Cell. 1996 May;8(5):887–897. [PMC free article] [PubMed]
  • Akamatsu H, Taga M, Kodama M, Johnson R, Otani H, Kohmoto K. Molecular karyotypes for Alternaria plant pathogens known to produce host-specific toxins. Curr Genet. 1999 Jul;35(6):647–656. [PubMed]
  • Altschul SF, Madden TL, Schäffer AA, Zhang J, Zhang Z, Miller W, Lipman DJ. Gapped BLAST and PSI-BLAST: a new generation of protein database search programs. Nucleic Acids Res. 1997 Sep 1;25(17):3389–3402. [PMC free article] [PubMed]
  • An Z, Farman ML, Budde A, Taura S, Leong SA. New cosmid vectors for library construction, chromosome walking and restriction mapping in filamentous fungi. Gene. 1996 Oct 17;176(1-2):93–96. [PubMed]
  • Chu G, Vollrath D, Davis RW. Separation of large DNA molecules by contour-clamped homogeneous electric fields. Science. 1986 Dec 19;234(4783):1582–1585. [PubMed]
  • Covert SF. Supernumerary chromosomes in filamentous fungi. Curr Genet. 1998 May;33(5):311–319. [PubMed]
  • Covert SF, Enkerli J, Miao VP, VanEtten HD. A gene for maackiain detoxification from a dispensable chromosome of Nectria haematococca. Mol Gen Genet. 1996 Jun 24;251(4):397–406. [PubMed]
  • Elgersma Y, Vos A, van den Berg M, van Roermund CW, van der Sluijs P, Distel B, Tabak HF. Analysis of the carboxyl-terminal peroxisomal targeting signal 1 in a homologous context in Saccharomyces cerevisiae. J Biol Chem. 1996 Oct 18;271(42):26375–26382. [PubMed]
  • Enkerli J, Bhatt G, Covert SF. Nht1, a transposable element cloned from a dispensable chromosome in Nectria haematococca. Mol Plant Microbe Interact. 1997 Aug;10(6):742–749. [PubMed]
  • Han Y, Liu X, Benny U, Kistler HC, VanEtten HD. Genes determining pathogenicity to pea are clustered on a supernumerary chromosome in the fungal plant pathogen Nectria haematococca. Plant J. 2001 Feb;25(3):305–314. [PubMed]
  • Miao VP, Covert SF, VanEtten HD. A fungal gene for antibiotic resistance on a dispensable ("B") chromosome. Science. 1991 Dec 20;254(5039):1773–1776. [PubMed]
  • Miao VP, Matthews DE, VanEtten HD. Identification and chromosomal locations of a family of cytochrome P-450 genes for pisatin detoxification in the fungus Nectria haematococca. Mol Gen Genet. 1991 Apr;226(1-2):214–223. [PubMed]
  • He C, Rusu AG, Poplawski AM, Irwin JA, Manners JM. Transfer of a supernumerary chromosome between vegetatively incompatible biotypes of the fungus Colletotrichum gloeosporioides. Genetics. 1998 Dec;150(4):1459–1466. [PMC free article] [PubMed]
  • Johnson RD, Johnson L, Itoh Y, Kodama M, Otani H, Kohmoto K. Cloning and characterization of a cyclic peptide synthetase gene from Alternaria alternata apple pathotype whose product is involved in AM-toxin synthesis and pathogenicity. Mol Plant Microbe Interact. 2000 Jul;13(7):742–753. [PubMed]
  • Mullaney EJ, Hamer JE, Roberti KA, Yelton MM, Timberlake WE. Primary structure of the trpC gene from Aspergillus nidulans. Mol Gen Genet. 1985;199(1):37–45. [PubMed]
  • Müller-Newen G, Stoffel W. Site-directed mutagenesis of putative active-site amino acid residues of 3,2-trans-enoyl-CoA isomerase, conserved within the low-homology isomerase/hydratase enzyme family. Biochemistry. 1993 Oct 26;32(42):11405–11412. [PubMed]
  • Johnson LJ, Johnson RD, Akamatsu H, Salamiah A, Otani H, Kohmoto K, Kodama M. Spontaneous loss of a conditionally dispensable chromosome from the Alternaria alternata apple pathotype leads to loss of toxin production and pathogenicity. Curr Genet. 2001 Aug;40(1):65–72. [PubMed]
  • Kawamura C, Tsujimoto T, Tsuge T. Targeted disruption of a melanin biosynthesis gene affects conidial development and UV tolerance in the Japanese pear pathotype of Alternaria alternata. Mol Plant Microbe Interact. 1999 Jan;12(1):59–63. [PubMed]
