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 arientinum L.). Maximum foliar absorption of propaquizafop, approximately 35% of recovered herbicide, occurred 48 h after treatment. Of the absorbed propaquizafop, approximately 30% was rapidly metabolized to the acid form followed by a slow conversion of the acid to a polar metabolite. Approximately 4% of foliar-applied [14C]propaquizafop was translocated from the treated leaflets within 72 h after application. Chloroplast stromal and cytosolic fractions were isolated from chickpea leaves. Proteins from both fractions were separated by SDS-PAGE and probed with avidin-alkaline phosphatase to detect biotinylated polypeptides. The cytosolic fraction contained a multifunctional ACCase as indicated by the presence of a biotinylated polypeptide of 200 kDa. The chloroplast stromal fraction contained the 36-kDa biotinylated subunit of the multi-subunit ACCase and a 200-kDa biotinylated protein which suggested the presence of a plastid-localized multifunctional ACCase. Pretreating isolated chloroplasts with thermolysin prior to lysis did not reduce the presence of the 200-kDa biotinylated protein. ACCase activity in both cytosolic and stromal fractions exhibited a high level of tolerance to propaquizafop acid and other graminicides. Total ACCase activity in the chickpea chloroplast stroma fraction appears to be composed of activities contributed by both multisubunit and multifunctional ACCases.