5龄家蚕中肠β-呋喃果糖苷酶基因转录表达分析

Transcriptional expression of β-fructofuranosidase gene in midgut of the 5^(th) instar Bombyx mori larvae

【目的】探明5龄家蚕中肠β-呋喃果糖苷酶基因表达及其酶活性变化规律,为解析家蚕回避桑叶1-脱氧野尻霉素(DNJ)毒害作用的适应机制提供参考依据。【方法】通过实时荧光定量PCR对5龄家蚕中肠β-呋喃果糖苷酶基因Bm Suc1和Bm Suc2的表达进行定量检测和分析,同时测定β-呋喃果糖苷酶活性。【结果】Bm Suc1基因在5龄家蚕中肠的不同发育阶段均有表达,其中在5龄起蚕和盛食期的相对表达量较高;而Bm Suc2基因在整个5龄期的相对表达量均非常低。从5龄起蚕到熟蚕,β-呋喃果糖苷酶活性呈先升高后降低的变化趋势,以第5 d(盛食期)的酶活性最高,达158.82U/mg。【结论】Bm Suc1基因表达水平及β-呋喃果糖苷酶活性变化规律与5龄家蚕吸收利用桑叶蔗糖营养的生理进程基本一致,提示Bm Suc1基因作为一种蔗糖水解酶基因在家蚕中肠组织消化吸收桑叶蔗糖营养物质的过程中发挥主导作用。

【Objective】In order to provide reference for illustrating adaptive mechanism of Bombyx mori avoiding toxicity of 1-deoxynojirimycin（DNJ）, the present study was conducted to investigate change regularities of β-fructofuranosidase gene expression and its enzyme activity in the midgut of the 5^（th）instar B. mori larvae. 【Method】The real-time fluorescent quantitative PCR was applied to analyze expression of Bm Suc1 and Bm Suc2 genes in midgut of the 5^（th）instar B.mori larvae, meanwhile the activities of β-fructofuranosidase were determined. 【Result 】Bm Suc1 gene was expressed in midgut of the 5^（th）instar larvae at different developmental stages, moreover it was highly expressed at moulting and glutonous stages of the 5^（th）instar larvae, while Bm Suc2 gene was lowly expressed all the time at the 5^（th）instar of larvae. Furthermore, the activity of β-fructofuranosidase showed a trend of ascending first and then descending from newly moulted silkworm to matured silkworm, especially at the 5^（th）day of glutonous stage with the highest enzyme activity（158.82 U/mg）.【Conclusion】The expression level of Bm Suc1 gene and Chang of β-fructofuranosidase activity are corresponded with mulberry sucrose metabolism in the 5^（th）instar larvae, therefore, it is revealed that Bm Suc1 gene plays a leading role in midgut absorbing sucrose nutrition from mulberry leaves.