Differential expression of two HSP70 transcripts in response to cold shock, thermoperiod, and adult diapause in the Colorado potato beetle

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 the thermal history of the beetles. Chilling diapausing beetles increased the rate at which both LdHSP70A and B were expressed following a cold shock at −10°C. Following cold shock at −10°C, LdHSP70B expression peaked after 3 h at 15°C for chilled diapausing individuals, decreasing to near background levels by the sixth hour. In contrast, nonchilled diapausing beetles expressed their highest level of LdHSP70B only after 6 h at 15°C. Diapausing beetles exposed to a thermoperiod with a mean temperature of either 0 or −2.5°C expressed significantly higher levels of both LdHSP70A and B than beetles exposed to constant 0 or −2.5°C. These results demonstrate that the expression of LdHSP70A and B is differentially regulated in response to diapause and environmental conditioning.