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Factors regulating the synthesis of a cyclic peptide pathotoxin produced by Cochliobolus carbonum

Published online by Cambridge University Press:  01 November 1998

MARGARET J. JONES  and
LARRY D. DUNKLE
MARGARET J. JONES
Affiliation:
United States Department of Agriculture, Agricultural Research Service, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907–1155 U.S.A. Present address: United States Department of Agriculture, Agricultural Research Service, Department of Entomology, Purdue University, West Lafayette, Indiana 47907–1158 U.S.A.
LARRY D. DUNKLE
Affiliation:
United States Department of Agriculture, Agricultural Research Service, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907–1155 U.S.A.
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Abstract

The cyclic tetrapeptide, HC-toxin, is a host-selective virulence determinant produced by the foliar pathogen of maize, Cochliobolus carbonum race 1. HC-toxin is synthesized by a multifunctional peptide synthetase (HTS) encoded by the HTS1 gene. Analyses of culture filtrates identified low toxin-producing and high toxin-producing strains among field isolates of the pathogen. These strains were analyzed by reverse transcription PCR to determine whether synthesis of the toxin is directly influenced by HTS1 transcript levels. The results indicated that expression of HTS1 was up-regulated and reached maximal levels several days before the toxin was detected in the culture medium and that HTS1 transcript levels were not correlated with toxigenicity. These observations suggest that genes in addition to HTS1 are involved in regulation of HC-toxin biosynthesis. The toxin-producing ability of low toxin-producing isolates was enhanced following inoculation and reisolation from leaves of susceptible maize genotypes, suggesting that additional factors within the host environment influence toxin production during pathogenesis.

Type
Research Article
Information
Mycological Research , Volume 102 , Issue 11 , November 1998 , pp. 1381 - 1386
Copyright
© The British Mycological Society 1998

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