Female-germline specific protein Sakura interacts with Otu and is crucial for germline stem cell renewal and differentiation and oogenesis.

During oogenesis, self-renewal and differentiation of germline stem cells (GSCs) must be tightly regulated. The female germline serves as an excellent model for studying these regulatory mechanisms. Here, we report that a previously uncharacterized gene , which we named , is essential for oogenesis and female fertility in . Sakura is predominantly expressed in the ovaries, particularly in the germline cells, including GSCs. null mutant female flies display rudimentary ovaries with germline-less and tumorous phenotypes, fail to produce eggs, and are completely sterile. The germline-specific depletion of impairs Dpp/BMP signaling, leading to aberrant ( ) expression, resulting in faulty differentiation and loss of GSCs. is also necessary for normal levels of piwi-interacting RNAs (piRNAs) levels and for female-specific splicing of ( ), a master regulator of sex identity determination. We identified Ovarian Tumor (Otu) as a protein binding partner of Sakura and found that loss of phenocopies loss of in ovaries. Thus, we identify Sakura as a crucial factor for GSC renewal and differentiation and oogenesis, and propose that Sakura and Otu function together in these processes.