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Publikationen - Molekulare Signalverarbeitung

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Publikation

Vörös, K.; Feussner, I.; Kühn, H.; Lee, J.; Graner, A.; Löbler, M.; Parthier, B.; Wasternack, C.; Characterization of a methyljasmonate-inducible lipoxygenase from barley (Hordeum vulgare cv. Salome) leaves Eur. J. Biochem. 251, 36-44, (1998) DOI: 10.1046/j.1432-1327.1998.2510036.x

We found three methyl jasmonate−induced lipoxygenases with molecular masses of 92 kDa, 98 kDa, and 100 kDa (LOX‐92, ‐98 and ‐100) [Feussner, I., Hause, B., Vörös, K., Parthier, B. & Wasternack, C. (1995) Plant J. 7 , 949−957]. At least two of them (LOX‐92 and LOX‐100), were shown to be localized within chloroplasts of barley leaves. Here, we describe the isolation of a cDNA (3073 bp) coding for LOX‐100, a protein of 936 amino acid residues and a molecular mass of 106 kDa. By sequence comparison this lipoxygenase could be identified as LOX2‐type lipoxygenase and was therefore designated LOX2 : Hv : 1 . The recombinant lipoxygenase was expressed in Escherichia coli and characterized as linoleate 13‐LOX and arachidonate 15‐LOX, respectively. The enzyme exhibited a pH optimum around pH 7.0 and a moderate substrate preference for linoleic acid. The gene was transiently expressed after exogenous application of jasmonic acid methyl ester with a maximum between 12 h and 18 h. Its expression was not affected by exogenous application of abscisic acid. Also a rise of endogenous jasmonic acid resulting from sorbitol stress did not induce LOX2 : Hv : 1 , suggesting a separate signalling pathway compared with other jasmonate‐induced proteins of barley. The properties of LOX2 : Hv : 1 are discussed in relation to its possible involvement in jasmonic acid biosynthesis and other LOX forms of barley identified so far.
Publikation

Ward, J. L.; Gaskin, P.; Beale, M. H.; Sessions, R.; Koda, Y.; Wasternack, C.; Molecular modelling, synthesis and biological activity of methyl 3-methyljasmonate and related derivatives Tetrahedron 53, 8181-8194, (1997) DOI: 10.1016/S0040-4020(97)00485-7

Methyl 3-methyljasmonate was synthesised from methyl jasmonate via methyl 3,7-dehydrojasmonate. Molecular modelling predicted an increase in the proportion of cis-orientated side-chains for equilibrated 3-methyl-substituted jasmonate. The synthetic 3-methyljasmonate was shown by gc-ms analysis to equilibrate to a 2:1 ratio of isomers, which appeared from the NMR spectra to comprise mainly the cis-isomer. Surprisingly, both 3,7-dehydro- and 3-methyl-derivatives were inactive in four well established jasmonate bioassays. Methyl-2-methyljasmonate was synthesised and also found to be inactive. Methyl 4,5-dehydrojasmonate was prepared, via the 5-diazo derivative. Both of these compounds have low activity. Our results are discussed with reference to previous knowledge of jasmonate structure-activity relationships and indicate that there are stringent steric demands in jasmonate-receptor interactions.
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