View Program - 63rd Annual Drosophila Research Conference

Drosophila gonads are highly sexually dimorphic with somatic and germ cell components. The karyotype (XX and XY) of somatic and germ cells must match in addition to the germ cell requiring the non-autonomous signals from soma for the production of functional gametes. Y chromosome ~40mb, is mostly heterochromatin contains ~16 known protein coding genes. The Y linked fertility factors are known to transcribe in primary spermatocytes in a specific spatiotemporal manner for ~90 hours during the spermatogenesis that is important for male fertility. Nevertheless, the Y expression if modulated by non-autonomous cues from soma has never been addressed, which is the purpose of this study.
We adapted transcriptomics and generated RNA-seq libraries from gonads of XY larvae (L3) as control and from XY larvae with ectopically expressing transformer (tra) that will allow us to investigate the Y expression when the somatic sex cue is reversed. The transcriptome analysis revealed that none of the Y linked genes that are expressed in XY gonads (12 protein coding genes, 4 pseudogenes with Transcript Per Million value >1) are expressed when the somatic sex is reversed with the exception of flagrante delicto Y (FDY) that has an autosomal paralog. Our cytological capture of Y transcription (male fertility factor kl3 (kl-3), first exon transcripts detection by insitu) supported our transcriptome analysis as kl-3 is transcribed in XY spermatocytes evidently whereas it was not in XY germ cells when the somatic sex cue is reversed. In case of XXY karyotype, kl-3 is inactive in germ cells possibly because of female cues coming from the soma. In that case it will be interesting to see if reversing the somatic sex in XXY soma leads to Y transcription that we are currently reviewing.
Our results infer that the non-autonomous male cues from soma (tra absence) are necessary for the most Y expression in XY germ cells. The male somatic cues might initiate a special transcriptional program in the germ cells that regulates Y activation which is inhibited when the somatic sex is reversed. Although, it is possible that the male cue from soma is necessary for XY germ cells to progress into the primary spermatocyte stage and proper spermatocyte specific transcription and/or parallel transcriptional program that in turn initiate Y transcription, that we are excited to investigate in near future.

Investigation of Y expression in germ cells, if it is modulated by the non-autonomous cues from soma