September
2002
, Volume
15
, Number
9
Pages
883
-
893
Authors
Mark S.
Rose
,
Sung-Hwan
Yun
,
Thipa
Asvarak
,
Shun-Wen
Lu
,
O. C.
Yoder
,
and
B. Gillian
Turgeon
Affiliations
Department of Plant Pathology, Cornell University, Ithaca, NY 14853 U.S.A.
Go to article:
RelatedArticle
Accepted 22 April 2002.
Abstract
Genes at two unlinked loci (Tox1A and Tox1B) are required for production of the polyketide T-toxin by Cochliobolus heterostrophus race T, a pathogenic fungus that requires T-toxin for high virulence to maize with T-cytoplasm. Previous work indicated that Tox1A encodes a polyketide synthase (PKS1) required for T-toxin biosynthesis and for high virulence. To identify genes at Tox1B, a wild-type race T cDNA library was screened for genes missing in the genome of a Tox1B deletion mutant. The library was probed, first with a 415-kb NotI restriction fragment from the genome of the Tox1B¯ mutant, then with the corresponding 560-kb fragment from the genome of wild type. Two genes, DEC1 (similar to aceto-acetate decarboxylase-encoding genes) and RED1 (similar to genes encoding members of the medium-chain dehydro-genase/reductase superfamily), were recovered. Targeted disruption of DEC1 drastically reduced both T-toxin production and virulence of race T to T-cytoplasm maize, whereas specific inactivation of RED1 had no apparent effect on T-toxin production (as determined by bioassay) or on virulence. DEC1 and RED1 map within 1.5 kb of each other on Tox1B chromosome 6;12 and are unique to the genome of race T, an observation consistent with the hypothesis that these genes were acquired by C. heterostrophus via a horizontal transfer event.
JnArticleKeywords
Additional keywords:
Mycosphaerella zeae-maydis
,
race O.
Page Content
ArticleCopyright
© 2002 The American Phytopathological Society