• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of plntcellLink to Publisher's site
Plant Cell. May 1996; 8(5): 887–897.
PMCID: PMC161146

Chromosomal organization of TOX2, a complex locus controlling host-selective toxin biosynthesis in Cochliobolus carbonum.

Abstract

Race 1 isolates of the filamentous fungus Cochliobolus carbonum are exceptionally virulent on certain genotypes of maize due to production of a cyclic tetrapeptide, HC-toxin. In crosses between toxin-producing (Tox2+) and toxin-nonproducing (Tox2-) isolates, toxin production segregates in a simple 1:1 pattern, suggesting the involvement of a single genetic locus, which has been named TOX2. Earlier work had shown that in isolate SB111, TOX2 consists in part of two copies of a gene, HTS1, that encodes a 570-kD cyclic peptide synthetase and is lacking in Tox2- isolates. The genomic structure of TOX2 and the relationship between the two copies of HTS1 have now been clarified by using pulsedfield gel electrophoresis and physical mapping. In isolate SB111, both copies of HTS1 are on the largest chromosome (3.5 Mb), which is not present in the related Tox2- strain SB114. Two other genes known or thought to be important for HC-toxin biosynthesis, TOXA and TOXC, are also on the same chromosome in multiple copies. Other independent Tox2+ isolates also have two linked copies of HTS1, but in some isolates the size of the chromosome containing HTS1 is 2.2 Mb. Evidence obtained with Tox2+ -unique and with random probes is consistent with a reciprocal translocation as the cause of the difference in the size of the HTS1-containing chromosome among the Tox2+ isolates studied here. Physical mapping of the 3.5-Mb chromosome of SB111 that contains HTS1 using rare-cutting restriction enzymes and engineered restriction sites was used to map the chromosome location of the two copies of HTS1 and the three copies of TOXC. The results indicate that TOX2 is a complex locus that extends over more than 500 kb. The capacity to produce HC-toxin did not evolve by any single, simple mechanism.

Full Text

The Full Text of this article is available as a PDF (3.0M).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Masel AM, Irwin JA, Manners JM. DNA addition or deletion is associated with a major karyotype polymorphism in the fungal phytopathogen Colletotrichum gloeosporioides. Mol Gen Genet. 1993 Feb;237(1-2):73–80. [PubMed]
  • Apel PC, Panaccione DG, Holden FR, Walton JD. Cloning and targeted gene disruption of XYL1, a beta 1,4-xylanase gene from the maize pathogen Cochliobolus carbonum. Mol Plant Microbe Interact. 1993 Jul-Aug;6(4):467–473. [PubMed]
  • Hohn TM, McCormick SP, Desjardins AE. Evidence for a gene cluster involving trichothecene-pathway biosynthetic genes in Fusarium sporotrichioides. Curr Genet. 1993 Oct;24(4):291–295. [PubMed]
  • Lim SM, Hooker AL. Southern Corn Leaf Blight: Genetic Control of Pathogenicity and Toxin Production in Race T and Race O of COCHLIOBOLUS HETEROSTROPHUS. Genetics. 1971 Sep;69(1):115–117. [PMC free article] [PubMed]
  • Lu S, Lyngholm L, Yang G, Bronson C, Yoder OC, Turgeon BG. Tagged mutations at the Tox1 locus of Cochliobolus heterostrophus by restriction enzyme-mediated integration. Proc Natl Acad Sci U S A. 1994 Dec 20;91(26):12649–12653. [PMC free article] [PubMed]
  • Masel AM, Irwin JA, Manners JM. DNA addition or deletion is associated with a major karyotype polymorphism in the fungal phytopathogen Colletotrichum gloeosporioides. Mol Gen Genet. 1993 Feb;237(1-2):73–80. [PubMed]
  • Panaccione DG, Scott-Craig JS, Pocard JA, Walton JD. A cyclic peptide synthetase gene required for pathogenicity of the fungus Cochliobolus carbonum on maize. Proc Natl Acad Sci U S A. 1992 Jul 15;89(14):6590–6594. [PMC free article] [PubMed]
  • Sposato P, Ahn JH, Walton JD. Characterization and disruption of a gene in the maize pathogen Cochliobolus carbonum encoding a cellulase lacking a cellulose binding domain and hinge region. Mol Plant Microbe Interact. 1995 Jul-Aug;8(4):602–609. [PubMed]
  • Turgeon BG, Garber RC, Yoder OC. Development of a fungal transformation system based on selection of sequences with promoter activity. Mol Cell Biol. 1987 Sep;7(9):3297–3305. [PMC free article] [PubMed]
  • Tzeng TH, Lyngholm LK, Ford CF, Bronson CR. A restriction fragment length polymorphism map and electrophoretic karyotype of the fungal maize pathogen Cochliobolus heterostrophus. Genetics. 1992 Jan;130(1):81–96. [PMC free article] [PubMed]
  • Walton JD. Two enzymes involved in biosynthesis of the host-selective phytotoxin HC-toxin. Proc Natl Acad Sci U S A. 1987 Dec;84(23):8444–8447. [PMC free article] [PubMed]
  • Wang Y, Wu R. A new method for specific cleavage of megabase-size chromosomal DNA by lambda-terminase. Nucleic Acids Res. 1993 May 11;21(9):2143–2147. [PMC free article] [PubMed]
  • Zolan ME. Chromosome-length polymorphism in fungi. Microbiol Rev. 1995 Dec;59(4):686–698. [PMC free article] [PubMed]

Articles from The Plant Cell are provided here courtesy of American Society of Plant Biologists

Formats:

Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...

Links

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...