Transcriptomic analysis of the honey bee (Apis mellifera) queen spermathecae reveals genes that may be involved in sperm storage after mating.

Honey bee (Apis mellifera) queens have a remarkable organ, the spermatheca, which successfully stores sperm for years after a virgin queen mates. This study uniquely characterized and quantified the transcriptomes of the spermathecae from mated and virgin honey bee queens via RNA sequencing to identify differences in mRNA levels based on a queen's mating status. The transcriptome of drone semen was analyzed for comparison. Samples from three individual bees were independently analyzed for mated queen spermathecae and virgin queen spermathecae, and three pools of semen from ten drones each were collected from three separate colonies. In total, the expression of 11,233 genes was identified in mated queen spermathecae, 10,521 in virgin queen spermathecae, and 10,407 in drone semen. Using a cutoff log2 fold-change value of 2.0, we identified 212 differentially expressed genes between mated and virgin spermathecal queen tissues: 129 (1.4% of total) were up-regulated and 83 (0.9% of total) were down-regulated in mated queen spermathecae. Three genes in mated queen spermathecae, three genes in virgin queen spermathecae and four genes in drone semen that were more highly expressed in those tissues from the RNA sequencing data were further validated by real time quantitative PCR. Among others, expression of Kielin/chordin-like and Trehalase mRNAs was highest in the spermathecae of mated queens compared to virgin queen spermathecae and drone semen. Expression of the mRNA encoding Alpha glucosidase 2 was higher in the spermathecae of virgin queens. Finally, expression of Facilitated trehalose transporter 1 mRNA was greatest in drone semen. This is the first characterization of gene expression in the spermathecae of honey bee queens revealing the alterations in mRNA levels within them after mating. Future studies will extend to other reproductive tissues with the purpose of relating levels of specific mRNAs to the functional competence of honey bee queens and the colonies they head.

A shared enhancer controls a temporal switch between promoters during Drosophila primary sex determination.

Sex-lethal (Sxl), the master regulatory gene of Drosophila somatic sex determination, is stably maintained in an on or an off state by autoregulatory control of Sxl premRNA processing. Establishment of the correct Sxl splicing pattern requires the coordinate regulation of two Sxl promoters. The first of these promoters, SxlPe, responds to the female dose of two X chromosomes to produce a pulse of Sxl protein that acts on the premRNA products from the second promoter, SxlPm, to establish the splicing loop. SxlPm is active in both sexes throughout most of development, but nothing is known about how SxlPm is expressed during the transition from X signal assessment to maintenance splicing. We found that SxlPm is activated earlier in females than in males in a range of Drosophila species, and that its expression overlaps briefly with that of SxlPe during the syncytial blastoderm stage. Activation of SxlPm depends on the scute, daughterless, and runt transcription factors, which communicate X chromosome dose to SxlPe, but is independent of the X signal element sisA and the maternal co-repressor groucho. We show that DNA sequences regulating the response of SxlPe to the X chromosome dose also control the sex-differential response of SxlPm. We propose that co-expression of Sxl protein and its premRNA substrate facilitates the transition from transcriptional to splicing control, and that delayed activation of SxlPm in males buffers against the inappropriate activation of Sxl by fluctuations in the strength of the X chromosome signal.