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

Abstract

SummaryTomato leaves or cotyledons expressing the Cf-2 or Cf-9 Cladosporium fulvum resistance genes induce salicylic acid (SA) synthesis following in®ltration with intercellular washing¯uid (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 in®ltration 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-in®ltrated 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-in®ltrated 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-2 2 tomato showed increased hypersensitive response (HR) lesion size upon TMV infection, as observed in TMVinoculated N gene-containing NahG tobacco plants.

Identification of defence metabolites in tomato plants infected by the bacterial pathogen Pseudomonas syringae

“…Seeds from tomato (Solanum lycopersicon cultivar Rutgers) (Western Hybrid Seeds Inc., Hamilton City, CA, U.S.A.), transgenic tomato plants overexpressing the bacterial SA hydroxylase transgene (NahG gene) (Brading et al, 2000) or from MoneyMaker (the isogenic parental line for NahG), kindly provided by Professor J.D.G. Jones (John Innes Centre, Norwich, U.K.), were used in this study.…”

“…This posed the question of whether the pathogen-enhanced level of SA could act as a signal to induce the accumulation of HCAA after infection. To correlate the presence of SA with the induction of these metabolites, transgenic NahG tomato plants harbouring a bacterial salicylate hydroxylase which eliminates SA by 595 converting it to catechol (Brading et al, 2000), were infected with P. syringae.…”

Ethylene-mediated cross-talk between calcium-dependent protein kinase and MAPK signaling controls stress responses in plants

“…Free and total SA values were determined as described in ref. 27. For ethylene determination, leaf discs from four independent plants (100 mg of fresh weight in total) per sample were harvested before and 1 h after elicitation into a glass vial that was sealed air-tight and incubated at room temperature for 30 min before storage at Ϫ80°C.…”

Induction of a leaf specific geranylgeranyl pyrophosphate synthase and emission of (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene in tomato are dependent on both jasmonic acid and salicylic acid signaling pathways

“…Castlemart, def-1 (Howe and Ryan 1999), cv. Moneymaker (obtained from the Glasshouse Crop Research Institute (GCRI), now Horticultural Research Institute (HRI), UK) and NahG (Brading et al 2000)] were grown as described by Kant et al (2004). The two-spotted spider mite (Tetranychus urticae Koch) was originally obtained in 1993 from tomato plants in a greenhouse (Houten, The Netherlands; Gotoh et al 1993) and was maintained on the cultivar Moneymaker ever since.…”

“…To investigate whether emission of TMTT is dependent on JA or SA, we made use of the mutant def-1 that is disturbed in the JA-response and the transgenic NahG line that overexpresses the Pseudomonas putida salicylate hydroxylase gene (nahG), resulting in inactivation of SA by converting it into catechol (Brading et al 2000). Def-1 plants have previously been shown to emit signiWcantly lower amounts of TMTT than wild type plants after spider mite-attack ).…”