Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2008
Publication Date: 1/1/2009
Publication URL: http://ddr.nal.usda.gov/bitstream/10113/23080/1/IND44152776.pdf
Citation: Yocum, G.D., Rinehart, J.P., Chirumamilla, A., Larson, M.L. 2009. Characterization of Gene Expression Patterns During the Initiation and Maintenance Phases of Diapause in the Colorado Potato Beetle, Leptinotarsa decemlineata. Journal of Insect Physiology. 55(1):32-39. Interpretive Summary: The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is the major defoliator of potato and also feeds on tomato and eggplant. The CPB is endemic in most of the potato growing regions worldwide. The plasticity of the CPB’s diapause response played a key role in its range expansion. Dormancy in the form of diapause or quiescence enables insects to survive and synchronize their life cycles to the abiotic and biotic factors needed for development and reproduction. Dormancy in the CPB can take the forms of diapausing for a single winter, prolonged diapause lasting for more than one winter, repeated diapause, i.e., single winter diapauses interrupted by reproduction cycles and summer diapause (quiescence). In addition to the various forms of diapause, there is a considerable degree of intra- and inter-population variation in the phenotypic expression of diapause. In order to monitor and model CPB phenology under field conditions and develop an understanding of the mechanism(s) involved in this variation, reliable biomarkers are needed. Here we study the prediapause phase: the period when the environmental signals inducing the diapause program are received and processed, physiological and behavioral changes occur that lead to the selection of appropriate diapausing sites, and metabolic reserves are stockpiled. The underlying molecular aspects of these critical processes are still undefined. The aim of this investigation is twofold: 1) Isolate differentially-regulated-diapause genes; 2) From the pool of differentially-regulated-diapause genes, identify potential biomarkers for future field studies.
Technical Abstract: Using differential display, 55 putative, diapause-regulated transcripts were isolated from the Colorado potato beetle, Leptinotarsa decemlineata (Say). The insert sizes of the clones ranged from 114 to 795 bp. Fourteen of the transcripts were confirmed by northern blot analysis to be diapause regulated. Based on Blast search results the diapause-regulated transcripts were assigned putative identities and placed into four broad categories of proteins: unknown function, defensive, structural/glycine-rich, and digestive. The transcripts were highly expressed for the first 13 to 15 days postemergence in prediapausing adults and were then substantially down-regulated in diapausing beetles. The diapause-down-regulated transcripts were also highly expressed for the first seven days postemergence in nondiapausing adults and their expression became more variable on day 9 or 11 in most individuals examined. The glycine-rich protein transcripts were all down-regulated by day 11 in the nondiapausing adults. A comparison of the transcript expression patterns in prediapausing and nondiapausing adults showed that expression of the glycine-rich transcripts persisted for approximately four days longer in the prediapausing beetles.