1Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland; 2Novartis Crop Protection AG, 4002 Basel, Switzerland; 3Institut of Organic Chemistry, University of Zurich, Winterthurerstrasse 107, CH-8057 Zurich, Switzerland
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Accepted 9 April 1998.
Recognition by rice plants (Oryza sativa) of the nonhost pathogen Pseudomonas syringae pv. syringae leads to an active response ultimately resulting in local acquired resistance against the rice blast fungus Pyricularia oryzae. An observable aspect of this defense response is the increased abundance of a set of transcripts. The accumulation of one of these transcripts, Pir7b, was dependent on the function of the bacterial lemA gene, which encodes part of a two-component regulatory system. This suggested that the lemA regulatory system controlled the production of an elicitor of Pir7b transcript accumulation. This elicitor, which we name syringolin, was purified to homogeneity and its structure was elucidated. Syringolin is a novel and unusual secreted peptide consisting of a 12-membered ring formed by the two non-proteinogenic amino acids 5-methyl-4-amino-2-hexenoic acid and 3,4-dehydrolysine. The α-amino group of the latter is connected by a peptide bond to a valine that in turn is linked to a second valine via a urea moiety. Application of syringolin onto rice leaves elicited the accumulation of Pir7b as well as of other defense-related transcripts and induced resistance toward P. oryzae. Thus, syringolin is one of several determinants by which rice plants can perceive the nonhost pathogen P. syringae pv. syringae.
© 1998 The American Phytopathological Society