title: Jasmonate-Inducible Genes Are Activated in Rice by Pathogen Attack without a Concomitant Increase in Endogenous Jasmonic Acid Levels.
abstract: The possible role of the octadecanoid signaling pathway with jasmonic acid (JA) as the central component in defense-gene regulation of pathogen-attacked rice was studied. Rice (Oryza sativa L.) seedlings were treated with JA or inoculated with the rice blast fungus Magnaporthe grisea (Hebert) Barr., and gene-expression patterns were compared between the two treatments. JA application induced the accumulation of a number of pathogenesis-related (PR) gene products at the mRNA and protein levels, but pathogen attack did not enhance the levels of (-)-JA during the time required for PR gene expression. Pathogen-induced accumulation of PR1-like proteins was reduced in plants treated with tetcyclacis, a novel inhibitor of jasmonate biosynthesis. There was an additive and negative interaction between JA and an elicitor from M. grisea with respect to induction of PR1-like proteins and of an abundant JA-and wound-induced protein of 26 kD, respectively. Finally, activation of the octadecanoid signaling pathway and induction of a number of PR genes by exogenous application of JA did not confer local acquired resistance to rice. The data suggest that accumulation of nonconjugated (-)-JA is not necessary for induction of PR genes and that JA does not orchestrate localized defense responses in pathogen-attacked rice. Instead, JA appears to be embedded in a signaling network with another pathogen-induced pathway(s) and may be required at a certain minimal level for induction of some PR genes.
authors.affiliation: Institut de Biologie Vegetale, University of Fribourg, Rte Albert-Gockel 3, CH-1700 Fribourg, Switzerland (P. Schweizer, A.B., J.-P.M.).
authors.forename: P.
authors.initials: P
authors.lastname: Schweizer
authors.forename: A.
authors.initials: A
authors.lastname: Buchala
authors.forename: P.
authors.initials: P
authors.lastname: Silverman
authors.forename: M.
authors.initials: M
authors.lastname: Seskar
authors.forename: I.
authors.initials: I
authors.lastname: Raskin
authors.forename: J. P.
authors.initials: JP
authors.lastname: Metraux