Characterization of a novel repetitive secretory protein specifically expressed in the modified salivary gland of Hydropsyche sp. (Trichoptera; Hydropsychidae)

Here, we report the cloning and characterization of a common salivary gland-specific gene, Nf-1, from late instar Hydropsyche sp. larvae, and show that the corresponding gene product is translated in the gland and secreted to the gland lumen. The deduced Nf-1 protein is primarily composed of five repetitive sequence units of 63-65 amino acids, and contains a putative signal sequence composed of 19 amino acids. Secreted Nf-1 (∼37 kDa) was localized to the gland lumen by Western blotting of gland and lumen fractions. Together, the structure, expression pattern and protein localization of Nf-1 indicate that this protein is likely to be a major component of the silk shields and nets produced by the aquatic insect, Trichoptera.