Figure 1.

Proposed biosynthetic pathways leading to some benzenoid compounds in petunia. CoA-dependent, β-oxidative pathway of side chain shortening is shown in blue, whereas CoA-independent, non-β-oxidative pathway is shown in black. Red arrows show CoA-dependent and non-β-oxidative pathway. Solid arrows indicate established biochemical reactions, whereas broken arrows indicate possible steps not yet described. The conversion of cinnamoyl-CoA to benzoyl-CoA has already been described in mammals (Mao et al., 1994). BSMT and SAMT, S-adenosyl-l-Met:benzoic acid/salicylic acid and salicylic acid carboxyl methyltransferase, respectively; BA2H, benzoic acid 2-hydroxylase; BZL, benzoate:CoA ligase; C4H, cinnamic acid-4-hydroxylase; SA GTase, UDP-Glc:salicylic acid glucosyltransferase. Volatile benzenoid/phenylpropanoid-related compounds shown with a yellow background were analyzed in petunia floral scent and in petal tissue. Additionally, the pools of l-Phe and benzoic acid were also evaluated.