Early biosynthetic pathway to abscisic acid in Cercospora cruenta

Article abstract of DOI:10.1271/bbb.64.2075

A new biosynthetic intermediate of ABA, (2Z,4E)-γ-ionylideneacetaldehyde, was isolated from young mycelia of Cercospora cruenta. Under an ¹⁸O₂ atmosphere, an oxygen atom of this endogenous aldehyde was exclusively labeled. Similarly, three ¹⁸O atoms were incorporated into the ABA molecule recovered after prolonged incubation; selectively labeled were one of the carboxyl oxygen atoms and the two on the ring portion of ABA. A feeding experiment with [1-¹³C]glucose proved the exclusive operation of the mevalonate pathway for the formation of both ABA and β-carotene. These results suggest that (2Z,4E)-γ-ionylideneacetaldehyde can be a key ABA biosynthetic intermediate formed by the oxidative cleavage of a carotenoid precursor.