Coordinated gene expression for pheromone biosynthesis in the pine engraver beetle, Ips pini (Coleoptera: Scolytidae)
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In several pine bark beetle species, phloem feeding induces aggregation pheromone production to coordinate a mass attack on the host tree. Male pine engraver beetles, Ips pini (Say) (Coleoptera: Scolytidae), produce the monoterpenoid pheromone component ipsdienol de novo via the mevalonate pathway in the anterior midgut upon feeding. To understand how pheromone production is regulated in this tissue, we used quantitative real-time PCR to examine feeding-induced changes in gene expression of seven mevalonate pathway genes: acetoacetyl-coenzyme A thiolase, 3-hydroxy-3-methylglutaryl coenzyme A synthase, 3-hydroxy-3-methylglutaryl coenzyme A reductase, mevalonate 5-diphosphate decarboxylase, isopentenyl-diphosphate isomerase, geranyl-diphosphate synthase (GPPS), and farnesyl-diphosphate synthase (FPPS). In males, expression of all these genes significantly increased upon feeding. In females, the expression of the early mevalonate pathway genes (up to and including the isomerase) increased significantly, but the expression of the later genes (GPPS and FPPS) was unaffected or decreased upon feeding. Thus, feeding coordinately regulates expression of the mevalonate pathway genes necessary for pheromone biosynthesis in male, but not female, midguts. Furthermore, basal mRNA levels were 5- to 41-fold more abundant in male midguts compared to female midguts. This is the first report of coordinated regulation of mevalonate pathway genes in an invertebrate model consistent with their sex-specific role in de novo pheromone biosynthesis.
KeywordsBark Beetle Mevalonate Pathway Pheromone Production Ipsdienol Monoterpenoid
We thank J.C. Bearfield and A. Gilg-Young for sharing unpublished sequence data and designing real-time primers for GPPS, J.C. Bearfield and G.M. Hall for assistance with collecting the beetles, J. Rowe and C. Osborne at the Nevada Genomics Center for assistance with the real-time PCR instrument, and E. Plettner for comments on an earlier version of this manuscript. This work was supported by a Canadian NSERC postdoctoral fellowship to C.I.K., the USDA (2001-35302-11035), the NSF (IBN 0316370), the Nevada Agricultural Experiment Station (publication no. 03031391), the Nevada Biomedical Research Infrastructure Network (P20 RR 16464), and represents research coordinated in part through USDA-CSREES Multistate Research Project W-189. This research was conducted in accordance with the current laws of the USA.
- Birch MC, Light DM, Wood DL, Browne LE, Silverstein RM, Bergot BJ, Ohloff G, West JR, Young JC (1980) Pheromonal attraction and allomonal interruption of Ips pini in California by the two enantiomers of ipsdienol. J Chem Ecol 6:703–717Google Scholar
- Browne LE (1972) An emergence cage and refrigerated collector for wood-boring insects and their associates. J Econ Entomol 65:1499–1501Google Scholar
- Casals N, Buesa C, Piulachs M-D, Cabañó J, Marrero PF, Bellés X, Hegardt FG (1996) Coordinated expression and activity of 3-hydroxy-3-methylglutaryl coenzyme A synthase and reductase in the fat body of Blattela germanica (L.) during vitellogenesis. Insect Biochem Mol Biol 26:837–843CrossRefPubMedGoogle Scholar
- Pureswaran DS, Gries R, Borden JH, Pierce HD Jr (2000) Dynamics of pheromone production and communication in the mountain pine beetle, Dendroctonus ponderosae Hopkins, and the pine engraver, Ips pini (Say) (Coleoptera: Scolytidae). Chemoecology 10:153–168Google Scholar
- Seybold SJ, Quilici DR, Tillman JA, Vanderwel D, Wood DL, Blomquist GJ (1995) De novo biosynthesis of the aggregation pheromone components ipsenol and ipsdienol by the pine bark beetles Ips paraconfusus Lanier and Ips pini (Say) (Coleoptera: Scolytidae). Proc Natl Acad Sci USA 92:8393–8397PubMedGoogle Scholar
- Vité JP, Bakke A, Renwick JAA (1972) Pheromones in Ips (Coleoptera: Scolytidae): occurrence and production. Can Entomol 104:1967–1975Google Scholar
- Wood SL (1982) The bark and ambrosia beetles of north and central America (Coleoptera: Scolytidae), a taxonomic monograph. Brigham Young University, Salt Lake City, Utah, USAGoogle Scholar