Genome wide identification ofTriboliumdorsoventral patterning genes

Abstract

The gene regulatory network controlling dorsoventral axis formation in insects has undergone drastic evolutionary changes. In Drosophila, a stable long-range gradient of Toll signalling specifies ventral cell fates and restricts BMP signalling to the dorsal half of the embryo. In Tribolium, however, Toll signalling is transient and only indirectly controls BMP signalling. In order to gain unbiased insights into the Tribolium network, we performed comparative transcriptome analyses of embryos with various dorsoventral pattering defects produced by parental RNAi for Toll and BMP signalling components. We also included embryos lacking the mesoderm ( produced by Tctwist RNAi) and characterized similarities and differences between Drosophila and Tribolium twist loss-of-function phenotypes. Using stringent conditions, we identified over 750 differentially expressed genes and analysed a subset with altered expression in more than one knockdown condition. We found new genes with localized expression and showed that conserved genes frequently possess earlier and stronger phenotypes than their Drosophila orthologues. For example, the leucine-rich repeat (LRR) protein Tartan, which has only a minor influence on nervous system development in Drosophila, is essential for early neurogenesis in Tribolium and the Tc-zinc-finger homeodomain protein 1 (Tc-zfh1), the orthologue of which plays a minor role in Drosophila muscle development, is essential for maintaining early Tc-twist expression, indicating an important function for mesoderm specification.

A large scale systemic RNAi screen in the red flour beetleTribolium castaneumidentifies novel genes involved in insect muscle development

“…Before embarking on the RNAi screen we sought evidence for similarities in muscle development between the two species of insect and tested whether RNAi-induced muscle phenotypes can be obtained for Tribolium castaneum (Tc) orthologs of myogenic regulators in Drosophila. The expression of the early mesodermal regulator Twist in the embryonic mesoderm of Tribolium has been documented extensively (Händel et al 2005;Stappert et al 2016), and as expected, RNAi against Tc-twist in pig-19 led to a complete absence of muscles (data not shown, see http://ibeetle-base.unigoettingen.de). TC002914, the single ortholog of Drosophila kirre (aka duf) and roughest (rst), which in Drosophila are essential for myoblast fusion in a functionally redundant manner, is expressed in somatic mesodermal cells of the body wall and limbs in Tribolium embryos ( Fig.…”

“…The earliest events in the hierarchy of zygotically active regulatory genes involve the activation of twist and snail in a ventral strip of cells in the blastoderm embryo, which are needed for the specification of the mesoderm and its invagination during gastrulation (Leptin 1991). Tribolium castaneum (Tc) twist, which is one of the few known regulators of mesoderm and muscle development in the red four beetle, fulfills similar early functions as Drosophila twist (Händel et al 2005;Stappert et al 2016). In Drosophila and likely in Tribolium, the subsequent spreading of the internalized mesoderm in tight contact with the overlying ectoderm is facilitated by FGF signals from the ectoderm (Wilson and Leptin 2000; Sharma et al 2015).…”

Novel functions for Dorsocross in epithelial morphogenesis in the beetle Tribolium castaneum

“…For more details on Tc-dpp RNAi see Fig. S3 and Stappert et al (2016). (G,H) After Tc-zen1 RNAi, initial Tc-Doc expression is dorsal (G, also see Fig.…”

Molecular control of gut formation in the spider Parasteatoda tepidariorum

“…This represents a deviation from the D. melanogaster paradigm, since in this dipteran twi expression is maternally activated at the ventral region under the control of Dorsal, a NF‐Kβ transcription factor (Jiang, Kosman, Ip, & Levine, ). twi is part of the gene regulatory network involved in dorsoventral patterning not only in D. melanogaster (e.g., Zeitlinger et al, ), but also in other insects (Pers et al, ; Stappert, Frey, von Levetzow, & Roth, ). Insect eggs display an extreme case of anticipation of bilateral symmetry (see introduction), thus the germ layers, including endoderm and mesoderm, are largely specified early in D. melanogaster , before gastrulation.…”