Increased Disease Susceptibility of Transgenic Tobbacco Plants with Suppressed Levels of Preformed Phenylpropanoid Products

It has been proposed that natural products synthesized by plants contribute to their resistance to pests and pathogens. We show here that transgenic tobacco plants with suppressed levels of the phenylpropanoid biosynthetic enzyme phenylalanine ammonia-lyase (L-phenylalanine ammonialyase, EC 4.3.1.5)...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1994-08, Vol.91 (16), p.7802-7806
Main Authors: Eileen A. Maher, Nicholas J. Bate, Weiting Ni, Yonatan Elkind, Richard A. Dixon, Chris J. Lamb
Format: Article
Language:English
Subjects:
Developmental biology
Disease susceptibility
Inductive reasoning
Infections
Inoculation
Leaves
Lesions
Pathogens
Plant diseases
Transgenic plants
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Summary:It has been proposed that natural products synthesized by plants contribute to their resistance to pests and pathogens. We show here that transgenic tobacco plants with suppressed levels of the phenylpropanoid biosynthetic enzyme phenylalanine ammonia-lyase (L-phenylalanine ammonialyase, EC 4.3.1.5) and correspondingly low levels of chlorogenic acid, the major soluble leaf phenylpropanoid product, exhibit more rapid and extensive lesion development than wild-type plants after infection by the virulent fungal pathogen Cercospora nicotianae. These observations provide direct evidence that phenylpropanoid products contribute to disease limitation. No induction of transcripts encoding phenylalanine ammonia-lyase or the lignin branch pathway enzyme caffeic acid O-methyltransferase was observed during the infection and there was no perturbation in the pattern of soluble phenylpropanoids. Hence, increased disease susceptibility does not involve inhibition of a pathogen-induced response but likely reflects inhibition of the developmental accumulation of chlorogenic acid. Demonstration of the contribution of such preformed protectants to plant health identifies attractive targets for manipulation by breeding or gene transfer to reduce the quantitative impact of disease.
ISSN:0027-8424
1091-6490