EVIDENCE FOR THE INVOLVEMENT OF JASMONATES AND THEIR OCTADECANOID PRECURSORS IN THE TENDRIL COILING RESPONSE OF BRYONIA-DIOICA

The structural requirements of jasmonates to induce tendril coiling in Bryonia dioica were investigated. 9,10-Dihydromethyljasmonate, the 6- hydroxy analogues of methyljasmonate and dihydromethyljasmonate as wel l as 6-desoxyjasmonates were inactive up to 0.1 mM concentration, wher eas methyljasmonate (JAME) was highly active at 5-10 muM (threshold: 1 muM) concentration. All biosynthetic precursors of jasmonic acid (alp ha-linolenic acid, 13-hydroperoxylinolenic acid and 12-oxo-phytodienoi c acid (PDA) tested were biologically active. The methyl ester of PDA (PDAME) was the most active inducer, with relative activities: PDAME> >JAME> >13-hydroperoxylinolenic acid approximately alpha-linolenic aci d. The response to PDAME was also much more rapid than that to JAME. F atty acid analysis of tendril tissue showed the presence of alpha-lino lenic acid in membrane lipids, including plasma membranes. Shortly aft er a touch stimulus, the cellular pool of free alpha-linolenic acid dr ops faster than that of other fatty acids suggesting a preferential re quirement for this fatty acid. Jasmonic acid (JA) is present in leaf a nd tendril extracts of B. dioica, as shown using a highly sensitive an d selective LC-HPLC-ELISA technique based on the monoclonal anti-(-)-J AME antibody JAH1-8B4-2A11[limit of detection < 1 pmol (-)-JAME]. Coil ing elicited with JAME or indole-3-acetic acid proceeded with increase d ethylene evolution. Aminoethoxyvinylglycine inhibited this ethylene formation to below levels of controls without any effect on coiling. C ollectively, our data support the view that touch rapidly initiates in B. dioica tendrils the formation of jasmonates from alpha-linolenic a cid which are released as messengers triggering the coiling response. Specific sites (receptors) for the recognition of jasmonates have to b e postulated in order to explain the high structural selectivity of th e response. The finding that PDAME acts considerably faster and at muc h lower levels than JAME suggests that it either reaches the precise l ocation of jasmonate formation in the cell more easily than JAME itsel f giving rise to high local jasmonate levels or that PDAME is by itsel f an active inducer of tendril coiling.