家蚕血淋巴体外黑化观察及相关黑色素合成催化酶基因

In vitro observation of haemolymph melanization and melanin-related biosynthesis enzyme genes in silkworm, Bombyx mori

摘要:

观察不同生长期家蚕幼虫血淋巴在体外的黑化速度和对大肠杆菌生长的影响结果显示，随食桑生长幼虫血淋巴的黑化速度逐渐变快，对大肠杆菌生长的抑制作用逐渐增强。RT-PCR实验显示，黑色素合成催化酶BmTan、BmPo-1、BmYellow-f和BmDdc等的基因在家蚕5 L 3 d血淋巴中表达量高，BmBlack、BmYellow和BmPah等的基因也有明显表达。qPCR分析显示，黑化病蚕中Bmtan、Bmddc、Bmyellow、Bmebony和Bmblack，尤其Bmddc表达发生了显著上调。与对照相比，Ddc酶的抑制剂能显著抑制脂多糖对血淋巴的诱导黑化作用。用大肠杆菌注射家蚕幼虫，血淋巴中多巴和多巴胺的含量明显上升。这些表明家蚕幼虫血淋巴黑化与防御免疫有关，Bmddc很可能在幼虫血淋巴的免疫黑化中发挥作用。

Abstract:

The observation statistics suggested that the haemolymph melanization speed of larvae became fast and the growth inhibition of Escherichia coli was strong as the quantities of feeding on mulberry leaves increased. The RT-PCR result showed that the mRNA expressions of melanin biosynthesis enzyme BmTan, BmPo-1, BmYellow-f and BmDdc were high in the haemolyph of 5 L 3 d larvae. The qPCR analysis showed Bmtan, Bmddc, Bmyellow, Bmebony and Bmblack, especially Bmddc expression were significantly higher in black disease larvae than in normal larvae. Compared with control, Ddc inhibitors drastically inhibited the lipopolysaccharide-induced haemolymph melanization. In addition, the content of Dopa and Dopamine markedly rose after E. coli injection. These indicated that haemolymph melanization was linked to immune defenses and Bmddc may play a role in melanization response of haemolymph immune in silkworm.