A 1962 bp cDNA clone of 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (purH) was isolated from diapausing adults of Leptinotarsa decemlineata using RT-PCR and 3' and 5'-RACE. The probe generated from this clone hybridized to a transcript approximately 1960 bp in length on northern blots. The clone encodes for a deduced protein 594 amino acids in length with 73% identity, 83% similarity to purH from Drosophila melanogaster. Northern blot (total RNA) analysis determined that L. decemlineata purH (LdpurH) was downregulated in diapausing beetles stored at 10°C. Developmental studies revealed that LdpurH is expressed at nearly constant high levels in both nondiapausing and prediapause adults. LdpurH expression during the first 20 days of diapause is equivalent to that seen in nondiapausing beetles, after which expression decreases. Exposing 70 day old diapausing beetles to 20°C for 24 h induced an increase in expression of purH indicating that purH is regulated by temperature in diapausing/overwintering beetles.
Adults of Colorado potato beetle Leptinotarsa decemlineata are very active at room temperature, and their almost continuous struggling in the respirometer prevents the measurements of the patterns of gas exchange, body movements and heartbeat. The tonic immobility of beetles was evoked by light flashes and by shaking as external stimuli. The immediate reaction to these stimuli was the reflexive closing of the spiracles and the cessation of CO2 release for some minutes, which was followed by a large burst of this gas. The state of the evoked tonic immobility did not influence heartbeat and abdominal pulsations, but the periodically -occurring abdominal-thoracic pumping movements stopped for 2-5 minutes. During the periods of pumping ventilation the metabolic rate was increased about two times.The state of tonic immobility evoked by light flashes lasted 2-6 minutes, but when shaking was applied as a stimulus complete immobility was about two times longer.