abstract
Iturin A is the most well studied antifungal cyclic lipopeptide produced by Bacillus species that are
frequently utilized as biological control agents. Iturin A not only shows strong antifungal activity against
phytopathogens but also induces defense response in plants, thereby reducing plant disease severity.
Here we report the defense signaling pathways triggered by iturin A in Arabidopsis salicylic acid (SA) or
jasmonic acid (JA)-insensitive mutants. Iturin A activated the transcription of defense genes PR1 and
PDF1.2 through the SA and JA signaling pathways, respectively. The role of iturin A as an elicitor was
dependent on the cyclization of the seven amino acids and/or the b-hydroxy fatty acid chain. The iturin A
derivative peptide, NH2-(L-Asn)-(D-Tyr)-(D-Asn)-(L-Gln)-(L-Pro)-(D-Asn)-(L-Ser)-COOH, completely
suppressed PR1 and PDF1.2 gene expression in wild Arabidopsis plants. The identification of target
molecules binding to iturin A and its derivative peptide is expected to shed new light on defense
response in plants through the SA and JA signaling pathways.