不同寄主对小线角木蠹蛾幼虫消化解毒酶的影响

小线角木蠹蛾Streltzoviella insularis是一种重要的林木蛀干害虫,在我国北方地区广泛分布,其寄主范围广,尤其对城市园林树种威胁严重。本研究测定了小线角木蠹蛾幼虫分别取食3种喜食寄主(洋白蜡、银杏和国槐)和4种普通寄主(旱柳、栾树、香椿、毛桃)后的解毒酶(细胞色素P450酶、谷胱甘肽S转移酶和羧酸酯酶)和消化酶(内切-β-1,4-葡聚糖酶、外切-β-1,4-纤维二糖水解酶、β-葡萄糖苷酶和木聚糖酶)的活性。结果表明,不同寄主对小线角木蠹蛾幼虫的消化酶和解毒酶都存在显著影响,其中取食普通寄主的幼虫3种解毒酶的平均活性(P450、GST和CarE酶活性分别为21.12、4876.86、0.035μmoL/min/mg protein)均高于取食喜食寄主的幼虫(P450、GST和CarE酶活性分别为15.87、3760.55、0.027μmoL/min/mg protein),且普通寄主的平均次生代谢物质含量更高(普通寄主总酚、类黄酮和单宁含量分别为173.10、110.07、88.77 mg/g,喜食寄主为105.22、14.05、55.74 mg/g);而取食普通寄主与喜食寄主的幼虫EG和CBH酶活性之间没有显著差异,仅取食普通寄主的幼虫β-葡糖苷酶活性和木聚糖酶活性略高于取食喜食寄主的幼虫,幼虫的消化酶活性(纤维素酶和半纤维素酶)和寄主营养物质(纤维素和半纤维素)并未在普通寄主和喜食寄主中表现出明显趋势。因此本研究认为小线角木蠹蛾的寄主适应性与寄主次生代谢物质(总酚、类黄酮和单宁)含量的关联性更强,而与营养物质(纤维素和半纤维素)含量的相关性较弱。

Detoxification and digestive enzyme activities in Streltzoviella insularis(Staudinger)larvae(Lepidoptera:Cossidae)in response to host trees

Streltzoviella insularis is a trunk borer pest that attacks many host trees,widely distributed in the northern area of China.Its host range is wide,and it especially poses a serious threat to urban garden tree species.In this study,we measured the activities of detoxification enzymes(cytochrome P450s,glutathione S-transferases,and carboxylesterases)and digestive enzymes(endo-β-1,4-glucanases,exo-β-1,4-cellobiohydrolases,β-glucosidases,and xylanases)in larvae fed on three preferred host trees(Fraxinus pennsylvanica,Ginkgo biloba,and Sophora japonica)and four occasional hosts(Salix matsudana,Koelreuteria paniculata,Toona sinensis,and Amygdalus persica).The results indicated that different hosts affected the detoxification and digestive enzyme activities in larvae.Detoxification enzyme activities were higher in larvae feeding on occasional hosts(the activities of P450,GST and CarE were 21.12,4876.86,0.035μmoL/min/mg protein,respectively)than the preferred host trees(the activities of P450,GST and CarE were 15.87,3760.55 and 0.027μmoL/min/mg protein,respectively).Occasional hosts also had higher contents of secondary metabolites(the contents of total phenol,flavonoid,and tannin in occasional hosts were 173.10,110.07 and 88.77 mg/g,while in preferred hosts were 105.22,14.05 and 55.74 mg/g,respectively).However,there were no significant differences in the activities of endo-β-1,4-glucanases and exo-β-1,4-cellobiohydrolases between larvae fed on occasional hosts and preferred hosts.The activities ofβ-glucosidases and xylanases in larvae fed on occasional hosts were slightly higher than those fed on preferred hosts.The digestive enzyme activity(cellulase and hemicellulase)and host nutrients(cellulose and hemicellulose)of larvae did not show a significant trend between occasional hosts and preferred hosts.These combined results suggest that secondary metabolites are more closely related to S.insularis host selection,whereas the correlation between nutrients(cellulose and hemicellulose)and host adaptability is relatively weak.