FIG. 6.

Postulated biosynthetic pathway of ABA in C. pini-densiflorae (late steps, modified from a method described previously by Okamoto et al. [34]). Bold lines indicate the major route. Intermediates identified are α-ionylideneacetic acid (3), 4′-S-OH-α-ionylideneethanol (4), 1′-OH-α-ionylideneethanol (5), 4′-R-OH-α-ionylideneacetic acid (6), 4′-S-OH-α-ionylideneacetic acid (7), and 1′-OH-α-ionylideneacetic acid (8). The enzymatic steps possibly catalyzed by BcABA1, BcABA2, and BcABA4 are indicated.