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Jasmonates are phytohormones known as signals in plant responses to biotic and abiotic stress and in developmental processes. The goal of the research group was the analysis of mode action of jasmonates.

Transgenic approaches were used to switch on or off biosynthesis of jasmonic acid and its metabolites such as 12-hydroxyjasmonic acid. Such modulation of jasmonate levels in planta was performed in a constitutive, induced or cell type specific manner. Mainly tomato and Arabidopsis were used. In both species a mechanistic analysis was studied of mode of action of jasmonates as signals in plant defence reaction and plant development. Most of the experimental work of the research group was finished in 2008.

Jasmonic acid (JA) is synthesized from α-linolenic acid of chloroplast membranes. The three chloroplast-located enzymes 13-lipoxygenase (13-LOX), 13-allene oxide synthase (13-AOS) and allene oxide cyclase (AOC) catalyze the first half of JA biosynthesis up to the intermediate product cis-(+)-12-oxophytodienoic acid (OPDA). The AOC product OPDA contains the enantiomeric structure of the naturally occurring (+)-7-iso-JA thereby indicating the role of AOC in JA biosynthesis.

The second half of JA biosynthesis takes place in peroxisomes, if OPDA or its CoA ester is transported. Within peroxisomes the cyclopentenone ring is reduced and subsequently acting enzymes of the fatty acid β-oxidation machinery catalyze a shortening of the carboxylic acid side chain of OPDA.

In the last couple of years the following questions were addressed using tomato and Arabidopsis:

• analysis of the AOC gene family in stress responses and development of A. thaliana
• the role of AOC and tissue-specific JA generation in the wound response of tomato
• the role of JA and oxylipins in embryo development of tomato
• the regulation of JA biosynthesis by light in A. thaliana
• Metabolism of JA by hydroxylation, sulfation and glycosylation and its role in JA signal transduction

Numerous cooperations with groups in Germany and abroad were performed in respect to analyses of jasmonates and oxylipins (cf publication list … link). The following aspects were covered in 2008/2009:

• Stress- and JA- induced lectines of tobacco (E. van Damme, Gent, Belgium)
• modulation of JA levels in tobacco by expression of single chain antibodies raised against jasmonates (U. Conrad, IPK, Gatersleben)
• role of 4-Coumarate: CoA-ligase-like enzymes in JA biosynthesis (E. Kombrink, MPI, Cologne)
• role of OPDA and JA in transcriptional and metabolic alteration of C- and N-metabolism of pea embryos with decreased ADP-glucose-pyrophosphorylase level (H. Weber, IPK, Gatersleben)
• cooperative action of JA and salicylate during basal thermotolerance of A. thaliana (L. Mur, Aberystwyth, England; S. M. Clarke, Dunedin, New Zealand)
• role of APS kinase gene family of A. thaliana during sulfation of 12-hydroxyjasmonate (S. Kopriva, Norwich, England)
• use of plant glutaminyl cyclases (QCs) for development of QC inhibitors (industrial cooperation with Probiodrug AG, Halle)
• identification of (+)-7-iso-jasmonoyl-L-isolencine as endogenous bioactive ligand of the JA receptor. This important work was a cooperation between the groups of R. Solano (Madrid, Spain), M. Hamberg (Stockholm, Sweden) and Halle. The group in Halle attributed mainly by experience in chemistry of JA and JA amino acid conjugates.

The experimental activities of the research groups were mostly finished in 2008 due to retirement of several group members and the group leader. The former department of Natural Product Biotechnology is now renamed as Molecular Signal Processing and is leaded by Professor Steffen Abel (formerly UC Davis, California, USA). The scientific and technical know-how of the research group “Mode of action of jasmonates” in respect to analysis of jasmonates is transferred so far to the research group “Jasmonate Function & Mycorrhiza” (Bettina Hause) within the Department of Secondary Metalism.

Claus Wasternack will be active as guest of the IPB till 2010, to fullfil tasks as referee, to perform examinations of Diploma students and to finish publications. In this framework cooperative research work will be finished with J. Turner (UEA, Norwich, England), R. Fluhr (Weizmann-Institute, Rehovot, Israel), Ch. Li (Academy of Sciences, Beijing, China), A. Schaller (University, Stuttgart-Hohenheim, Germany), I. Feussner (University of Goettingen, Germany), R. Deeken (University of Wuerzburg, Germany) and B. Hause (IPB, Halle).