Cold tolerance and seasonal gene expression in Dendroctonus ponderosae.

Several aspects pertaining to quantification of seasonal Dendroctonus ponderosae gene expression, specifically, obtaining measures of inset RNA integrity and selection of stable endogenous controls are discussed. mRNA transcript levels indicate glycerol production in D. ponderosae occurs through both glycogenolytic, gluconeogenic and potentially glyceroneogenic pathways, but not from metabolism of lipids. A two-week lag period between fall glycogen phosphorylase and phosphoenolpyruvate carboxykinase transcript up-regulation indicates gluconeogenesis may serve as a secondary glycerol-production process, subsequent to the potential exhaustion of the primary glycogenolytic source a successive one-two punch of glycerol production. Glycerol kinase is found to be present within D. ponderosae and its mRNA transcript levels increased in the autumn, along with those of triosephosphate isomerase and glycerol-3-phosphate dehydrogenase, suggesting that glycerol is produced from dihydroxyacetone phosphate intermediate. Constant alcohol dehydrogenase transcript levels indicates that a glyceraldehyde-3-phosphate intermediate is not involved in production of glycerol in D. ponderosae. --P. ii.