Antagonistic Effect of Salicylic Acid and Jasmonic Acid on the Expression of Pathogenesis-Related (PR) Protein Genes in Wounded Mature Tobacco Leaves

Abstract

Salicylic acid (SA) and jasmonic acid (JA) are essential compounds in the pathogen- and wound-signaling pathways accompanying induced expression of acidic and basic pathogenesis-related (PR) protein genes, respectively. However, on the effect of exogenously supplied SA and JA in induction of PR gene expression, conflicting results have been obtained using various plant materials at different developmental stages. There is no clear evidence on these effects in the presence of both signals at the same time. We analyzed the effect of SA on wound- and JA-induced basic PR gene expression and that of JA on SA-induced acidic Pi? gene expression in mature tobacco leaves. Wound-induced accumulation of transcripts for all 4 basic PR genes tested was enhanced in the presence of MeJA, and inhibited in the presence of SA. On the other hand, expression of all 3 acidic PR genes tested was induced by SA and was inhibited by MeJA. Using antibodies raised against acidic PR-1 and PR-2 proteins, these effects were confirmed at the protein level. These results indicated that JA works as an inducer of basic PR genes, and also as an inhibitor for acidic PR genes, while SA does the opposite.