The iBeetle large-scale RNAi screen reveals gene functions for insect development and physiology.

Schmitt-Engel C, Schultheis D, Schwirz J, Ströhlein N, Troelenberg N, Majumdar U, Dao VA, Grossmann D, Richter T, Tech M, Dönitz J, Gerischer L, Theis M, Schild I, Trauner J, Koniszewski ND, Küster E, Kittelmann S, Hu Y, Lehmann S, Siemanowski J, Ulrich J, Panfilio KA, Schröder R, Morgenstern B, Stanke M, Buchhholz F, Frasch M, Roth S, Wimmer EA, Schoppmeier M, Klingler M, Bucher G.

Nat Commun. 2015 Jul 28;6:7822. doi: 10.1038/ncomms8822



Genetic screens are powerful tools to identify the genes required for a given biological process. However, for technical reasons, comprehensive screens have been restricted to very few model organisms. Therefore, although deep sequencing is revealing the genes of ever more insect species, the functional studies predominantly focus on candidate genes previously identified in Drosophila, which is biasing research towards conserved gene functions. RNAi screens in other organisms promise to reduce this bias. Here we present the results of the iBeetle screen, a large-scale, unbiased RNAi screen in the red flour beetle, Tribolium castaneum, which identifies gene functions in embryonic and postembryonic development, physiology and cell biology. The utility of Tribolium as a screening platform is demonstrated by the identification of genes involved in insect epithelial adhesion. This work transcends the restrictions of the candidate gene approach and opens fields of research not accessible in Drosophila.





The single fgf receptor gene in the beetle Tribolium castaneum codes for two isoforms that integrate FGF8- and Branchless-dependent signals.


Sharma R, Beer K, Iwanov K, Schmöhl F, Beckmann PI, Schröder R.

Developmental Biology 2015 Jun 15;402(2):264-75. doi: 10.1016/j.ydbio.2015.04.001.


The precise regulation of cell-cell communication by numerous signal-transduction pathways is fundamental for many different processes during embryonic development. One important signalling pathway is the evolutionary conserved fibroblast-growth-factor (FGF)-pathway that controls processes like cell migration, axis specification and mesoderm formation in vertebrate and invertebrate animals. In the model insect Drosophila, the FGF ligand / receptor combinations of FGF8 (Pyramus and Thisbe) / Heartless (Htl) and Branchless (Bnl) / Breathless (Btl) are required for the migration of mesodermal cells and for the formation of the tracheal network respectively with both the receptors functioning independently of each other. However, only a single fgf-receptor gene (Tc-fgfr) has been identified in the genome of the beetle Tribolium. We therefore asked whether both the ligands Fgf8 and Bnl could transduce their signal through a common FGF-receptor in Tribolium. Indeed, we found that the function of the single Tc-fgfr gene is essential for mesoderm differentiation as well as for the formation of the tracheal network during early development. Ligand specific RNAi for Tc-fgf8 and Tc-bnl resulted in two distinct non-overlapping phenotypes of impaired mesoderm differentiation and abnormal formation of the tracheal network in Tc-fgf8- and Tc-bnl(RNAi) embryos respectively. We further show that the single Tc-fgfr gene encodes at least two different receptor isoforms that are generated through alternative splicing. We in addition demonstrate through exon-specific RNAi their distinct tissue-specific functions. Finally, we discuss the structure of the fgf-receptor gene from an evolutionary perspective.


The first myriapod genome sequence reveals conservative arthropod gene content and genome organisation in the centipede Strigamia maritima.

