Sec61β, a subunit of the Sec61 complex at the endoplasmic reticulum, coordinates with Ocnus in regulating Drosophila spermatogenesis.

sec61β encodes a subunit of the Sec61 translocon which is a highly conserved heterotrimer responsible for translocating the nascent polypeptides into the lumen of the endoplasmic reticulum (ER) or onto the ER membrane. In this study, we show that knockdown of sec61β in the early germline leads to male sterility in Drosophila melanogaster. These males exhibit testes that are dramatically reduced in size and devoid of germ cells. However, the somatic cells with hub markers extend abnormally beyond the stem cell niche region. Stat92E-positive cells are also expanded into the posterior region of the small testes and primarily in the nuclei. Through tracking the developmental processes of germ cells, we find that the loss of germ cells occurs during the 3rd instar larval stage. Additionally, studies in Drosophila S2 cells reveal that Sec61β can directly interact with Ocnus (Ocn), likely at the nuclear membrane. Genetically, we show that overexpression of ocn partially restores fertility in sec61β knockdown males, while overexpression of sec61β fails to compensate for the defects in male fertility induced by ocn knockdown. These findings suggest that Sec61β might play a critical role in testis development and spermatogenesis, potentially coordinating with Ocn and involving in the JAK/STAT pathway.