Propaquizafop absorption, translocation, metabolism, and effect on acetyl-CoA carboxylase isoforms in chickpea (Cicer arietinum L.)

Propaquizafop absorption, translocation. metabolism, and effects on acetyl- CoA carboxylase (ACCase) isoforms were examined in chickpea (Cicer arientin um L.). Maximum foliar absorption of propaquizafop. approximately 35% of re covered herbicide, occurred 48 h after treatment. Of the absorbed propaquiz afop, approximately 30% was rapidly metabolized to the acid form followed b y a slow conversion of the acid to a polar metabolite. Approximately 4% of foliar-applied [C-14]propaquizafop was translocated from the treated leafle ts within 72 h after application. Chloroplast stromal and cytosolic fractio ns were isolated from chickpea leaves. Proteins from both fractions were se parated by SDS-PAGE and probed with avidin-alkaline phosphatase to detect b iotinylated polypeptides. The cytosolic fraction contained a multifunctiona l ACCase as indicated by the presence of a biotinylated polypeptide of 200 kDa. The chloroplast stromal fraction contained the 36-kDa biotinylated sub unit of the multi-subunit ACCase and a 200-kDa biotinylated protein which s uggested the presence of a plastid-localized multifunctional ACCase. Pretre ating isolated chloroplasts with thermolysin prior to lysis did not reduce the presence of the 200-kDa biotinylated protein. ACCase activity in both c ytosolic and stromal fractions exhibited a high level of tolerance to propa quizafop acid and other graminicides. Total ACCase activity in the chickpea chloroplast stroma fraction appears to be composed of activities contribut ed by both multisubunit and multifunctional ACCases. (C) 1999 Academic Pres s.