Elucidation of the biochemical pathway of 2-phenylethanol from shikimic acid using isolated protoplasts of rose flowers

The isolated protoplasts of rose flowers were used to investigate the metabolic pathway in rose flower leading from shikimic acid or l-phenylalanine (l-Phe) to 2-phenylethanol (2PE), a dominant volatile compound in hybrid roses such as Rosa damascena Mill., R. ‘Hoh-Jun’, and R. ‘Yves Piaget’. Deuterium-labeled l-Phe ([2H8]l-Phe) was supplied to the protoplasts isolated from R. ‘Yves Piaget’ petals. The volatile end products ([2Hn]-2PE, n=6–8) and their related intermediates ([2Hn]phenylacetaldehyde, n=6–8) were detected in the protoplasts by gas chromatography–mass spectrometry (GC–MS). In addition, we chemically synthesized [2,3,4,5,6-13C5]shikimic acid, a new stable isotopomer, to investigate the formation of 2PE from shikimic acid by GC–MS and nuclear magnetic resonance. We proposed the hypothetical biochemical pathway of 2PE from shikimic acid via chorismic acid, l-Phe, and phenylacetaldehyde. This protoplast system facilitates findings of metabolic intermediates and simplifies the complex branching biosynthetic pathways of floral scents to distinct individual events.