Chipman AD, Ferrier DE, Brena C, Qu J, Hughes DS, Schröder R, Torres-Oliva M, Znassi N, Jiang H, Almeida FC, Alonso CR, Apostolou Z, Aqrawi P, Arthur W, Barna JC, Blankenburg KP, Brites D, Capella-Gutiérrez S, Coyle M, Dearden PK, Du Pasquier L, Duncan EJ, Ebert D, Eibner C, Erikson G, Evans PD, Extavour CG, Francisco L, Gabaldón T, Gillis WJ, Goodwin-Horn EA, Green JE, Griffiths-Jones S, Grimmelikhuijzen CJ, Gubbala S, Guigó R, Han Y, Hauser F, Havlak P, Hayden L, Helbing S, Holder M, Hui JH, Hunn JP, Hunnekuhl VS, Jackson L, Javaid M, Jhangiani SN, Jiggins FM, Jones TE, Kaiser TS, Kalra D, Kenny NJ, Korchina V, Kovar CL, Kraus FB, Lapraz F, Lee SL, Lv J, Mandapat C, Manning G, Mariotti M, Mata R, Mathew T, Neumann T, Newsham I, Ngo DN, Ninova M, Okwuonu G, Ongeri F, Palmer WJ, Patil S, Patraquim P, Pham C, Pu LL, Putman NH, Rabouille C, Ramos OM, Rhodes AC, Robertson HE, Robertson HM, Ronshaugen M, Rozas J, Saada N, Sánchez-Gracia A, Scherer SE, Schurko AM, Siggens KW, Simmons D, Stief A, Stolle E, Telford MJ, Tessmar-Raible K, Thornton R, van der Zee M, von Haeseler A, Williams JM, Willis JH, Wu Y, Zou X, Lawson D, Muzny DM, Worley KC, Gibbs RA, Akam M, Richards S.


PLoS Biol. 2014 Nov 25;12(11):e1002005. doi: 10.1371/journal.pbio.1002005



Myriapods (e.g., centipedes and millipedes) display a simple homonomous body plan relative to other arthropods. All members of the class are terrestrial, but they attained terrestriality independently of insects. Myriapoda is the only arthropod class not represented by a sequencedgenome. We present an analysis of the genome of the centipede Strigamia maritima. It retains a compact genome that has undergone less gene loss and shuffling than previously sequenced arthropods, and many orthologues of genes conserved from the bilaterian ancestor that have been lost in insects. Our analysis locates many genes in conserved macro-synteny contexts, and many small-scale examples of gene clustering. We describe several examples where S. maritima shows different solutions from insects to similar problems. The insect olfactory receptor gene family is absent from S. maritima, and olfaction in air is likely effected by expansion of other receptor gene families. For some genes S. maritima has evolved paralogues to generate coding sequence diversity, where insects use alternate splicing. This is most striking for the Dscam gene, which in Drosophila generates more than 100,000 alternate splice forms, but in S. maritima is encoded by over 100 paralogues. We see an intriguing linkage between the absence of any known photosensory proteins in a blind organism and the additional absence of canonical circadian clock genes. The phylogenetic position of myriapods allows us to identify where in arthropod phylogeny several particular molecular mechanisms and traits emerged. For example, we conclude that juvenile hormone signalling evolved with the emergence of the exoskeleton in the arthropods and that RR-1 containing cuticle proteins evolved in the lineage leading to Mandibulata. We also identify when various gene expansions and losses occurred. The genome of S. maritima offers us a unique glimpse into the ancestral arthropod genome, while also displaying many adaptations to its specific life history.


FGF signalling controls anterior extraembryonic and embryonic fate in the beetle Tribolium

Rahul Sharma, Anke Beermann & Reinhard Schröder

Developmental Biology, 381(1):121-133

DOI: 10.1016/j.ydbio.2013.05.031  Epub 2013 Jun 12



Fibroblast growth factor (FGF) signalling plays a key role in early embryonic development and cell migration in vertebrates and in invertebrates. To gain novel insights into FGF signalling in an arthropod, we characterized the fgf1b ortholog in the beetle Tribolium that is not represented in the Drosophila genome.

We found that FGF1b dependent signalling organizes the anterior to posterior axis of the early embryo. The loss of Tc-fgf1b function in Tribolium by RNA interference resulted in the reduction of the anteriormost extraembryonic fate, in an anterior shift of embryonic fate and in the loss or malformation of anterior embryonic structures. Without intact extraembryonic membranes the serosa and the amnion, Tc-fgf1bRNAi embryos did not undergo morphogenetic movements and remained posteriorly localized throughout embryogenesis. Only weakly affected embryos developed into a cuticle that show dorsally curved bodies with head defects and a dorsal opening. Except for the posterior dorsal amnion, the overall topology of the dorsal–ventral axis seemed unaffected. Moreover, FGF signalling was not required for the onset of mesoderm formation but for fine-tuning this tissue during later development. We also show that in affected embryos the dorsal epidermis was expanded and expressed Tc-dpp at a higher level.

