Study of the role of ecdysteroid for insect diapause

许多研究表明，幼虫和蛹的滞育是由蜕皮激素缺乏维持的，然而，触发滞育的内分泌线索仍然不是很清楚。因此，我们研究了蜕皮激素在诱导基点斑点叉尾轮虫幼虫滞育中的作用。当向非滞育的巴西斑潜蝇幼虫注射从Rileyi Nomuraea rileyi中鉴定的蜕皮类固醇失活酶E22O时，它们在不吃任何东西的情况下存活了几个月。注入E22O的幼虫也获得了高抗寒性，这是滞育昆虫经常观察到的特征。此外，它们在暴露在寒冷条件下后恢复发育，这是许多昆虫打破滞育的环境刺激。这些发育和存活特征与正常滞育幼虫没有明显区别，这有力地表明E220注射诱导了巴西斑潜蝇幼虫的滞育。据我们所知，这是第一个表明蜕皮类固醇滴度降低是足够的内分泌刺激来诱导昆虫滞育的报告。

Many researches suggested that larval and pupal diapauses are maintained by ecdysteroid deficiency, however, the endocrinological cue to trigger diapause is still not very clear. We therefore examined the role of ecdysteroid for the induction of the larval diapause of Haritalodes basipunctalis. When non-diapausing larvae of H. basipunctalis were injected with an ecdysteroid inactivating enzyme ecdysteroid-22-oxidase(E22O) identified from Nomuraea rileyi, they survived for a few months without eating anything. The E22O-injected larvae also acquired high cold-hardiness, a characteristic often observed in insects in diapause. Furthermore, they resumed development after being exposed to chilling conditions, which is the environmental stimulus to break diapause in many insect species. These developmental and survival characteristics were indistinguishable from those of the normal diapausing larvae, suggesting strongly that the E220 injection induced the larval diapause in H. basipunctalis. To the best of our knowledge, this is the first report indicating that a reduction in the ecdysteroid titer is a sufficient endocrinological stimulus to induce diapauses in insects.