Tudor domain-containing protein, Kotsubu, is required for proper piRNA biogenesis and transposon silencing.

Drosophila Tdrd1 orthologues, Kotsubu (Kots), is a Tudor domain-containing protein. The loss of kots resulted in a notable upregulation of stellate and a corresponding reduction in the Suppressor of Stellate piRNAs in the mutants. Furthermore, a moderate yet significant reduction of other piRNAs was observed in kots mutant testes, albeit to a weaker extent in mutant ovaries.