Abscisic acid determines basal susceptibility of tomato to Botrytis cinerea and suppresses salicylic acid-dependent signaling mechanisms.
Abscisic acid (ABA) is one of the plant hormones involved in the interaction between plants and pathogens. In this work, we show that tomato (Lycopersicon esculentum Mill. cv Moneymaker) mutants with reduced ABA levels (sitiens plants) are much more resistant to the necrotrophic fungus Botrytis cinerea than wild-type (WT) plants. Exogenous application of ABA restored susceptibility to B. cinerea in sitiens plants and increased susceptibility in WT plants. These results indicate that ABA plays a major role in the susceptibility of tomato to B. cinerea. ABA appeared to interact with a functional plant defense response against B. cinerea. Experiments with transgenic NahG tomato plants and benzo(1,2,3)thiadiazole-7-carbothioic acid demonstrated the importance of salicylic acid in the tomato-B. cinerea interaction. In addition, upon infection with B. cinerea, sitiens plants showed a clear increase in phenylalanine ammonia lyase activity, which was not observed in infected WT plants, indicating that the ABA levels in healthy WT tomato plants partly repress phenylalanine ammonia lyase activity. In addition, sitiens plants became more sensitive to benzo(1,2,3)thiadiazole-7-carbothioic acid root treatment. The threshold values for PR1a gene expression declined with a factor 10 to 100 in sitiens compared with WT plants. Thus, ABA appears to negatively modulate the salicylic acid-dependent defense pathway in tomato, which may be one of the mechanisms by which ABA levels determine susceptibility to B. cinerea.
Audenaert
Kris
K
Laboratory of Phytopathology, Faculty of Agricultural and Applied Biological Sciences, Ghent University, Coupure Links, 653, B-9000 Gent, Belgium.
De Meyer
Geert B
GB
Höfte
Monica M
MM
D000040:Abscisic Acid / Q000494:pharmacology*; D020171:Botrytis / Q000472:pathogenicity*; D003517:Cyclopentanes / Q000494:pharmacology; D007113:Immunity, Innate / Q000187:drug effects; D018551:Solanum lycopersicum / Q000187:drug effects* / Q000235:genetics / Q000382:microbiology; D009154:Mutation; D054883:Oxylipins; D010650:Phenylalanine Ammonia-Lyase / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology; D010937:Plant Growth Regulators / Q000494:pharmacology*; D030821:Plants, Genetically Modified; D020156:Salicylic Acid / Q000378:metabolism*; D015398:Signal Transduction; D013830:Thiadiazoles / Q000494:pharmacology
D003517:Cyclopentanes; D054883:Oxylipins; D010937:Plant Growth Regulators; D013830:Thiadiazoles; C011006:jasmonic acid; D000040:Abscisic Acid; C099403:S-methyl benzo(1,2,3)thiadiazole-7-carbothioate; D010650:Phenylalanine Ammonia-Lyase; D020156:Salicylic Acid