追寄蝇寄生对家蚕龄期经过的影响及其机制

Effects of Exorista Sorbillans Parasitization on the Instar Duration of the Host Silkworm Bombyx mori and the Underlying Mechanism

家蚕追寄蝇(Exorista sorbillans Wiedemann)是危害蚕业生产的重要害虫。为深入了解家蚕追寄蝇对家蚕龄期经过的影响及其机制,本研究将5龄第1 d的家蚕用于追寄蝇寄生,记录家蚕从5龄起蚕至预蛹期第1 d的时间,并解剖和收集寄生后1 d、3 d和5 d的家蚕血清、前胸腺和脂肪体,分别检测20E(20-hydroxyecdysone)滴度、20E合成酶基因转录水平和20E下游基因转录水平。结果表明:追寄蝇寄生的家蚕从5龄起蚕至预蛹期历经10.1 d,发育时间比对照组缩短了0.7 d。同时,在追寄蝇寄生3 d和5 d后,家蚕的20E滴度与对照组相比均显著上升,且20E合成酶基因和下游响应基因的转录水平均发生改变。20E滴度的上升和下游响应基因转录水平的改变可能是引起家蚕龄期经过缩短的重要原因。

Exorista sorbillans is an important pest to harm sericulture production.In order to understand the effect and underlying mechanism of the Exorista sorbillans parasitization on the silkworm instar duration,this study employed day 1 of 5th instar silkworm to be parasitized by E.sorbillans,recorded the time from the first day of 5th instar to the first day of prepupal stage of Bombyx mori,and dissected and collected the serum,anterior thymus and fat body of B.mori for detecting the titer of 20-hydroxyecdysone,the transcriptional levels of 20E synthetase genes and 20E downstream genes.The results showed that parasitized B.mori took average 10.1 days from the 5th instar to the prepupal stage,the development time was 0.7 days shorter than the control group.Meanwhile,at the 3th and 5th day after parasitization,the 20E titer of parasitized B.mori was significantly increased,and the transcriptional levels of 20E synthetase genes and 20E downstream response genes changed.The rise of 20E titer and the change of the transcriptional levels of 20E downstream response genes may be a significant reason for the shortening of silkworm instar duration.