Salicylic acid is not required for Cf-2- and Cf-9-dependent resistance of tomato to Cladosporium fulvum

Authors

  • Penny A. Brading,

    1. Sainsbury Laboratory, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK, and
    Search for more papers by this author
    • Present address: Cereals Research Department, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK.

  • Kim E. Hammond-Kosack,

    1. Sainsbury Laboratory, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK, and
    Search for more papers by this author
    • Present address: Monsanto PLC, Cereal Technology Group, Maris Lane, Trumpington, Cambridge CB2 2LQ, UK.

  • Adrian Parr,

    1. Institute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4 7UA, UK
    Search for more papers by this author
  • Jonathan D. G. Jones

    Corresponding author
    1. Sainsbury Laboratory, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK, and
      For correspondence (fax +44 1603 250024; e-mail
    Search for more papers by this author

For correspondence (fax +44 1603 250024; e-mail jonathan.jones@bbsrc.ac.uk).

Summary

Tomato leaves or cotyledons expressing the Cf-2 or Cf-9 Cladosporium fulvum resistance genes induce salicylic acid (SA) synthesis following infiltration with intercellular washing fluid (IF) containing the fungal peptide elicitors Avr2 and Avr9. We investigated whether SA was required for Cf gene-dependent resistance. Tomato plants expressing the bacterial gene nahG, encoding salicylate hydroxylase, did not accumulate SA in response to IF infiltration but remained fully resistant to C. fulvum. NahG Cf0 plants were as susceptible to C. fulvum as wild-type Cf0. Neither free nor conjugated salicylic acid accumulated in IF-infiltrated Cf2 and Cf9 NahG leaves and cotyledons but conjugated catechol did accumulate. The Cf-9-dependent necrotic response to IF was prevented in NahG plants and replaced by a chlorotic Cf-2-like response. SA also potentiated Cf-9-mediated necrosis in IF-infiltrated wild-type leaves. In contrast, the Cf-2-dependent IF response was retained in NahG leaves and chlorosis was more pronounced than in the wild-type. The distribution of cell death between different cell types was altered in both Cf2 and Cf9 NahG leaves after IF injection. IF-induced accumulation of three SA-inducible defence-related genes was delayed and reduced but not abolished in NahG Cf2 and Cf9 leaves and cotyledons. NahG Tm-22 tomato showed increased hypersensitive response (HR) lesion size upon TMV infection, as observed in TMV-inoculated N gene-containing NahG tobacco plants.

Ancillary