樟科植物萜类化合物多样性形成机制

Lineage-specific terpenoids appear and enrichment during the evolution of green plants are often believed to play a role in the ecological interactions. Species-specific gene clusters in plants have provided new perspectives on the evolution of secondary metabolism. Lauraceae is an important economic and ecological tree family, with members of the family having considerable value because they are rich in monoterpenes. However, the gene cluster responsible for the biosynthesis of monoterpenes have yet to be elucidated. Here, a Lauraceae-specific citral gene cluster (CGC) was identified and investigated using a multifaceted approach combining phylogenetic, collinearity, biochemical analyses. The CGC comprises MYB44 as a regulator and two alcohol dehydrogenases (ADHs) as the modified enzyme, which is derived from species-specific tandem and proximal duplication. The divergency of ADHs enzyme activity and substrate has led to the fruit of Litsea cubeba, a core Lauraceae species, containing more than 80% of citral. In addition, MYB44 negatively regulated citral biosynthesis by directly binding to the ADHs promoters. Aggregation of specific citral biosynthetic pathways suggests they may form the basis of important characteristics that enhance adaptability. Findings from this study provide new insights into the evolution and regulation mechanism of plant terpene biosynthesis.