Identification of BmELP as an interaction partner of Bmtutl-519 in the silkworm, Bombyx mori

Abstract

Abstract The Turtle protein could act as a signaling receptor or function as a membrane-bound ligand for an unknown receptor. Alternatively, the Turtle protein could function as a co-receptor in a multi-protein receptor complex. Earlier work on the function of Bmtutl-519 suggested that it may act as a cell surface receptor or as a regulatory factor in the infection process of Nosema bombycis. To further investigate the function of Bmtutl-519 in the process of microsporidian infection and the possible regulatory pathways involved, we performed yeast two-hybrid screening on a silkworm midgut cDNA library and identified a Bombyx mori extensin-like protein/BmELP as a binding partner of Bmtutl-519. The interaction between Bmtutl-519 and BmELP was verified by GST pull-down and co-immunoprecipitation assays. Quantitative RT-PCR analysis showed that BmELP was commonly expressed in all of the examined tissues of the silkworm, and the expression was highest in the head. Moreover, BmELP was expressed throughout the entire development period, and the lowest levels of expression were observed at the egg stage. The results of infection experiments showed that N. bombycis infection caused the up-regulation of BmELP expression, especially in vitro. Taken together, our findings may provide new insights into the roles of BmELP and Bmtutl-519 in microsporidian infection.