Drosophila SERTAD domain protein Taranis is required in somatic cells for maintenance of male germline stem cells.

BACKGROUND: Polycomb proteins are essential for maintaining stem cell identity across different stem cell niches. However, how they function to maintain stem cell niches is not fully understood. RESULTS: Here we show that the SERTAD protein Taranis (Tara), which is a Polycomb-trithorax group protein, is expressed in the adult testis niche and plays a role in its maintenance in Drosophila. We found that tara is expressed in early cyst cells, likely including somatic cyst stem cells (CySCs) of Drosophila male testis tip region, which houses both germline and somatic cyst stem cells along with the hub cells, forming the stem cell niche. Consistent with its expression, we found that, while loss of tara in germline cells only had minimal effects, tara knockdown in all cells or only in somatic cells of the niche reduced the number of not only somatic cells, but also germline stem cells (GSCs). We further found that Tara might antagonize Notch signaling in CySCs to maintain the stem cell niche. CONCLUSIONS: Our studies suggest that Tara might function in somatic CySCs for GSC maintenance in the Drosophila testis.