家蚕幼虫BmToll9基因对肽聚糖和金黄色葡萄球菌的响应表达

【目的】Toll信号通路是昆虫中重要的免疫信号通路,其中Toll受体在保持Toll通路的正常免疫应答、抵抗外源病原体中起到关键的作用。本研究旨在探究肽聚糖和金黄色葡萄球菌Staphylococcus aureus对家蚕Bombyx mori Toll受体基因BmToll9-1和BmToll9-2表达的影响。【方法】将革兰氏阳性菌细胞壁主要成分肽聚糖和革兰氏阳性菌金黄色葡萄球菌分别注射感染家蚕5龄第1天幼虫,诱导其发生免疫反应;采用实时荧光定量PCR分析注射后不同感染时间点BmToll9-2和BmToll9-1基因在家蚕幼虫中肠、表皮、脂肪体和丝腺中的相对表达水平。【结果】往家蚕5龄幼虫中注射肽聚糖或金黄色葡萄球菌后,BmToll9-2基因出现了时间和组织的差异性表达。注射肽聚糖和金黄色葡萄球菌均能诱导5龄幼虫中肠BmToll9-2基因的表达上调,注射肽聚糖和金黄色葡萄球菌分别在3和6 h时对基因表达的诱导效果最好,且注射金黄色葡萄球菌比注射肽聚糖对基因表达的诱导效果更好。注射金黄色葡萄球菌能引起5龄幼虫表皮、脂肪体和丝腺中BmToll9-2基因的表达上调,分别于注射后24, 6和24 h时诱导效果最好。注射金黄色葡萄球菌亦能诱导同源的BmToll9-1基因的上调表达。【结论】家蚕幼虫BmToll9基因在肽聚糖或金黄色葡萄球菌注射处理后均能在不同组织中发生上调表达,推测BmToll9基因参与了家蚕对肽聚糖和金黄色葡萄球菌的免疫反应。

Expression of BmToll9 genes responding to peptidoglycan and Staphylococcus aureus in larval Bombyx mori

【Aim】 Toll receptors of Toll signaling pathway, an important immune signaling pathway of insects, are essential to maintain immune response against invading exogenous microorganisms in insects. This study aims to explore the influence of peptidoglycan (PGN) and Staphylococcus aureus on the expression of the Toll receptor genes BmToll9-1 and BmToll9-2 in the silkworm, Bombyx mori. 【Methods】 PGN, the main component in cell wall of Gram-positive bacteria, and a Gram-positive bacterium S. aureus were respectively injected into the day-1 5th instar larvae of B. mori to induce the immune response. The relative expression levels of BmToll9-2 and BmToll9-1 in the midgut, epidermis, fat body and silk glands of the larvae at different time points post injection were detected by real-time quantitative PCR. 【Results】 After injection of PGN or S. aureus into the 5th instar larvae of B. mori, BmToll9-2 was differentially expressed at different time points and in different tissues. Injection of PGN or S. aureus induced up-regulation of the expression of BmToll9-2 in the midgut of the 5th instar larvae, achieving the best induction effect at 3 and 6 h post injection, respectively, and the induction effect of S. aureus was better than that of PGN. Injection of S. aureus induced up-regulation of the expression of BmToll9-2 in the epidermis, fat body and silk glands of the 5th instar larvae, achieving the best induction effects at 24, 6, and 24 h post injection, respectively. Injection of S. aureus also induced up-regulation of the expression of the homogenous BmToll9-1. 【Conclusion】 The expression of BmToll9 genes in different tissues of B. mori larvae is up-regulated after injection of PGN or S. aureus, suggesting that BmToll9 genes are involved in the immune response of B. mori against PGN and S. aureus.