感染布氏白僵菌后油松毛虫血淋巴中海藻糖酶活性、海藻糖和葡萄糖含量的变化

为了揭示病原真菌白僵菌Beauveria侵染昆虫过程中如何利用虫体内糖类物质作为自身营养， 本研究测定了布氏白僵菌Beauveria brongniartii (Sacc.) Petch （2382菌株）感染油松毛虫Dendrolimus tabulaeformis Tsai et Liu幼虫后， 虫体血淋巴中酸性海藻糖降解酶活性及海藻糖和葡萄糖含量的变化。油松毛虫4龄幼虫感染菌株孢子悬浮液后， 血淋巴中酸性海藻糖降解酶的活性明显高于对照组， 感染后第3天酶活性达到最大值（0.2786 U/mg）， 此后第4-6 天酶活性逐渐降低； 染菌后的6 d中， 血淋巴中海藻糖含量显著低于对照组， 同样在感染后第4天其含量逐渐降低， 第6天时降到最低值。相比之下， 处理组血淋巴中的葡萄糖含量显著高于对照组； 处理组其含量在第1-3天内呈现快速升高趋势， 在第3天达到最大值（7.7615 mmol/L）， 然后逐渐降低。结果说明， 白僵菌侵入昆虫血淋巴后， 菌株代谢产生酸性海藻糖降解酶， 将血淋巴中的海藻糖水解成为葡萄糖， 然后为真菌利用， 破坏了虫体内的血糖平衡， 这是一个相互连接的生理代谢和生化反应过程。

Changes of trehalase activity and contents of trehalose and glucose in the hemolymph of Dendrolimus tabulaeformis (Lepidoptera: Lasiocampidae) larvae infected with Beauveria brongniartii

To reveal the approach of entomopathogenic fungus Beauveria using glucide in host insect hemolymph as nutrition, we investigated the changes of trehalase activity and contents of trehalose and glucose in larval hemolymph of Dendrolimus tabulaeformis Tsai et Liu after infection with Beauveria brongniartii (Sacc.) Petch 2382 strain. After the 4th instar larvae of D. tabulaeformis were infected with the strain, the acid trehalase activity in their hemolymph was significantly higher than that in control groups, reached the highest level (0.2786 U/mg) at 3 d after infection, and then dropped slowly during 4-6 d after infection. The trehalose content in larval hemolymph in treatment groups was significantly lower than that in the control, began to decrease at 4 d after infection and reached the lowest level at 6 d after infection, which was consistent with the dynamics of the acid trehalase activity. By contrast, the glucose content was higher in treatment groups than in the control. The glucose content in larval hemolymph in treatment groups increased quickly in 1-3 d with a peak (7.7615 mmol/L) at 3 d after infection, and then decreased gradually. These results suggest that after entering into the hemolymph of D. tabulaeformis, B. brongniartii can produce acid trehalase that hydrolyzes trehalose into glucose for the use by the fungus as nutrition, and a series of physiological metabolism and biochemical reaction result in blood sugar imbalance in host insect.