PHLOEM MOBILITY OF XENOBIOTICS .6. A PHLOEM-MOBILE PRO-NEMATICIDE BASED ON OXAMYL EXHIBITING ROOT-SPECIFIC ACTIVATION IN TRANSGENIC TOBACCO

Phloem mobility is a desirable attribute for pesticides in many applic ations, and the physicochemical properties necessary for phloem mobili ty are now well understood. However, attempts to derivatize pesticides to make them phloem mobile are often frustrated by a concomitant loss of activity. This study describes a phloem-mobile pro-nematicide, a h ydroxymethyloxamyl glucuronide (JR522) coupled with an in-situ activat ion mechanism in transgenic tobacco expressing Escherichia coli beta-g lucuronidase in its root tips. When applied foliarly to the transgenic tobacco, JR522 and its methyl ester (JM775) showed greater nematicida l activity than oxamyl against root-knot nematodes. This example of co mbining pro-pesticide chemistry with crop genetic engineering for site -specific activation provides a model system for demonstrating how to circumvent the often mutual exclusivity of phloem mobility and pestici dal activity. Additional advantages of this scheme include the potenti al mammalian safety of the pro-pesticide, as exhibited by JR522 in thi s study, and a high degree of site-specific release of xenobiotics in plants.