title: Forest tent caterpillars (Malacosoma disstria) induce local and systemic diurnal emissions of terpenoid volatiles in hybrid poplar (Populus trichocarpa x deltoides): cDNA cloning, functional characterization, and patterns of gene expression of (-)-germacrene D synthase, PtdTPS1.
abstract: Feeding forest tent caterpillars (FTCs) induced local and systemic diurnal emissions of (-)-germacrene D, along with (E)-beta-ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), benzene cyanide, and (E,E)-alpha-farnesene, from leaves of hybrid poplar. FTC feeding induced substantially higher levels of volatiles in local and systemic leaves than did mechanical wounding. A full-length poplar sesquiterpene synthase cDNA (PtdTPS1) was isolated and functionally identified as (-)-germacrene D synthase. Expression of PtdTPS1, expression of genes of early, intermediate and late steps in terpenoid biosynthesis, and expression of a lipoxygenase gene (PtdLOX1) were analyzed in local FTC-infested and systemic leaves. Transcript levels of PtdTPS1 and PtdLOX1 were strongly increased in response to herbivory. PtdTPS1 was also induced by mechanical wounding or by methyl jasmonate (MeJA) treatment. FTC feeding did not affect transcript levels of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR), and isoprene synthase (IPS). Two other TPS genes, PtdTPS2 and PtTPS3, and farnesyl diphosphate synthase were only very transiently induced. These results illustrate differential expression of terpenoid pathway genes in response to insect feeding and a key function of (-)-germacrene D synthase PtdTPS1 for herbivore-induced local and systemic volatile emissions in hybrid poplar. FTC-induced transcripts of PtdTPS1 followed diurnal rhythm. Spatial patterns of FTC-induced PtdTPS1 transcript accumulation revealed acropetal but not basipetal direction of the systemic response. Implications for tritrophic poplar-FTC-predator/parasitoid interactions are discussed.
authors.affiliation: Biotechnology Laboratory, University of British Columbia, 6174 University Boulevard, Vancouver, BC, Canada V6T 1Z3.
authors.forename: Gen-Ichiro
authors.initials: G
authors.lastname: Arimura
authors.forename: Dezene P W
authors.initials: DP
authors.lastname: Huber
authors.forename: Jörg
authors.initials: J
authors.lastname: Bohlmann
mesh_terms: D000085:Acetates / Q000494:pharmacology; D019883:Alkyl and Aryl Transferases / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D019755:Carbon-Carbon Lyases / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D003517:Cyclopentanes / Q000494:pharmacology; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006790:Host-Parasite Interactions; D007113:Immunity, Innate / Q000235:genetics; D007915:Lepidoptera / Q000254:growth & development*; D008969:Molecular Sequence Data; D054883:Oxylipins; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics / Q000469:parasitology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D032107:Populus / Q000737:chemistry / Q000235:genetics* / Q000469:parasitology; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D045788:Sesquiterpenes, Germacrane / Q000096:biosynthesis; D013314:Stress, Mechanical; D013729:Terpenes / Q000378:metabolism*; D014835:Volatilization
chemical_list: D000085:Acetates; D003517:Cyclopentanes; D018076:DNA, Complementary; D054883:Oxylipins; D010940:Plant Proteins; D045788:Sesquiterpenes, Germacrane; D013729:Terpenes; C072239:methyl jasmonate; D019883:Alkyl and Aryl Transferases; C470416:germacrene D synthase; C093854:isoprene synthase; D019755:Carbon-Carbon Lyases; C051130:trichodiene synthetase