Fig. 6 in Lilium floral fragrance: A biochemical and genetic resource for aroma and flavor

Fig. 6. Phenylpropanoid and benzenoid biosynthesis and cultivar emission. Histograms for all panels represent volatiles emitted by proximal tepals in ng * gFW—1 * hr—1 for all cultivars ('Belladonna' – B, 'Conca d'Or' – C, 'Robina' – R, 'Santander' – S, 'Tarrango' – T). Graphic representation of chemical structure, biosynthetic pathway, and histogram of quantitated volatile compounds in which an arrow represents one enzymatic reaction. Phenylpropanoids phenylacetaldehyde (41), phenylethyl alcohol (42), and 2- phenylethyl acetate (43) are synthesized sequentially from phenylalanine (67). Counter, phenylalanine (67) can be converted to (E)-cinnamic acid (68) and imported into the peroxisome which ultimately exports benzyl-CoA (69). This activated benzoyl group is substrate to four different reactions which give rise directly to phenylethyl benzoate (39), benzyl acetate (36), benzyl benzoate (38), and benzyl alcohol (35). Benzyl alcohol (35) is the second precursor to benzyl benzoate (38) synthesis as well as an indirect precursor of benzaldehyde (24), methyl salicylate (37), and methyl benzoate (25) synthesis. Metabolic flow and bottlenecks are evident at different biosynthetic nodes. For instance, all three phenylpropanoids are present in 'Belladonna' indicating enzymatic activity and substrate buildup at the three nodes. A limiting activity of the third node and high activity of the first node results in no phenylacetaldehyde (41) emission, substantial phenylethyl alcohol (42) emission, and minimal 2-phenylethyl acetate (43) as observed in 'Robina'. 'Santander' has the greatest emission of benzyl alcohol (35) and benzaldehyde (24); a buildup due to non-existent methyl salicylate (37), methyl benzoate (25), and benzyl benzoate (38) emission, which is observed in all other cultivars.