Salicylate-mediated suppression of jasmonate-responsive gene expression in Arabidopsis is targeted downstream of the jasmonate biosynthesis pathway

Abstract

Jasmonates (JAs) and salicylic acid (SA) are plant hormones that play pivotal roles in the regulation of induced defenses against microbial pathogens and insect herbivores. Their signaling pathways cross-communicate providing the plant with a regulatory potential to finely tune its defense response to the attacker(s) encountered. In Arabidopsis thaliana, SA strongly antagonizes the jasmonic acid (JA) signaling pathway, resulting in the downregulation of a large set of JA-responsive genes, including the marker genes PDF1.2 and VSP2. Induction of JA-responsive marker gene expression by different JA derivatives was equally sensitive to SA-mediated suppression. Activation of genes encoding key enzymes in the JA biosynthesis pathway, such as LOX2, AOS, AOC2, and OPR3 was also repressed by SA, suggesting that the JA biosynthesis pathway may be a target for SA-mediated antagonism. To test this, we made use of the mutant aos/dde2, which is completely blocked in its ability to produce JAs because of a mutation in the ALLENE OXIDE SYNTHASE gene. Mutant aos/dde2 plants did not express the JA-responsive marker genes PDF1.2 or VSP2 in response to infection with the necrotrophic fungus Alternaria brassicicola or the herbivorous insect Pieris rapae. Bypassing JA biosynthesis by exogenous application of methyl jasmonate (MeJA) rescued this JA-responsive phenotype in aos/dde2. Application of SA suppressed MeJA-induced PDF1.2 expression to the same level in the aos/dde2 mutant as in wild-type Col-0 plants, indicating that SA-mediated suppression of JA-responsive gene expression is targeted at a position downstream of the JA biosynthesis pathway.

RNA interference of the nicotine demethylase gene CYP82E4v1 reduces nornicotine content and enhances Myzus persicae resistance in Nicotiana tabacum L

“…expression of salicylic acid (SA)-responsive gene was inhibited by the higher expression of jasmonic acid (JA)-responsive gene, which was similar to the results of salicylate-mediated suppression of jasmonate-responsive gene expression in Arabidopsis(Leon-Reyes et al, 2010). Moreover, the relatively higher expression of LOX gene indicated the products encoded by the gene might involve in resistance response at ealy stage.…”

Botrytis cinerea Manipulates the Antagonistic Effects between Immune Pathways to Promote Disease Development in Tomato

“…Doares et al (1995) provided evidence that exogenous application of SA to tomato plants strongly inhibits the JA-induced expression of genes encoding PI I and II, suggesting that SA targets the JA pathway downstream of JA biosynthesis. Recently, Leon-Reyes et al (2010) showed that SA-mediated suppression of JA-responsive gene expression in Arabidopsis is targeted downstream of the jasmonate biosynthesis pathway. NPR1 and the TGA (for thymine, guanine, and adenine nucleotides) binding sequence protein family are important for the SA signaling pathway (Loake and Grant, 2007).…”

Oxidative stress homeostasis in grapevine (Vitis vinifera L.)

“…The activity of JA responses can be regulated by antagonistic cross-talk with SA signaling (for review, Balbi and Devoto, 2008). In fact, SA can suppress the JAdependent response to wounding and pathogen or insect attack (Leon-Reyes et al, 2010).…”