Publikationen - Molekulare Signalverarbeitung

Jasmonic acid and 66 structurally related compounds were tested to find the structural requirements which induce the expression of jasmonate-responsive genes in barley. An intact cyclopentanone ring as well as a pentenyl side chain exhibiting only minor alterations are necessary for this activity. The (−)-enantiomeric and the (+)-7-iso-enantiomeric structure increase activity of jasmonoyl compounds.

Aspergillus niger is able to hydroxylate the pentenyl side chain of (−)-jasmonic acid (JA) leading to (11S)- (−)-hydroxy-JA/ (11R)- (−)-hydroxy-JA (2:1) and (−)-11,12-didehydro-JA. Methyl (−)-jasmonate (JA-Me) is converted upon hydrolysis. During prolonged cultivation or at non-optimized isolation procedures, the 11-hydroxy- (9Z)-pentenyl side chain may isomerize to (10E)-9-hydroxy- and (9E)-11-hydroxy-compounds by allylic rearrangement. The fungus hydroxylates (±)-9,10-dihydro-JA at position C-11 into 11j-hydroxy-9,10-dihydro-JA. As JA-Me, the methyl dihydro-JA is hydroxylated only upon hydrolysis into the free acid.

The culture filtrate of Fusarium oxysporum f sp matthiolae was inspected on the occurrence of jasmonates and related compounds. Among compounds described for the first time of biological origin are 7-iso-cucurbic acid, (1S,2S)- and (1S,2R)-3-oxo-2-pentylcyclopentane-1-butyric acid, (1S,2S)- and (1S,2R)-3-oxo-2-(2Z-pentenyl)cyclopentane-1-hexanoic acid, (1S,2S)- and (1S,2R)-3-oxo-2-pentylcyclopentane-1-hexanoic acid, (1S,2S)-3-oxo-2-(2Z-pentenyl)cyclopentane-1-octanoic acid, (1S,2S)-3-oxo-2-pentylcyclopentane-1-octanoic acid and N-[9,10-dihydro-7-iso-jasmonoyl]-(S)-isoleucine. The following metabolites were identified for the first time for this fungus: (−)-Jasmonic acid, 9,10-dihydrojasmonic acid and N-[(−)-jasmonoyl-(S)]-isoleucine were major constituents of the culture filtrate, whereas as minor metabolites occurred N-[9,10-dihydrojasmonoyl]-(S)-isoleucine, cucurbic acid and 3-oxo-2-(2Z-pentenyl)cyclopentane-1-butyric acid, 3-oxo-2-(2Z-pentenyl)cyclopentane-1-octanoic acid and 3-oxo-2-pentylcyclopentane-1-octanoic acid. All cyclopentanones found carried a cis- or trans-attached side chain. Didehydro-jasmonates, hydroxylated jasmonates or 12-oxophytodienoic acid could not be detected in the culture filtrate.