Inverse relationship between systemic resistance of plants to microorganisms and to insect herbivory

G. W. Felton, K. L. Korth, J. L. Bi, S. V. Wesley, D. V. Huhman, M. C. Mathews, J. B. Murphy, C. Lamb, R. A. Dixon

Research output: Contribution to journalArticlepeer-review

219 Scopus citations

Abstract

Pre-inoculation of plants with a pathogen that induces necrosis leads to the development of systemic acquired resistance (SAR) to subsequent pathogen attack [1]. The phenylpropanoid-derived compound salicylic acid (SA) is necessary for the full expression of both local resistance and SAR [2,3]. A separate signaling pathway involving jasmonic acid (JA) is involved in systemic responses to wounding and insect herbivory [4,5]. There is evidence both supporting and opposing the idea of cross-protection against microbial pathogens and insect herbivores [6,7]. This is a controversial area because pharmacological experiments point to negative cross-talk between responses to systemic pathogens and responses to wounding [8-10], although this has not been demonstrated functionally in vivo. Here, we report that reducing phenylpropanoid biosynthesis by silencing the expression of phenylalanine ammonia-lyase (PAL) reduces SAR to tobacco mosaic virus (TMV), whereas overexpression of PAL enhances SAR. Tobacco plants with reduced SAR exhibited more effective grazing-induced systemic resistance to larvae of Heliothis virescens, but larval resistance was reduced in plants with elevated phenylpropanoid levels. Furthermore, genetic modification of components involved in phenylpropanoid synthesis revealed an inverse relationship between SA and JA levels. These results demonstrate phenylpropanoid-mediated cross-talk in vivo between microbially induced and herbivore-induced pathways of systemic resistance.

Original languageEnglish (US)
Pages (from-to)317-320
Number of pages4
JournalCurrent Biology
Volume9
Issue number6
DOIs
StatePublished - Mar 25 1999

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

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