In dieser Doktorarbeit wurden verschiedene Methoden angewandt um ein besseres Verständnis der Ins... more In dieser Doktorarbeit wurden verschiedene Methoden angewandt um ein besseres Verständnis der Insektenkopfentwicklung zu erlangen. Als Modellorganismus wurde der Rotbraune Reismehlkäfer Tribolium castaneum ausgewählt. Dieser Organismus ist für die Analyse dieses Prozesses gut geeignet, da Larven von Tribolium im Gegensatz zu Drosophilalarven einen Insektentypischen Kopf mit allen Kopfanhängen aufweisen. Erstens habe ich eine Karte des Kopfhärchenmusters erstellt, das als Marker für Kopfdefekte dient. Zweitens habe ich die so genannten Kopf-Lücken-Gene orthodenticle, empty spiracles und buttonhead in Tribolium analysiert. Es ist bekannt, dass diese Gene eine wichtige Rolle in der Kopfentwicklung bei Drosophila spielen. Ich habe das Expressionsmuster und den Phänotyp, der durch den knock down mittels RNA Interferenz verursacht wurde analysiert und mit den Drosophila Daten verglichen. Dabei wurde herausgefunden, dass abhängig von der Injektionszeit der dsRNA zwei Funktionen von Tc-orth...
Tc-knirps plays different roles in the specification of antennal and mandibular parasegment bound... more Tc-knirps plays different roles in the specification of antennal and mandibular parasegment boundaries and is regulated by a pair-rule gene in the beetle Tribolium castaneum Peel et al. Peel et al. BMC Developmental Biology 2013, 13:25
Analysis of Tribolium head patterning by forward and reverse genetics and transgenic techniques D... more Analysis of Tribolium head patterning by forward and reverse genetics and transgenic techniques Dissertation submitted in partial fulfillment of the requirements for the degree of “Doctor rerum naturalium”
Research article Large-scale insertional mutagenesis of a coleopteran stored grain pest, the red ... more Research article Large-scale insertional mutagenesis of a coleopteran stored grain pest, the red flour beetle Tribolium castaneum, identifies embryonic lethal mutations and enhancer traps
Background: The red flour beetle Tribolium castaneum has developed into an insect model system se... more Background: The red flour beetle Tribolium castaneum has developed into an insect model system second only to Drosophila. Moreover, as a coleopteran it represents the most species-rich metazoan taxon which also includes many pest species. The genetic toolbox for Tribolium research has expanded in the past years but spatio-temporally controlled misexpression of genes has not been possible so far. Results: Here we report the establishment of the GAL4/UAS binary expression system in Tribolium castaneum. Both GAL4Δ and GAL4VP16 driven by the endogenous heat shock inducible promoter of the Tribolium hsp68 gene are efficient in activating reporter gene expression under the control of the Upstream Activating Sequence (UAS). UAS driven ubiquitous tGFP fluorescence was observed in embryos within four hours after activation while in-situ hybridization against tGFP revealed expression already after two hours. The response is quick in relation to the duration of embryonic development in Triboli...
Clonal marking techniques based on the Cre/lox and Flp/FRT systems are widely used in multicellul... more Clonal marking techniques based on the Cre/lox and Flp/FRT systems are widely used in multicellular model organisms to mark individual cells and their progeny, in order to study their morphology, growth properties and developmental fates. The same tools can be adapted to introduce specific genetic changes in a subset of cells within the body, i.e. to perform mosaic genetic analysis. Marking and manipulating distinct cell clones requires control over the frequency of clone induction, which is sometimes difficult to achieve. Here we present Valcyrie, a new method that replaces the conventional Cre or Flp recombinase-mediated excision of a marker cassette by CRISPR-mediated excision. A major advantage of this approach is that CRISPR efficiency can be tuned in a predictable fashion by manipulating the degree of sequence complementarity between the CRISPR guide RNA and its targets. We establish the method in the beetle Tribolium castaneum. We demonstrate that clone marking frequency can ...
Gene editing techniques are revolutionizing the way we conduct genetics in many organisms. The CR... more Gene editing techniques are revolutionizing the way we conduct genetics in many organisms. The CRISPR/Cas nuclease has emerged as a highly versatile, efficient and affordable tool for targeting chosen sites in the genome. Beyond its applications in established model organisms, CRISPR technology provides a platform for genetic intervention in a wide range of species, limited only by our ability to deliver it to cells and to select mutations efficiently. Here we test the CRISPR technology in an emerging insect model and pest, the beetle Tribolium castaneum. We use simple assays to test CRISPR/Cas activity, we demonstrate efficient expression of guide RNAs and Cas9 from Tribolium U6 and hsp68 promoters and we test the efficiency of knock-out and knock-in approaches in Tribolium. We find that 55-80% of injected individuals carry mutations (indels) generated by non-homologous end joining, including mosaic bi-allelic knock-outs; 71-100% carry such mutations in their germline and transmit ...
