Department of Zoology, North-Eastern Hill University, Shillong, Meghalaya, India.
Insect Sci. 2021 Jun;28(3):680-691. doi: 10.1111/1744-7917.12802. Epub 2020 Jul 22.
In Bombyx mori, two dorsolateral neurosecretory cells (NSCs) in each of the two brain lobes have been identified as prothoracicotropic hormone (PTTH) producing cells. This neuropeptide in insects stimulates the prothoracic gland for the synthesis and release of ecdysone, responsible for the molting events. Allatotropin (AT) and allatostatin (AST) are allatoregulatory neuropeptides that regulate juvenile hormone biosynthesis. Here, by using RT-qPCR, we showed that in B. mori, nutritional stress modulates the mRNA expression of AT and AST-C (allatostain type C) in the central nervous system consisting of the brain lobes and all the associated ganglia. Using whole-mount in situ hybridization, we showed that the feeding status of Bombyx larvae also influences the expression of PTTH in the NSCs of the brain. Food deprivation significantly decreased the mRNA expression levels of PTTH in larvae at active or terminal growth period. Further, we showed that insulin modulates the expression level of PTTH. However, its action was dependent on the feeding status of the larvae. At feeding, the insulin decreased the PTTH expression level, while at food deprivation, the insulin increased the PTTH expression level. The data thus indicates that larval feeding status plays an important role in altering the mRNA expression levels of allatoregulatory peptide genes and PTTH.
在家蚕中，每个脑叶的两个背外侧神经分泌细胞（NSC）已被鉴定为促前胸腺激素（PTTH）产生细胞。这种昆虫神经肽刺激前胸腺合成和释放蜕皮激素，负责蜕皮事件。促前胸腺激素（AT）和前胸腺抑制素（AST）是调节保幼激素生物合成的神经肽。在这里，我们通过 RT-qPCR 显示，在营养胁迫下，家蚕中枢神经系统（由脑叶和所有相关神经节组成）中 AT 和 AST-C（前胸腺抑制素 C）的 mRNA 表达受到调节。通过全胚胎原位杂交，我们表明家蚕幼虫的摄食状态也影响脑中 NSCs 中 PTTH 的表达。在活跃或终末生长期，禁食显著降低了幼虫中 PTTH 的 mRNA 表达水平。此外，我们表明胰岛素调节 PTTH 的表达水平。然而，其作用取决于幼虫的摄食状态。在摄食时，胰岛素降低了 PTTH 的表达水平，而在禁食时，胰岛素增加了 PTTH 的表达水平。因此，数据表明幼虫的摄食状态在改变神经肽和 PTTH 的基因表达水平方面起着重要作用。
