Allene Oxide Synthase and Allene Oxide Cyclase, Enzymes of the Jasmonic Acid Pathway, Localized in Glycine max Tissues

Because jasmonic acid regulates a number of processes, including the expression of vegetative storage proteins in soybean (Glycine max L.) leaves, the relative activity of a specific portion of the jasmonic acid biosynthetic pathway in soybean tissues was examined. Allene oxide synthase and allene oxide cyclase were examined because they constitute a branch point leading specifically from 13(S)-hydroperoxy-9(Z), 11(E), 15(Z)-octadecatrienoic acid to 12-oxo-phytodienoic acid, the precursor of jasmonic acid. From growing plants, seed coats (hila plus testae) of green fruits (38 d post-anthesis) were most active, eliciting about 1.5 times greater activity on a per milligram of protein basis than the next most active tissue, which was the pericarp. Leaves from fruiting plants were only one-seventh as active as seed coats, and activities in both immature cotyledons and embryonic axes were very low. No activity was detected in any part of stored, mature seeds. After 72 h of germination of stored seeds, a small amount of activity, about 4% of that in immature seed coats, was found in the plumule-hypocotyl-root, and no activity was detected in the cotyledons. The high levels of jasmonic acid biosynthetic enzymes in soybean pericarp and seed coat suggest a role for jasmonic acid in the transfer of assimilate to seeds.