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A saponin-detoxifying enzyme mediates suppression of plant defences


Plant disease resistance can be conferred by constitutive features such as structural barriers or preformed antimicrobial secondary metabolites. Additional defence mechanisms are activated in response to pathogen attack and include localized cell death (the hypersensitive response)1,2. Pathogens use different strategies to counter constitutive and induced plant defences, including degradation of preformed antimicrobial compounds3 and the production of molecules that suppress induced plant defences4,5,6. Here we present evidence for a two-component process in which a fungal pathogen subverts the preformed antimicrobial compounds of its host and uses them to interfere with induced defence responses. Antimicrobial saponins are first hydrolysed by a fungal saponin-detoxifying enzyme. The degradation product of this hydrolysis then suppresses induced defence responses by interfering with fundamental signal transduction processes leading to disease resistance.

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Figure 1: Infection of N. benthamiana by S. lycopersici strains.
Figure 2: Localized cell death induced by tomatinase-deficient mutants of S. lycopersici is SGT1-dependent.
Figure 3: Pre-infiltration with β2-tomatine compromises resistance to 2D2.
Figure 4: β2-Tomatine mediates suppression of bacterial disease resistance in N. benthamiana.


  1. Hammond-Kosack, K. & Jones, J. D. G. in Biochemistry and Molecular Biology of Plants (eds Buchanan, B. B., Gruissem, W. & Jones, R. L.) 1102–1156 (American Society of Plant Physiologists, Rockville, Maryland, 2001)

    Google Scholar 

  2. Flor, H. H. Current status of the gene-for-gene concept. Annu. Rev. Phytopathol. 9, 275–296 (1971)

    Article  Google Scholar 

  3. Morrissey, J. P. & Osbourn, A. E. Fungal resistance to plant antibiotics as a mechanism of pathogenesis. Microbiol. Mol. Biol. Rev. 63, 708–724 (1999)

    CAS  PubMed  PubMed Central  Google Scholar 

  4. Doke, N. et al. in Molecular Genetics of Host-Specific Toxins in Plant Disease (eds Kohmoto, K. & Yoder, O. C.) 331–341 (Kluwer, Dordrecht, 1998)

    Book  Google Scholar 

  5. Shiraishi, T. et al. in Molecular Genetics of Host-Specific Toxins in Plant Disease (eds Kohmoto, K. & Yoder, O. C.) 343–349 (Kluwer, Dordrecht, 1998)

    Book  Google Scholar 

  6. Heath, M. C. Hypersensitive response-related death. Plant Mol. Biol. 44, 321–334 (2002)

    Article  Google Scholar 

  7. Roddick, J. The steroidal glycoalkaloid tomatine. Phytochemistry 13, 9–25 (1974)

    CAS  Article  Google Scholar 

  8. Arneson, P. A. & Durbin, R. D. Studies on the mode of action of tomatine as a fungitoxic agent. Plant Physiol. 43, 683–686 (1968)

    CAS  Article  Google Scholar 

  9. Arneson, P. A. & Durbin, R. D. The sensitivity of fungi to α-tomatine. Phytopathology 58, 536–537 (1968)

    Google Scholar 

  10. Sandrock, R. W., DellaPenna, D. & VanEtten, H. D. Purification and characterization of β2-tomatinase, an enzyme involved in the degradation of α-tomatine and isolation of the gene encoding β2-tomatinase from Septoria lycopersici. Mol. Plant Microbe Interact. 8, 960–970 (1995)

    CAS  Article  Google Scholar 

  11. Sandrock, R. W. & VanEtten, H. D. Fungal sensitivity to and enzymatic degradation of the phytoanticipin α-tomatine. Phytopathology 88, 137–143 (1998)

    CAS  Article  Google Scholar 

  12. Martin-Hernandez, A. M., Dufresne, M., Hugouvieux, V., Melton, R. & Osbourn, A. Effects of targeted replacement of the tomatinase gene on the interaction of Septoria lycopersici with tomato plants. Mol. Plant Microbe Interact. 13, 1301–1311 (2000)

    CAS  Article  Google Scholar 

  13. Arneson, P. A. & Durbin, R. D. Hydrolysis of tomatine by Septoria lycopersici: a detoxification mechanism. Phytopathology 57, 1358–1360 (1967)

    CAS  Google Scholar 

  14. Durbin, R. D. & Uchytil, T. F. Purification and properties of a fungal β-glucosidase acting on α-tomatine. Biochim. Biophys. Acta. 191, 176–178 (1969)

