Biosynthesis of abscisic acid from farnesol derivatives in Cercospora rosicola

(E,E)?1?¹⁴C]Farnesyl phosphate and (E,E)?1?¹⁴C]farnesyl pyrophosphate were both converted to abscisic acid by Cercospora rosicola resuspensions. (E,E)?1?¹⁴C]Farnesol, (E,Z)?1?¹⁴C]farnesol, (E,Z)?1?¹⁴C]farnesyl pyrophosphate, (E,E)?1?¹⁴C]farnesic acid, and (E,Z)?1?¹⁴C]farnesic acid were not converted to abscisic acid by the fungus. These findings provide information on the sequence of the reactions involved in converting farnesyl pyrophosphate to abscisic acid. Specifically, they suggest that the transformations involving the three terminal carbons in the side chain occur after one or more changes elsewhere in the molecule.