One enzyme makes a fungal pathogen, but not a saprophyte, virulent on a new host plant

Certain genes of Nectria haematococca, a fungal pathogen of pea (Pisum sativum), encode pisatin demethylase (pda), a cytochrome P-450 monoxygenase that detoxifies the phytoalexin pisatin. Because pda is required by N. haematococca for pathogenicity on pea, pisatin helps defend pea against N. haemato...

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Published in:Science (American Association for the Advancement of Science) 1989-10, Vol.246 (4927), p.247-249
Main Authors: Schäfer, W., Straney, D., Ciuffetti, L., Van Etten, H. D., Yoder, O. C.
Format: Article
Language:English
Subjects:
Ascomycota
aspergillus
Aspergillus nidulans
Biology
cochliobolus
Cochliobolus heterostrophus
Corn
Diseases and pests
enzimas
enzyme
enzymes
fitoalexina
Flowers & plants
Fungi
Fungi, Pathogenic
Lesions
nectria
Pathogenic fungi
Pathogens
Peas
phytoalexine
phytoalexins
Pisum sativum
Plants
Plants (Organisms)
Plasmids
Saprophytes
Saprophytism
zea mays
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Summary:Certain genes of Nectria haematococca, a fungal pathogen of pea (Pisum sativum), encode pisatin demethylase (pda), a cytochrome P-450 monoxygenase that detoxifies the phytoalexin pisatin. Because pda is required by N. haematococca for pathogenicity on pea, pisatin helps defend pea against N. haematococca. The possibility that pistain is a general defense factor--that is, that pda can confer pathogenicity to fungi not normally pathogenic on pea--was investigated. Genes encoding pda were transformed into and highly expressed in Cochliobolus heterostrophus, a fungal pathogen of maize but not of pea, and in Aspergillus nidulans, a saprophytic fungus, neither of which produces a significant amount of pda. Transformants contained at least as much pda as did wild-type N. haematococca. Recombinant C. heterostrophus was normally virulent on maize, but it also caused symptoms on pea, whereas recombinant A. nidulans did not affect pea. Thus, phytoalexins can function in nonspecific resistance of plants to microbes; saprophytes appear to lack genes for basic pathogenicity.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.246.4927.247