  • Kempken F, Kück U. restless, an active Ac-like transposon from the fungus Tolypocladium inflatum: structure, expression, and alternative RNA splicing. Mol Cell Biol. 1996 Nov;16(11):6563–6572. [PMC free article] [PubMed]
  • Nikolskaya AN, Panaccione DG, Walton JD. Identification of peptide synthetase-encoding genes from filamentous fungi producing host-selective phytotoxins or analogs. Gene. 1995 Nov 20;165(2):207–211. [PubMed]
  • Okuda M, Ikeda K, Namiki F, Nishi K, Tsuge T. Tfo1: an Ac-like transposon from the plant pathogenic fungus Fusarium oxysporum. Mol Gen Genet. 1998 Jun;258(6):599–607. [PubMed]
  • Pavela-Vrancic M, Pfeifer E, van Liempt H, Schäfer HJ, von Döhren H, Kleinkauf H. ATP binding in peptide synthetases: determination of contact sites of the adenine moiety by photoaffinity labeling of tyrocidine synthetase 1 with 2-azidoadenosine triphosphate. Biochemistry. 1994 May 24;33(20):6276–6283. [PubMed]
  • Kusaba M, Tsuge T. Nuclear ribosomal DNA variation and pathogenic specialization in alternaria fungi known to produce host-specific toxins. Appl Environ Microbiol. 1994 Sep;60(9):3055–3062. [PMC free article] [PubMed]
  • Rosewich U Liane, Kistler H Corby. ROLE OF HORIZONTAL GENE TRANSFER IN THE EVOLUTION OF FUNGI. Annu Rev Phytopathol. 2000;38(NaN):325–363. [PubMed]
  • Kusaba M, Tsuge T. Phylogeny of Alternaria fungi known to produce host-specific toxins on the basis of variation in internal transcribed spacers of ribosomal DNA. Curr Genet. 1995 Oct;28(5):491–498. [PubMed]
  • Scheffer RP, Livingston RS. Host-selective toxins and their role in plant diseases. Science. 1984 Jan 6;223(4631):17–21. [PubMed]
  • VanEtten H, Jorgensen S, Enkerli J, Covert SF. Inducing the loss of conditionally dispensable chromosomes in Nectria haematococca during vegetative growth. Curr Genet. 1998 Apr;33(4):299–303. [PubMed]
  • Tanaka A, Tsuge T. Structural and functional complexity of the genomic region controlling AK-toxin biosynthesis and pathogenicity in the Japanese pear pathotype of Alternaria alternata. Mol Plant Microbe Interact. 2000 Sep;13(9):975–986. [PubMed]
  • Walton JD. Host-selective toxins: agents of compatibility. Plant Cell. 1996 Oct;8(10):1723–1733. [PMC free article] [PubMed]
  • Walton JD. Horizontal gene transfer and the evolution of secondary metabolite gene clusters in fungi: an hypothesis. Fungal Genet Biol. 2000 Aug;30(3):167–171. [PubMed]
  • Tanaka A, Shiotani H, Yamamoto M, Tsuge T. Insertional mutagenesis and cloning of the genes required for biosynthesis of the host-specific AK-toxin in the Japanese pear pathotype of Alternaria alternata. Mol Plant Microbe Interact. 1999 Aug;12(8):691–702. [PubMed]
  • Thompson JD, Higgins DG, Gibson TJ. CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice. Nucleic Acids Res. 1994 Nov 11;22(22):4673–4680. [PMC free article] [PubMed]
  • Yang G, Rose MS, Turgeon BG, Yoder OC. A polyketide synthase is required for fungal virulence and production of the polyketide T-toxin. Plant Cell. 1996 Nov;8(11):2139–2150. [PMC free article] [PubMed]
  • Todd RB, Andrianopoulos A. Evolution of a fungal regulatory gene family: the Zn(II)2Cys6 binuclear cluster DNA binding motif. Fungal Genet Biol. 1997 Jun;21(3):388–405. [PubMed]
  • Tsuge T, Nishimura S, Kobayashi H. Efficient integrative transformation of the phytopathogenic fungus Alternaria alternata mediated by the repetitive rDNA sequences. Gene. 1990 Jun 15;90(2):207–214. [PubMed]

Articles from Genetics are provided here courtesy of Genetics Society of America


Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...


Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...