Evolution of flavors and scents.

The world is filled with flavors and scents, which are the result of volatile compounds produced and emitted by plants. These specialized metabolites are the products of specific metabolic pathways. The terpenoid, fatty acid, and phenylpropanoid pathways contribute greatly to production of volatile compounds. Mechanisms that lead to evolution of volatile production in plants include gene duplication and divergence, convergent evolution, repeated evolution, and alteration of gene expression, caused by a number of factors, followed by change in enzyme specificity. Many examples of these processes are now available for three important gene families involved in production of volatile metabolites: the small molecule O-methyltransferases, the acyltransferases, and the terpene synthases. Examples of these processes in these gene families are found in roses, Clarkia breweri, and sweet basil, among others. Finally, evolution of volatile emission will be an exciting field of study for the foreseeable future.