title: Adaptive evolution of the chrysanthemyl diphosphate synthase gene involved in irregular monoterpene metabolism.
abstract: BACKGROUND
  Chrysanthemyl diphosphate synthase (CDS) is a key enzyme in biosynthetic pathways producing pyrethrins and irregular monoterpenes. These compounds are confined to plants of the tribe Anthemideae of the Asteraceae, and play an important role in defending the plants against herbivorous insects. It has been proposed that the CDS genes arose from duplication of the farnesyl diphosphate synthase (FDS) gene and have different function from FDSs. However, the duplication time toward the origin of CDS and the evolutionary force behind the functional divergence of the CDS gene are still unknown.
  
  
  RESULTS
  Two duplication events were detected in the evolutionary history of the FDS gene family in the Asteraceae, and the second duplication led to the origin of CDS. CDS occurred after the divergence of the tribe Mutisieae from other tribes of Asteraceae but before the birth of the Anthemideae tribe. After its origin, CDS accumulated four mutations in sites homologous to the substrate-binding and catalysis sites of FDS. Of these, two sites were involved in the binding of the nucleophilic substrate isopentenyl diphosphate in FDS. Maximum likelihood analyses showed that some sites in CDS were under positive selection and were scattered throughout primary sequences, whereas in the three-dimensional structure model they clustered in the large central cavity.
  
  
  CONCLUSIONS
  Positive selection associated with gene duplication played a major role in the evolution of CDS.
authors.affiliation: College of Life Sciences, Peking University, Beijing 100871, China.
authors.forename: Ping-Li
authors.initials: PL
authors.lastname: Liu
authors.forename: Jun-Nan
authors.initials: JN
authors.lastname: Wan
authors.forename: Yan-Ping
authors.initials: YP
authors.lastname: Guo
authors.forename: Song
authors.initials: S
authors.lastname: Ge
authors.forename: Guang-Yuan
authors.initials: GY
authors.lastname: Rao
mesh_terms: D000595:Amino Acid Sequence; D019659:Asteraceae / Q000201:enzymology; D019143:Evolution, Molecular; D051231:Farnesyltranstransferase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020440:Gene Duplication; D051228:Geranyltranstransferase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D039821:Monoterpenes / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D039821:Monoterpenes; D051228:Geranyltranstransferase; D051231:Farnesyltranstransferase