期刊
MOLECULAR PLANT-MICROBE INTERACTIONS
卷 16, 期 7, 页码 588-599出版社
AMER PHYTOPATHOLOGICAL SOC
DOI: 10.1094/MPMI.2003.16.7.588
关键词
cell death
Salicylic acid (SA), ethylene, and jasmonic acid (JA) are important signaling molecules in plant defense to biotic stress. An intricate signaling network involving SA, ethylene, and JA fine tunes plant defense responses. SA-dependent defense responses in Arabidopsis thaliana are mediated through NPR1-dependent and -independent mechanisms. We have previously shown that activation of an NPR1-independent defense mechanism confers enhanced disease resistance and constitutive expression of the pathogenesis-related (PR) genes in the Arabidopsis ssil mutant. In addition, the ssil mutant constitutively expresses the defensin gene PDF1.2. Moreover, SA is required for the ssil-conferred constitutive expression of PDF1.2 in addition to PR genes. Hence, the ssil mutant appears to target a step common to SA- and ethylene- or JA-regulated defense pathways. In the present study, we show that, in addition to SA, ethylene and JA signaling also are required for the ssil-conferred constitutive expression of PDF1.2 and the NPR1-independent expression of PR-1. Furthermore, the ethylene-insensitive ein2 and JA-insensitive jar1 mutants enhance susceptibility of ssil plants to the necrotrophic fungus Botrytis cinerea. However, defects in either the ethylene- or JA-signaling pathways do not compromise ssil-conferred resistance to the bacterial pathogen Pseudomonas syringae pv. maculicola and the oomycete pathogen Peronospora parasitica. Interestingly, ssil exhibits a marginal increase in the levels of ethylene and JA, suggesting that low endogenous levels of these phytohormones are sufficient to activate expression of defense genes. Taken together, our results indicate that although cross talk in ssil renders expression of ethylene- or JA-responsive defense genes sensitive to SA and vice versa, it does not affect downstream signaling leading to resistance.
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