Division of Plant Sciences, University of Missouri, Columbia, Missouri, USA.
USDA/Agricultural Research Service, Biological Control of Insects Research Laboratory, Columbia, Missouri, USA.
Sci Rep. 2017 Feb 22;7:43163. doi: 10.1038/srep43163.
Bursicon is a neuropeptide hormone consisting of two cystine-knot proteins (burs α and burs β), responsible for cuticle tanning and other developmental processes in insects. Recent studies show that each bursicon subunit forms homodimers that induce prophylactic immunity in Drosophila melanogaster. Here, we investigated the hypothesis that bursicon homodimers act in prophylactic immunity in insects, and possibly arthropods, generally, using the mosquito, Aedes aegypti. We found that burs α and burs β are expressed in larvae, pupae and newly emerged adults. Treating newly emerged Ae. aegypti and D. melanogaster adults with recombinant bursicon (r-bursicon) heterodimer led to cuticle tanning in both species. Treating larvae and adults with r-bursicon homodimers led to up-regulation of five anti-microbial peptide (AMP) genes, noting the possibility that bursicon heterodimers also lead to up-regulation of these genes can not been excluded. The induced AMPs effectively suppressed the growth of bacteria in vitro. RNAi knock-down of the transcriptional factor Relish2 abolished the influence of r-bursicon homodimers on AMP production. We infer the bursicon homodimers induce expression of AMP genes via Relish2 in Ae. aegypti, as prophylactic immunity to protect mosquitoes during the vulnerable stages of each molt.
骨成型蛋白是一种由两个胱氨酸结蛋白（burs α 和 burs β）组成的神经肽激素，负责昆虫的角质层鞣制和其他发育过程。最近的研究表明，每个骨成型蛋白亚基形成同源二聚体，诱导黑腹果蝇中的预防性免疫。在这里，我们使用埃及伊蚊调查了骨成型蛋白同源二聚体在昆虫，甚至可能是节肢动物中的预防性免疫中的作用的假设。我们发现burs α 和 burs β 在幼虫、蛹和新羽化的成虫中表达。用重组骨成型蛋白（r-bursicon）异源二聚体处理新羽化的埃及伊蚊和黑腹果蝇成虫会导致两种物种的角质层鞣制。用 r-bursicon 同源二聚体处理幼虫和成虫会导致五种抗菌肽（AMP）基因的上调，值得注意的是，不能排除骨成型蛋白异源二聚体也会导致这些基因的上调。诱导产生的 AMPs 有效地抑制了细菌在体外的生长。转录因子 Relish2 的 RNAi 敲低消除了 r-bursicon 同源二聚体对 AMP 产生的影响。我们推断，骨成型蛋白同源二聚体通过 Relish2 在埃及伊蚊中诱导 AMP 基因的表达，作为在每个蜕皮脆弱阶段保护蚊子的预防性免疫。