We conclude that in the Tribolium blastoderm embryo, FGF1-signalling organizes patterning along the AP-axis and also balances the expression level of Dpp in the dorsal epidermis, a tissue critically involved in dorsal closure.



The dynamic expression of extraembryonic marker genes in the beetle Tribolium castaneum reveals the complexity of serosa and amnion formation in a short germ insect

Rahul Sharma, Anke Beermann & Reinhard Schröder


Gene Expr Patterns 13(8):362-371

doi: 10.1016/j.gep.2013.07.002. 



Most insect embryos develop with two distinct extraembryonic membranes, the serosa and the amnion. In the insect beetle Tribolium the early origin of the serosa within the anterior blastoderm is well established but the origin of the amnion is still debated. It is not known whether this tissue develops from a blastodermal precursor or originates de novo later from embryonic tissue during embryogenesis. We undertook an in-depth analysis of the spatio-temporal expression pattern profile of important extraembryonic membrane marker genes with emphasis on early blastoderm development in Tribolium. The amnion marker iroquois (Tc-iro) was found co-expressed with the serosa marker zerknüllt1 (Tc-zen1) during early blastoderm formation in an anterior cap domain. This domain later resolved into two adjacent domains that likely represent the precursors of theserosa and the amnion. In addition, we found the hindsight ortholog in Tribolium (Tc-hnt) to be aserosa-specific marker. Surprisingly, decapentaplegic (Tc-dpp) expression was not seen as a symmetric cap domain but detected asymmetrically first along the DV- and later also along the AP-axis. Moreover, we found a previously undescribed domain of phosphorylated MAD (pMAD) protein in anterior ventral serosal cells. This is the first study showing that the anterior-lateral part of the amnion originates from the anterior blastoderm while the precursor of the dorsal amnion develops later de novo from a dorsal-posterior region within the differentiated blastoderm. 




Beermann A, Prühs R, Lutz R & Schröder R

A context-dependent combination of Wnt receptors controls axis elongation and leg development in a short germ insect

Development 138, 2793-2805



Short germ embryos elongate their primary body axis by consecutively adding segments from a posteriorly located growth zone. Wnt signalling is required for axis elongation in short germ arthropods, including Tribolium castaneum, but the precise functions of the different Wnt receptors involved in this process are unclear. We analysed the individual and combinatorial functions of the three Wnt receptors, Frizzled-1 (Tc-Fz1), Frizzled-2 (Tc-Fz2) and Frizzled-4 (Tc-Fz4), and their co-receptor Arrow (Tc-Arr) in the beetle Tribolium. Knockdown of gene function and expression analyses revealed that Frizzled-dependent Wnt signalling occurs anteriorly in the growth zone in the presegmental region (PSR). We show that simultaneous functional knockdown of the Wnt receptors Tc-fz1 and Tc-fz2 via RNAi resulted in collapse of the growth zone and impairment of embryonic axis elongation. Although posterior cells of the growth zone were not completely abolished, Wnt signalling within the PSR controls axial elongation at the level of pair-rule patterning, Wnt5 signalling and FGF signalling. These results identify the PSR in Tribolium as an integral tissue required for the axial elongation process, reminiscent of the presomitic mesoderm in vertebrates. Knockdown of Tc-fz1 alone interfered with the formation of the proximo-distal and the dorso-ventral axes during leg development, whereas no effect was observed with single Tc-fz2 or Tc-fz4 RNAi knockdowns. We identify Tc-Arr as an obligatory Wnt co-receptor for axis elongation, leg distalisation and segmentation. We discuss how Wnt signalling is regulated at the receptor and co-receptor levels in a dose-dependent fashion.



