Linalool: A ubiquitous floral volatile mediating the communication between plants and insects

Terpenoids, one of the most important plant volatiles, mediate the communication between plants and pollinators, herbivores as well as pathogens. Recently, researchers have shown intensive interest in the complicated interactions. Linalool, an acyclic monoterpene, is one of the common flavor-related volatiles across the plant kingdom. In this review, we summarized the biosynthesis and transcriptional regulation of terpenoids, and then focused on the biological function of linalool in plant–insect interactions. We found that flowers emitting linalool as the dominant volatile appeal to broad assemblages of pollinators, while some pollinators typically have strong preferences for these flowers as well. Hereinto, moths and bees are the main pollinators of linalool-dominant flowers. Additionally, linalool produced by plants could defend against insect pests and pathogens. It is noteworthy that the two enantiomers of linalool have distinct functions. (S)-(+)-linalool mainly attracts pollinators, while (R)-(−)-linalool seems to act as insect repellents. Further research on the biofunctional diversity and genetic mechanisms of linalool enantiomers will reveal the complexity of plant survival strategies, and the increasing understanding of the molecular mechanisms underlying their biosynthesis and transcriptional regulation will provide theoretical foundation and practical basis for directional transformation of plants.