Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
Institute of Plant Protection, Xinjiang Academy of Agricultural Sciences, Urumqi, China.
Insect Mol Biol. 2021 Jun;30(3):241-252. doi: 10.1111/imb.12691. Epub 2021 Jan 7.
In Drosophila melanogaster, ecdysis triggering hormone (ETH) is the key factor triggering ecdysis behaviour and promoting trachea clearance. However, whether ETH plays the dual roles in non-dipteran insects is unknown. In this survey, we found that Ldeth mRNA levels were positively correlated with circulating 20-hydroxyecdysone (20E) titers in Leptinotarsa decemlineata. Ingestion of an ecdysteroid agonist halofenozide or 20E stimulated the transcription of Ldeth, whereas RNA interference (RNAi) of ecdysteroidogenesis (LdPTTH or LdSHD) or 20E signalling (LdEcR, LdUSP or LdFTZ-F1) genes inhibited the expression, indicating ETH acts downstream of 20E. RNAi of Ldeth at the final instar stage impaired pupation. More than 80% of the Ldeth-depleted beetles remained as prepupae, completely wrapped in the old larval cuticles. These prepupae became withered, dried and darkened gradually, and finally died in soil. The remaining Ldeth hypomorphs pupated and emerged as abnormal adults, bearing smaller and wrinkle elytrum and hindwing. Moreover, the tracheae in the Ldeth hypomorphs were full of liquid. We accordingly proposed that the failure of trachea clearance disenabled air-swallowing after pupa-adult ecdysis and impacted wing expansion. Our results suggest that ETH plays the dual roles, initiation of ecdysis and motivation of trachea clearance, in a coleopteran.
在黑腹果蝇中，蜕皮激素释放激素（ETH）是触发蜕皮行为和促进气管清除的关键因素。然而，ETH 是否在非双翅目昆虫中发挥双重作用尚不清楚。在这项研究中，我们发现 Ldeth mRNA 水平与美洲大蠊体内循环的 20-羟基蜕皮酮（20E）浓度呈正相关。蜕皮甾类激素激动剂 halofenozide 或 20E 的摄入刺激了 Ldeth 的转录，而蜕皮甾类生物合成（LdPTTH 或 LdSHD）或 20E 信号（LdEcR、LdUSP 或 LdFTZ-F1）基因的 RNA 干扰（RNAi）抑制了其表达，表明 ETH 作用于 20E 下游。在最后一个龄期阶段对 Ldeth 进行 RNAi 干扰会损害化蛹。超过 80%的 Ldeth 敲低的甲虫仍处于预蛹期，完全被旧的幼虫外骨骼包裹。这些预蛹逐渐变得枯萎、干燥和变暗，最终在土壤中死亡。剩余的 Ldeth 功能不全型个体化蛹并异常羽化成为成虫，其鞘翅和后翅更小且有褶皱。此外，Ldeth 功能不全型个体的气管充满了液体。因此，我们提出气管清除的失败使蛹-成虫蜕皮后无法进行空气吞咽，从而影响了翅膀的展开。我们的研究结果表明，ETH 在鞘翅目昆虫中发挥双重作用，即启动蜕皮和促进气管清除。