The Tribolium Genome Sequencing Consortium. The genome of the model beetle and pest Tribolium castaneum. Nature 452, 949-55 (= Nature-Article; R Schröder: one of 12 coordinators; focus: developmental biology).


Beermann A & Schröder R  Sites of Fgf signalling and perception during embryogenesis of the beetle Tribolium castaneum. Dev Genes Evol 218, 153-167


Berns N, Kusch T, Schröder R & Reuter R Expression, function and regulation of Brachyenteron in the short germband insect Tribolium castaneum Dev Genes Evol 218, 169-179


Bolognesi R, Beermann A, Farzana L, Wittkopp N, Lutz R, Balavoine G Brown S & Schröder R Tribolium Wnts: evidence for a larger repertoire in insects with overlapping expression patterns that suggest multiple redundant functions in embryogenesis. Dev Genes Evol 218, 193-202



Wyder S, Kriventseva E, Schröder R, Kadowaki T & Zdobnov EM Quantification of ortholog losses in insects and vertebrates. Genome Biol. 16, R242 


Schröder R vasa mRNA accumulates at the posterior pole during blastoderm formation in the flour beetle Tribolium castaneum. Dev Genes Evol 216, 277 – 283


Schoppmeier M & Schröder R Maternal Torso-signaling controls body axis elongation in a short germ insect. Curr Biol 15, 2131-2136

Cerny AC, Bucher G, Schröder R & Klingler M Breakdown of abdominal patterning in the Tribolium Krüppel mutant jaws. Development 132, 5353-5363




Copf T, Schröder R & Averof M An ancestral role of caudal genes in axis elongation and segmentation. Proc Natl Acad Sci U S A, 17711 – 17715


Beermann A, Aranda M & Schröder R The Sp8 zinc-finger transcription factor is involved in allometric growth of the limbs in the beetle Tribolium castaneum. Development 131, 733-742


Beermann A & Schröder R Functional stability of the aristaless gene in appendage tip formation during evolution. Dev Genes Evol 214, 303-308




Schröder R 2003 The genes orthodenticle and hunchback substitute for bicoid in the beetle Tribolium. Nature 422, 621 – 625

< 2003

Schröder R, Eckert C, Wolff C & Tautz D 2000 Conserved and divergent aspects of terminal patterning in the beetle Tribolium castaneum. Proc Natl Acad Sci U S A 97, 6591 – 6596


Schröder R, Jay DG & Tautz D 1999 Elimination of EVE protein by CALI in the short germ band insect Tribolium suggests a conserved pair-rule function for even-skipped. Mech. Dev 80, 191-195


Wolff C, Schröder R, Schulz C, Tautz D & Klingler M 1998 Regulation of the Tribolium homologues of caudal and hunchback in Drosophila: evidence for maternal gradient systems in a short germ embryo. Development 125, 3645 – 3654


Schulz C, Schröder R, Hausdorff B, Wolff C & Tautz D 1998 A caudal homologue in the short germ band beetle Tribolium shows similarities to both, the Drosophila and the vertebrate caudal expression patterns. Dev Genes Evol 208, 283 – 289


Schröder R, Tautz D & Jay DG 1996 Chromophore-assisted laser inactivation of even-skipped in Drosophila precisely phenocopies genetic loss of function. Dev. Genes Evol. 206, 86-88


Falciani F, Hausdorf B, Schröder R, Akam M, Tautz D, Denell R & Brown S 1996 Class 3 Hox genes in insects and the origin of zen. Proc. Natl. Acad. Sci. USA 93, 8479-8484


Wolff C, Sommer R, Schröder R, Glaser G & Tautz D 1995 Conserved and divergent expression aspects of the Drosophila segmentation gene hunchback in the short germ band embryo of the flour beetle Tribolium. Development 121, 4227-4236


Schröder R & Sander K 1993 A comparison of transplantable bicoid activity and partial bicoid homeobox sequences in several Drosophila and blowfly species (Calliphoridae). Roux' s Arch. Dev. Biol., 34-43