Expression of spliced variants of period mRNA in the Japanese honeybee Apis cerana japonica

Abstract

We report the expression of two mRNA variants, α and β, of the period (per) gene in honeybees. These have not been found in other insects. The genomic DNA sequence of the per gene in the Japanese honeybee (Apis cerana japonica) showed that the variants are produced by alternative splicing of an intron. Total per mRNA in the brain increased in the dark period and decreased in the light, whereas mRNA of the muscle showed an opposite phase oscillation. No significant rhythmic expression of per mRNA was observed in the compound eye and midgut. The expression ratio of the α and β variants of per mRNA was investigated at zeitgeber times (ZTs) 6 and 18 (the middle of the day and night, respectively) under 12:12 h light–dark (LD) conditions. The per α variant increased in the dark in both organs, whereas expression of the β variant showed an opposite pattern between the organs. The higher total per mRNA expression in muscle in the light period was due to an increase in the β variant. Such expression patterns suggest that there is a functional differentiation between the α and β variants. Furthermore, we found that other species of Hymenoptera possess homologs of the per α and β variants, suggesting that they have a specific function in this order of insects.