title: Characterization and tissue-specific expression of two lepidopteran farnesyl diphosphate synthase homologs: implications for the biosynthesis of ethyl-substituted juvenile hormones.
abstract: The sesquiterpenoid juvenile hormone (JH) regulates insect development and reproduction. Most insects produce only one chemical form of JH, but the Lepidoptera produce four derivatives featuring ethyl branches. The biogenesis of these JHs requires the synthesis of ethyl-substituted farnesyl diphosphate (FPP) by FPP synthase (FPPS). To determine if there exist more than one lepidopteran FPPS, and whether one FPPS homolog is better adapted for binding the bulkier ethyl-branched substrates/products, we cloned three lepidopteran FPPS cDNAs, two from Choristoneura fumiferana and one from Pseudaletia unipuncta. Amino acid sequence comparisons among these and other eukaryotic FPPSs led to the recognition of two lepidopteran FPPS types. Type-I FPPSs display unique active site substitutions, including several in and near the first aspartate-rich motif, whereas type-II proteins have a more "conventional" catalytic cavity. In a yeast assay, a Drosophila FPPS clone provided full complementation of an FPPS mutation, but lepidopteran FPPS clones of either type yielded only partial complementation, suggesting unusual catalytic features and/or requirements of these enzymes. Although a structural analysis of lepidopteran FPPS active sites suggested that type-I enzymes are better suited than type-II for generating ethyl-substituted products, a quantitative real-time PCR assessment of their relative abundance in insect tissues indicated that type-I expression is ubiquitous whereas that of type-II is essentially confined to the JH-producing glands, where its transcripts are approximately 20 times more abundant than those of type-I. These results suggest that type-II FPPS plays a leading role in lepidopteran JH biosynthesis in spite of its apparently more conventional catalytic cavity.
authors.affiliation: Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, Québec City, Québec G1V 4C7, Canada. michel.cusson@nrcan.gc.ca
authors.forename: Michel
authors.initials: M
authors.lastname: Cusson
authors.forename: Catherine
authors.initials: C
authors.lastname: Béliveau
authors.forename: Stephanie E
authors.initials: SE
authors.lastname: Sen
authors.forename: Sophie
authors.initials: S
authors.lastname: Vandermoten
authors.forename: Robert G
authors.initials: RG
authors.lastname: Rutledge
authors.forename: Don
authors.initials: D
authors.lastname: Stewart
authors.forename: Frédéric
authors.initials: F
authors.lastname: Francis
authors.forename: Eric
authors.initials: E
authors.lastname: Haubruge
authors.forename: Peter
authors.initials: P
authors.lastname: Rehse
authors.forename: David J
authors.initials: DJ
authors.lastname: Huggins
authors.forename: Ashley P G
authors.initials: AP
authors.lastname: Dowling
authors.forename: Guy H
authors.initials: GH
authors.lastname: Grant
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D018076:DNA, Complementary; D004330:Drosophila / Q000737:chemistry / Q000201:enzymology; D051228:Geranyltranstransferase / Q000737:chemistry*; D007605:Juvenile Hormones / Q000096:biosynthesis / Q000737:chemistry*; D007915:Lepidoptera / Q000737:chemistry / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D011106:Polyisoprenyl Phosphates / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D016415:Sequence Alignment; D012717:Sesquiterpenes; D013045:Species Specificity
chemical_list: D018076:DNA, Complementary; D007605:Juvenile Hormones; D011106:Polyisoprenyl Phosphates; D012717:Sesquiterpenes; C004808:farnesyl pyrophosphate; D051228:Geranyltranstransferase