Increased disease susceptibility of transgenic tobacco plants with suppressed levels of preformed phenylpropanoid products

Eileen A. Maher, Nicholas J. Bate, Weiting Ni, Yonatan Elkind, Richard A. Dixon, Chris J. Lamb*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

231 Scopus citations


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 ammonia- lyase, EC 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.

Original languageAmerican English
Pages (from-to)7802-7806
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number16
StatePublished - 2 Aug 1994


  • chlorogenic acid
  • cosuppression
  • natural product functions
  • phenylalanine ammonia-lyase
  • plant disease resistance


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