Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2001
Publication Date: 9/30/2001
Citation: Yocum, G.D. 2001. Differential expression of two HSP70 transcripts in response to cold shock,thermoperiod, and adult diapause in the Colorado potato beetle. Journal of Insect Physiology. 47(10):1139-1145. Interpretive Summary: A significant component of the production cost of beneficial insects is their short shelf life. Developing means to store insects until they are needed will greatly decrease their cost and increase their economic appeal to producers. Determining an insect's ideal storage conditions would be greatly facilitated by identifying molecular markers (genes) that predict the insect's optimal long term survival at low temperatures and its post-storage reproductive fitness. Two candidate markers were identified using the Colorado potato beetle as a model system. The effect of development and past temperature treatments upon the expression of these markers during low temperature exposure was examined. These molecular markers show promise as aids in developing new storage techniques for beneficial insects.
Technical Abstract: Partial clones for two members of Leptinotarsa decemlineata inducible 70 kDa heat shock protein family (LdHSP70A and B) were developed using RT-PCR. LdHSP70A, but not LdHSP70B, was upregulated during adult diapause. The ability of L. decemlineata to express these two genes in response to subzero temperatures depended on diapause status and thermal history. Nondiapausing beetles expressed only trace amounts of LdHSP70B during recovery from a cold shock, whereas diapausing beetles expressed high levels of both LdHSP70A and B. Chilling diapausing beetles increased the rate at which both LdHSP70A and B were expressed following a cold shock at -10 deg. C. Following cold shock at -10 deg. C, LdHSP70B expression peaked after 3 h at 15 deg. C for chilled diapausing individuals, decreasing to near background levels by the 6th hour. In contrast, nonchilled diapausing beetles expressed their highest level of LdHSP70B only after 6 h at 15 deg. C. Diapausing beetles exposed to a thermoperiod with a mean temperature of either 0 or -2.5 deg. C expressed significantly higher levels of both LdHSP70A and B than beetles exposed to constant 0 or -2.5 deg. C. These results clearly demonstrate that the expression of LdHSP70A and B are regulated by diapause status and environmental conditioning.