Figure 6.

Biosynthesis of Jasmonic Acid and 12-Oxophytodienoate Reductase Enzymatic Activity in Wild-Type and delayed dehiscence1 Plants.

(A) Jasmonic acid biosynthesis pathway (modified from Schaller and Weiler, 1997a; Weiler, 1997). Linolenic acid (18:3) is converted to the cyclic molecule 12-oxophytodienoic acid (OPDA) after three enzymatic steps that occur in the chloroplast. In the third step, allene oxide cyclase produces a specific stereochemical form of OPDA (Schaller and Weiler, 1997b). The cytoplasmic enzyme OPR converts OPDA into 3-oxo-2-(2′-Z-pentenyl)-cyclopentane-1-octanoic acid (OPC-8:0). The generation of jasmonic acid from OPC-8:0 occurs in the peroxisomes after three rounds of β-oxidation.

(B) Absence of OPR enzyme activity in vegetative tissues of delayed dehiscence1. delayed dehiscence1 (dde1) and wild-type (WT) plants at the rosette stage were assayed for 12-oxophytodienoate reductase (OPR) activity. The conversion of OPDA to OPC-8:0 (OPR activity) was assayed by the addition of racemic cis-OPDA or cis-(+)OPDA to crude protein extracts (see Methods). The results are an average of five independent experiments. Error bars represent standard deviation of the mean of all five experiments. ND, not detected.