IMPACT OF CYCLICAL CHANGES IN TEMPERATURE ON CIRCADIAN CLOCK GENES EXPRESSION IN Bombyx BmN CELLS.

The physiology and metabolism of poikilothermic insects are under the control of environmental temperature. Temperature is the primary cue for the circadian rhythm. Reports on the timing mechanisms of temperature in lepidopterans are limited. This study used Bombyx mori BmN ovarian cells to investigate the effect of temperature on expression of the main circadian clock genes in a negative feedback loop. A 37°C, 30-min high-temperature stimulation induced transcription of the circadian clock genes Cry1, Cry2, Per, and Tim. The gene expression profiles showed rhythmic oscillations, with shortened oscillatory periods for Cry1 and altered oscillatory phases for Cry1 and Per. Cyclical increases in temperature of 2°C starting at 26°C, 5°C starting at 20 or 25°C, or 10°C starting at 20°C induced cyclical changes in expression and protein from the four circadian clock genes. Cyclical temperature changes with a difference of 10°C had the most influence. In conclusion, cyclical changes in temperature with differences from 2 to 10°C reset and synchronized the circadian clock of silkworm BmN cells. Transcription of the genes for and protein from Cry2 and Per showed a better reset and synchronization with cyclical temperature changes.