Clock gene sequence and expression in the overwintering diapause of the mosquito, Culex pipiens

Over the past several decades a great deal of work has been done to determine roles of certain clock genes, especially period and timeless, in driving daily circadian rhythms. However implicating these same genes in the generation of a photoperiodic response has proven difficult. To determine whether period and timeless play a role in initiating the overwintering diapause of female Culex pipiens mosquitoes, we first obtained full length sequences of these genes. We then compared C. pipiens period and timeless sequences to those of a close relative, Culex quinquefasciatus, which does not enter an ovarian diapause. Additionally, we measured expression of period and timeless over a 24 hour period in adult C. pipiens mosquitoes that were reared under diapausing conditions (short day 18¢ªC), or non-diapausing conditions (long day at 25 or 18¢ªC). Gene expression in diapausing mosquitoes was measured 1 week (early) and 1 month after eclosion (late), and after diapause had been broken, while non-diapausing mosquitoes were sampled one week after adult emergence.