关键词: 家蚕, Toll样受体, BmToll9-2, 脂多糖, 大肠杆菌, 基因表达

Abstract: 【Aim】 Toll-like receptors are important members in Toll signaling pathway in insects and play an important role in activating the innate immune response to invading pathogenic microorganisms. This study aims to explore the influence of lipopolysaccharide (LPS) on the expression of the Toll-like receptor gene BmToll9-2 in larvae of the silkworm， Bombyx mori. 【Methods】 The expression profiles of BmToll9-2 in epidermis， fat body， Malpighian tubules， midgut， brain， silk glands and thoracic muscles of the 4th and 5th instar larvae of B. mori strain Dazao were detected by RT-PCR. LPS and Escherichia coli were respectively injected into the body cavity of the 5th instar larvae to induce their immune response， and the expression levels of BmToll9-2 in the midgut at different time after injection were detected by real-time quantitative PCR. 【Results】 RT-PCR results revealed that BmToll9-2 was highly expressed not only in the fat body， Malpighian tubules， brain and silk glands of the 4th instar larvae of B. mori， but also in the fat body， midgut， Malpighian tubules and brain of the 5th instar larvae. The real-time quantitative PCR results showed that injection of LPS could induce the transcription of BmToll9-2 in the midgut of the 5th instar larvae， and the best induction effect was at 6 h after injection. Injection of E. coli could also induce the transcription of BmToll9-2 in the midgut of the 5th instar larvae， and the best induction effect was at 3 and 6 h after injection. 【Conclusion】 Expression of BmToll9-2 in B. mori larvae is up-regulated after  injection of LPS and E. coli，suggesting that BmToll9-2 receptor may be involved in the recognition process of Toll-like receptors to LPS and E. coli in insects.

Key words: Bombyx mori, Toll-like receptor, BmToll9-2, lipopolysaccharide, Escherichia coli, gene expression