The Yip1–Yif1 Complex Mediates the Translocation of Polar Tube Protein and Spore Wall Protein in the Microsporidian Nosema bombycis

Abstract Microsporidia are obligate intracellular parasites that proliferate within host cells. The endoplasmic reticulum (ER) system is essential for protein secretion, yet its trafficking mechanisms in microsporidia remain largely unexplored. In eukaryotes, the Yip1–Yif1 complex is a key regulator of ER-to-Golgi transport, but its function in microsporidia has not been characterized. This study demonstrates its involvement in protein transport in Nosema bombycis. Immunoprecipitation and yeast two-hybrid analyses revealed that the NbYip1 and NbYif1 interacted with NbSec61α, NbRab1b, NbPTP2, NbPTP3, NbSWP12, and NbSWP30. Furthermore, knocking down NbYip1 and NbYif1 resulted in significant downregulation and abnormal localization of two representative spore wall proteins (NbSWP12 and NbSWP30). Importantly, knockdown of both genes significantly inhibited parasite proliferation, as evidenced by reduced Nbβ-tubulin copy numbers. Overall, our findings provide the first insight into Yip1–Yif1 function in microsporidian protein translocation and suggest this complex as a potential target for controlling N. bombycis infection.