As mentioned above, jasmonic acid is a crucial plant signalling molecule that orchestrates plant defense responses upon attack by necrotrophic pathogens or herbivores. Recent breakthrough papers by have shown that the F-box protein COI1 is directly activated by the JA conjugate JA-isoleucine (Thines et al., 2007 Nature 448(7154):661-665; Chini et al. 2007 Nature 448(7154):666-671.
Activated COI1 degrades repressors of JA signalling, called JAZ proteins. In addition, the bacterial toxin coronatine, which is synthesized by virulent Pseudomonas strains, promotes the COI1-mediated degradation of JAZ proteins. We have become interested in the molecular mechanism of gene induction by jasmonic acid or coronatine when studying the regulation of two terpene synthases. Terpenes are involved in the so called indirect defense response. In this context, they are emitted upon herbivore attack in order to attract their enemies. Depending on the kind of stress, plants can emit different volatiles, thus having the capacity to communicate to their environment. We have found that Arabidopsis activates expression of two terpene synthesis genes upon infection with the nectrotrophic fungus Botrytis cinerea, whereas only one terpene is emitted after feeding with larvae of Plutella xylostella. During our efforts to analyze the molecular basis for the differential expression of both terpene synthesases, we have found that JA and COI1 are essential for the expression of both genes. However, JA or JA-Ile cannot induce one or the other gene, whereas coronatine is very efficient. Our aim is to figure out the molecular basis for the different efficicies of JA-Ile versus coronatine

PhD students: Katrin Gärtner (2004-2008)

Publications: Herde et al. 2008