Berni Mateus, Fontenele Marcio Ribeiro, Tobias-Santos Vitoria, Caceres-Rodrigues Aline, Mury Flavia Borges, Vionette-do-Amaral Raquel, Masuda Hatisaburo, Sorgine Marcos, da Fonseca Rodrigo Nunes, Araujo Helena
Instituto de Ciências Biomédicas (ICB), Universidade Federal doRio de Janeiro, Av. Carlos Chagas Filho 373, Ilha do Fundão., Rio de Janeiro, 21941-902 RJ Brazil ; Institute of Molecular Entomology, INCT-INEM, National Institutes in Science and Technology, Macaé, Brazil ; Post-graduate Program in Morphological Sciences, Federal University of Rio de Janeiro (PCM/UFRJ), Rio de Janeiro, RJ Brazil.
Instituto de Ciências Biomédicas (ICB), Universidade Federal doRio de Janeiro, Av. Carlos Chagas Filho 373, Ilha do Fundão., Rio de Janeiro, 21941-902 RJ Brazil ; Institute of Molecular Entomology, INCT-INEM, National Institutes in Science and Technology, Macaé, Brazil.
Evodevo. 2014 Oct 27;5:38. doi: 10.1186/2041-9139-5-38. eCollection 2014.
Insect embryonic dorso-ventral patterning depends greatly on two pathways: the Toll pathway and the Bone Morphogenetic Protein pathway. While the relative contribution of each pathway has been investigated in holometabolous insects, their role has not been explored in insects with a hemimetabolous type of development. The hemimetabolous insect Rhodnius prolixus, an important vector of Chagas disease in the Americas, develops from an intermediate germ band and displays complex movements during katatrepsis that are not observed in other orders. However, little is known about the molecular events that regulate its embryogenesis. Here we investigate the expression and function of genes potentially involved in the initial patterning events that establish the embryonic dorso-ventral axis in this hemipteran.
We establish a staging system for early embryogenesis that allows us to correlate embryo morphology with gene expression profiles. Using this system, we investigate the role of Toll pathway genes during embryogenesis. Detailed analyses of gene expression throughout development, coupled with functional analyses using parental RNA interference, revealed that maternal Toll is required to establish germ layers along the dorso-ventral axis and for embryo placement along the anterior-posterior axis. Interestingly, knockdown of the Toll pathway effector Rp-dorsal appears to regulate the expression of the Bone Morphogenetic Protein antagonist Rp-short-gastrulation.
Our results indicate that Toll signals are the initiating event in dorso-ventral patterning during Rhodnius embryogenesis, and this is the first report of a conserved role for Toll in a hemipteran. Furthermore, as Rp-dorsal RNA interference generates anteriorly misplaced embryos, our results indicate a novel role for Toll signals in establishment of the anterior-posterior axis in Rhodnius.
昆虫胚胎的背腹模式形成很大程度上依赖于两条信号通路：Toll信号通路和骨形态发生蛋白信号通路。虽然在全变态昆虫中已经研究了每条信号通路的相对作用，但在半变态发育类型的昆虫中它们的作用尚未得到探索。半变态昆虫南美锥蝽是美洲恰加斯病的重要传播媒介，它从中胚带发育而来，在胚胎下沉过程中表现出其他目昆虫未观察到的复杂运动。然而，对于调节其胚胎发育的分子事件知之甚少。在这里，我们研究了可能参与建立该半翅目昆虫胚胎背腹轴的初始模式形成事件的基因的表达和功能。
我们建立了早期胚胎发育的分期系统，这使我们能够将胚胎形态与基因表达谱相关联。利用这个系统，我们研究了Toll信号通路基因在胚胎发育过程中的作用。对整个发育过程中基因表达的详细分析，结合使用亲代RNA干扰的功能分析，表明母体Toll对于沿背腹轴建立胚层以及沿前后轴放置胚胎是必需的。有趣的是，Toll信号通路效应因子Rp-dorsal的敲低似乎调节了骨形态发生蛋白拮抗剂Rp-short-gastrulation的表达。
我们的结果表明，Toll信号是南美锥蝽胚胎发育过程中背腹模式形成的起始事件，这是Toll在半翅目中保守作用的首次报道。此外，由于Rp-dorsal RNA干扰产生了前后位置错误的胚胎，我们的结果表明Toll信号在南美锥蝽前后轴建立中具有新的作用。
