Abstract: Objective  To study the tissue localization and expression difference of endogenous β-glucosidase in digestive system of Musca domestica third instar larvae.  Methods  The digestive system of the 3rd instar larvae of Musca domestic was taken for the below tests. Tissue localization of endogenous β-glucosidase mRNA was identified by in situ hybridization. Cellulase was localized by immunohistochemistry. The enzymatic activity of β-glucosidase was measured by 3, 5-dinitrosalicylic acid（DNS） assay. The relative mRNA expression levels of M. domestica β-glucosidase gene in these organs were determined by RT-PCR.  Results  β-glucosidase mRNA， with in situ hybridization， was shown in the epithelial cells of midgut, salivary glands and foregut of the larvae. The immunohistochemical analysis on larvae tissues revealed that cellulase was produced and secreted by the epithelial cells of the midgut, salivary glands and foregut. β-glucosidase activity in salivary glands, foregut, midgut, and hindgut was（0.80±0.06）, （0.38±0.02）, （1.20±0.05） and（0.26±0.02） IU/mg, respectively. There was significant difference in β-glucosidase activity among these digestive organs （P<0.05）. The activity level of β-glucosidase was highest in midgut ［（45.45±1.27）%］, and lowest in hindgut［（9.85±0.88）%］. However, β-glucosidase gene were only expressed in the salivary gland， foregut and midgut. Significant differences in gene expression level of β-glucosidase was found among these organs（P<0.05）. The relative expression quantity of β-glucosidase gene in midgut and salivary glands were 5 and 3 times higher than that in foregut.  Conclusion  The endogenous β-glucosidase gene is expressed in the foregut, midgut and salivary glands. The midgut and salivary glands of Musca domestica 3rd instar larvae are the primary organs of this enzyme secretion.

Key words: &beta, -glucosidase；Digestive system；Musca domestica