Increasing Temperature Changes Flux into Multiple Biosynthetic Pathways for 2-Phenylethanol in Model Systems of Tea (Camellia sinensis) and Other Plants

2-Phenylethanol (2PE) is a representative aromatic aroma compound in tea (Camellia sinensis) leaves. However, its formation in tea remains unexplored. In our study, feeding experiments of [²H₈]L-phenylalanine (Phe), [²H₅]phenylpyruvic acid (PPA), or (E/Z)-phenylacetaldoxime (PAOx) showed that three biosynthesis pathways for 2PE derived from L-Phe occurred in tea leaves, namely, pathway I (via phenylacetaldehyde (PAld)), pathway II (via PPA and PAld), and pathway III (via (E/Z)-PAOx and PAld). Furthermore, increasing temperature resulted in increased flux into the pathway for 2PE from L-Phe via PPA and PAld. In addition, tomato fruits and petunia flowers also contained the 2PE biosynthetic pathway from L-Phe via PPA and PAld and increasing temperatures led to increased flux into this pathway, suggesting that such a phenomenon might be common among most plants containing 2PE. This represents a characteristic example of changes in flux into the biosynthesis pathways of volatile compounds in plants in response to stresses.