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 well as 6-desoxyjasmonates were inactive up to 0.1 mM concentration, whereas methyljasmonate (JAME) was highly active at 5-10 muM (threshold: 1 muM) concentration. All biosynthetic precursors of jasmonic acid (alpha-linolenic acid, 13-hydroperoxylinolenic acid and 12-oxo-phytodienoic 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 acid. The response to PDAME was also much more rapid than that to JAME. Fatty acid analysis of tendril tissue showed the presence of alpha-linolenic acid in membrane lipids, including plasma membranes. Shortly after a touch stimulus, the cellular pool of free alpha-linolenic acid drops faster than that of other fatty acids suggesting a preferential requirement for this fatty acid. Jasmonic acid (JA) is present in leaf and tendril extracts of B. dioica, as shown using a highly sensitive and selective LC-HPLC-ELISA technique based on the monoclonal anti-(-)-JAME antibody JAH1-8B4-2A11[limit of detection < 1 pmol (-)-JAME]. Coiling elicited with JAME or indole-3-acetic acid proceeded with increased ethylene evolution. Aminoethoxyvinylglycine inhibited this ethylene formation to below levels of controls without any effect on coiling. Collectively, our data support the view that touch rapidly initiates in B. dioica tendrils the formation of jasmonates from alpha-linolenic acid which are released as messengers triggering the coiling response. Specific sites (receptors) for the recognition of jasmonates have to be postulated in order to explain the high structural selectivity of the response. The finding that PDAME acts considerably faster and at much lower levels than JAME suggests that it either reaches the precise location of jasmonate formation in the cell more easily than JAME itself giving rise to high local jasmonate levels or that PDAME is by itself an active inducer of tendril coiling.