Negative cross‐talk between salicylate‐ and jasmonate‐mediated pathways in the Wassilewskija ecotype of Arabidopsis thaliana

Abstract

Plants often respond to attack by insect herbivores and necrotrophic pathogens with induction of jasmonate-dependent resistance traits, but respond to attack by biotrophic pathogens with induction of salicylate-dependent resistance traits. To assess the degree to which the jasmonate- and salicylate-dependent pathways interact, we compared pathogenesis-related protein activity and bacterial performance in four mutant Arabidopsis thaliana lines relative to their wild-type backgrounds. We found that two salicylate-dependent pathway mutants (cep1, nim1-1) exhibited strong effects on the growth of the generalist biotrophic pathogen, Pseudomonas syringae pv. tomato, whereas two jasmonate-dependent pathway mutants (fad3-2fad7-2fad8, jar1-1) did not. Leaf peroxidase and exochitinase activity were negatively correlated with bacterial growth, whereas leaf polyphenol oxidase activity and trypsin inhibitor concentration were not. Interestingly, leaf total glucosinolate concentration was positively correlated with bacterial growth. In the same experiment, we also found that application of jasmonic acid generally increased leaf peroxidase activity and trypsin inhibitor concentration in the mutant lines. However, the cep1 mutant, shown previously to overexpress salicylic acid, exhibited no detectable biological or chemical responses to jasmonic acid, suggesting that high levels of salicylic acid may have inhibited a plant response. In a second experiment, we compared the effect of jasmonic acid and/or salicylic acid on two ecotypes of A. thaliana. Application of salicylic acid to the Wassilewskija ecotype decreased bacterial growth. However, this effect was not observed when both salicylic acid and jasmonic acid were applied, suggesting that jasmonic acid negated the beneficial effect of salicylic acid. Collectively, our results confirm that the salicylate-dependent pathway is more important than the jasmonate-dependent pathway in determining growth of P. syringae pv. tomato in A. thaliana, and suggest important negative interactions between these two major defensive pathways in the Wassilewskija ecotype. In contrast, the Columbia ecotype exhibited little evidence of negative interactions between the two pathways, suggesting intraspecific variability in how these pathways interact in A. thaliana.

Induced Resistance in Mycorrhizal Tomato is correlated to Concentration of Jasmonic Acid

“…Increase in levels of endogenous jasmonates are followed by activation of genes involved in plant defence responses such as those coding for enzymes of phytoalexins synthesis, vegetative storage proteins [23,35] . Studies have shown that increase in endogenous level of jasmonic acid results in induction of trichomes [49] and present results confirm such reports where a strong positive correlation was observed between trichome density of leaves and endogenous level of jasmonic acid. Present results therefore provide evidence that AMF regulate systemic increase in physical defence in tomato by increasing the concentration of JA.…”

Methyl Salicylate Production and Jasmonate Signaling Are Not Essential for Systemic Acquired Resistance inArabidopsis

“…In addition to MeSA volatilization, SAG formation and subsequent vacuolar storage is an alternative way to handle an excess of SA (Lee et al, 1995;Dean et al, 2005). MeSA formation might also influence the interplay between SA and JA, which trigger distinct sets of defense responses and thereby often behave in a counteractive manner (Traw et al, 2003;Koornneef et al, 2008). JA-mediated MeSA production and subsequent release of the volatile might thus be one means by which negative crosstalk between SA and JA signaling is realized.…”

Differential Activity of Peroxidase Isozymes in Response to Wounding, Gypsy Moth, and Plant Hormones in Northern Red Oak (Quercus rubra L.)

“…Like the differential greenhouse responses to GM, wounding, and JA, this also suggests that red oak POD responses may be unique to the attacking insect. While studies of POD in the context of herbivory have focused on total POD activity (e.g., Cipollini and Redman, 1999;Mayer et al, 2002;Roitto et al, 2003;Traw et al, 2003), the plant pathology literature provides many examples of pathogen-specific POD isoform activity or profiles (Kristensen et al, 1999;Kandan et al, 2002;Tognolli et al, 2002;Maksimov et al, 2003). In some cases, POD isoform function is based on hostplant substrate specificity and the production of specific defenses (Calderón et al, 1990).…”