    CAS  Article  Google Scholar 

  15. Osbourn, A. E., Bowyer, P., Lunness, P., Clarke, B. & Daniels, M. Fungal pathogens of oat roots and tomato leaves employ closely related enzymes to detoxify different host plant saponins. Mol. Plant Microbe Interact. 8, 971–978 (1995)

    CAS  Article  Google Scholar 

  16. Sandrock, R. W. & VanEtten, H. D. The relevance of tomatinase activity in pathogens of tomato: disruption of the β2-tomatinase gene in Colletotrichum coccodes and Septoria lycopersici and heterologous expression of the Septoria lycopersici β2-tomatinase in Nectria haematococca, a pathogen of tomato fruit. Physiol. Mol. Plant Pathol. 58, 159–171 (2001)

    CAS  Article  Google Scholar 

  17. Baulcombe, D. C. Fast forward genetics based on virus-induced gene silencing. Curr. Opin. Plant Biol. 2, 109–113 (1999)

    CAS  Article  Google Scholar 

  18. Tronchet, M., Ranty, B., Marco, Y. & Roby, D. HSR203 antisense suppression in tobacco accelerates development of hypersensitive cell death. Plant J. 27, 115–127 (2001)

    CAS  Article  Google Scholar 

  19. Yoshioka, K. et al. Environmentally sensitive, SA-dependent defense responses in the cpr22 mutant of Arabidopsis. Plant J. 26, 447–459 (2001)

    CAS  Article  Google Scholar 

  20. Froehlich, J. E., Itoh, A. & Howe, G. A. Tomato allene oxide synthase and fatty acid hydroperoxide lyase, two cytochrome P450s involved in oxylipin metabolism, are targeted to different membranes of chloroplast envelope. Plant Physiol. 125, 306–317 (2001)

    CAS  Article  Google Scholar 

  21. Ziegler, J., Keinanen, M. & Baldwin, I. T. Herbivore-induced allene oxide synthase transcripts and jasmonic acid in Nicotiana attenuata. Phytochemistry 58, 729–738 (2001)

    CAS  Article  Google Scholar 

  22. Austin, M. J. et al. Regulatory role of SGT1 in early R gene-mediated plant defenses. Science 292, 2077–2080 (2002)

    ADS  Article  Google Scholar 

  23. Azevedo, C. et al. The RAR1 interactor SGT1, an essential component of R gene-triggered disease resistance. Science 292, 2073–2076 (2002)

    ADS  Article  Google Scholar 

  24. Peart, J. et al. SGT1 is required for host and nonhost disease resistance in plants. Proc. Natl Acad. Sci. USA advance online publication, 15 July 2002 (DOI 10.1073/pnas.152330599)

  25. Martin, G. B. et al. Map-based cloning of a protein kinase gene conferring disease resistance in tomato. Science 262, 1432–1436 (1993)

    ADS  CAS  Article  Google Scholar 

  26. Scofield, S. R. et al. Molecular basis of gene-for-gene specificity in bacterial speck disease of tomato. Science 274, 2063–2065 (1996)

    ADS  CAS  Article  Google Scholar 

  27. Rommens, C. M. T., Salmeron, J. M., Oldroyd, G. E. D. & Staskawicz, B. J. Intergenic transfer and functional expression of the tomato disease resistance gene Pto. Plant Cell 7, 1537–1544 (1995)

    CAS  Article  Google Scholar 

  28. Voinnet, O. & Baulcombe, D. Systemic signalling in gene silencing. Nature 389, 553–553 (1997)

    ADS  CAS  Article  Google Scholar 

  29. Singh, S., Khanna, N. M. & Dhar, M. M. Solaplumbin, a new anticancer glycoside from Nicotiana plumbaginifolia. Phytochemistry 13, 2020–2022 (1974)

    CAS  Article  Google Scholar 

  30. Grünweller, S., Schröder, E. & Kesselmeier, J. Biological activities of furostanol saponins from Nicotiana tabacum. Phytochemistry 29, 2485–2490 (1990)

    Article  Google Scholar 

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We thank R. Sandrock and H. Van Etten for strains of S. lycopersici; P. Moffett for supplying SGT1-silenced N. benthamiana plants; and D. Holden and J. Rathjen for criticism of the manuscript. K.B. is supported by a Marie Curie European Community fellowship and the Sainsbury Laboratory is supported by the Gatsby Charitable Foundation.

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Correspondence to A. Osbourn.

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Bouarab, K., Melton, R., Peart, J. et al. A saponin-detoxifying enzyme mediates suppression of plant defences. Nature 418, 889–892 (2002).

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