ON THE ROLE OF OPINES IN PLANTS TRANSFORMED WITH AGROBACTERIUM-RHIZOGENES - TROPANE ALKALOID METABOLISM, INSECT-TOXICITY AND ALLELOPATHIC PROPERTIES

The opines, mannopine and mikimopine, which are formed in roots after transformation with Agrobacterium rhizogenes 15834 and A. rhizogenes MAFF03-01724, were synthesized chemically and their influence on the alkaloid production in root cultures of Hyoscyamus albus was examined. In adventitious root cultures the addition of opines resulted in a rapid alkaloid degradation. Alkaloid content was restored to a <<normal>> level within 5 days. Alkaloid accumulation in hairy roots reacted differently: The addition of mikimopine enhanced alkaloid production whereas the addition of mannopine generally reduced the alkaloid content. Most of the different tropane alkaloids produced by the adventitious and the hairy root cultures were affected in the same way by the addition of the opines. Roots were able to take up exogenously supplied opines. The addition of opines to the culture medium replaced carbon or nitrogen sources of the media to some degree. Mikimopine and mannopine reduced growth of Manduca sexta larvae and had deterrent properties at higher concentrations. In addition, mikimopine showed allelopathic properties and retarded the germination of Lepidium sativum seeds and growth of seedlings. It is speculated that the opines serve both Agrobacteria and the infected plants, supposedly the latter in plant-plant and plant-insect interactions. Thus, Agrobacteria - plant relationships might be considered to be of rather symbiotic than pathogenic nature.