Highlights d A gradient of BMP signaling maintains the directive axis in Nematostella d BMP signa... more Highlights d A gradient of BMP signaling maintains the directive axis in Nematostella d BMP signaling regulates Nematostella Hox genes and patterns the endoderm d BMP network topology is similar in Nematostella and Xenopus d Constraint analysis reveals the evolvability of BMP network components Authors
INTRODUCTIONThe red flour beetle, Tribolium castaneum, has emerged as an important model system f... more INTRODUCTIONThe red flour beetle, Tribolium castaneum, has emerged as an important model system for studying the evolution of development. Studies with Tribolium complement the vast amount of research done with Drosophila. Developmental features that are conserved between Drosophila and Tribolium, such as body segmentation, are achieved by quite different means, and thus comparison of developmental mechanisms between these two insects can address many interesting questions concerning the evolution of morphology and other characters. Most in situ protocols used for Tribolium have been adapted from Drosophila studies. Whole-mount in situ hybridization is a standard technique to visualize the activity of genes in embryos. The single and double staining protocol presented here uses two nonfluorescent stains to reveal gene activity. The development of both stains can be monitored visually, allowing the strength of the signal to be adjusted as needed. Cells that express both of the genes under investigation are readily detected using a microscope. The use of EGTA during fixation increases the proportion of embryos that devitellinize upon methanol treatment.
Background: Non-traditional model systems need new tools that will enable them to enter the field... more Background: Non-traditional model systems need new tools that will enable them to enter the field of functional genetics. These tools should enable the exploration of gene function, via knock-downs of endogenous genes, as well as overexpression and ectopic expression of transgenes. Methodology: We constructed a new vector called Pogostick that can be used to over-express or down-regulate genes in organisms amenable to germ line transformation by the piggyBac transposable element. Pogostick can be found at www. addgene.org, a non-profit plasmid repository. The vector currently uses the heat-shock promoter Hsp70 from Drosophila to drive transgene expression and, as such, will have immediate applicability to organisms that can correctly interpret this promotor sequence. We detail how to clone candidate genes into this vector and test its functionality in Drosophila by targeting a gene coding for the fluorescent protein DsRed. By cloning a single DsRed copy into the vector, and generating transgenic lines, we show that DsRed mRNA and protein levels are elevated following heat-shock. When cloning a second copy of DsRed in reverse orientation into a flanking site, and transforming flies constitutively expressing DsRed in the eyes, we show that endogenous mRNA and protein levels drop following heat-shock. We then test the over-expression vector, containing the complete cDNA of Ultrabithorax (Ubx) gene, in an emerging model system, Bicyclus anynana. We produce a transgenic line and show that levels of Ubx mRNA expression rise significantly following a heat-shock. Finally, we show how to obtain genomic sequence adjacent to the Pogostick insertion site and to estimate transgene copy number in genomes of transformed individuals. Significance: This new vector will allow emerging model systems to enter the field of functional genetics with few hurdles.
For homeotic and segment-polarity genes in Drosophila, a switch in gene regulation has been descr... more For homeotic and segment-polarity genes in Drosophila, a switch in gene regulation has been described that distinguishes patterning and maintenance phases. Maintenance of segment and organ primordia involves secondary patterning and differentiation steps, as well as survival factors regulating proliferation and organ size. In a screen for embryonic lethal mutations in the flour beetle Tribolium castaneum, we have recovered two alleles of the knödel gene, which result in short, bag-like embryos. These embryos have severely reduced appendages and differentiate a cuticle that lacks most overt signs of segmentation. In addition, they lack bristles and display defects in the nervous system. Early patterning in knödel mutant embryos is normal up to the extended germ band stage, as indicated by the formation of regular even-skipped (Tc'eve) and wingless (Tc'wg) stripes. Afterwards, however, these patterns degenerate. Similarly, proximo-distal growth and patterning of limbs are nearly normal initially, but limb primordia shrink, and proximo-distal patterns degenerate, during subsequent stages. knödel could be a segment polarity gene required for segment border maintenance in both trunk and appendages. Alternatively, it may have a more general role in tissue or organ maintenance.
Tribolium castaneum is a member of the most species-rich eukaryotic order, a powerful model organ... more Tribolium castaneum is a member of the most species-rich eukaryotic order, a powerful model organism for the study of generalized insect development, and an important pest of stored agricultural products. We describe its genome sequence here. This omnivorous beetle has evolved the ability to interact with a diverse chemical environment, as shown by large expansions in odorant and gustatory receptors, as well as P450 and other detoxification enzymes. Development in Tribolium is more representative of other insects than is Drosophila, a fact reflected in gene content and function. For example, Tribolium has retained more ancestral genes involved in cell-cell communication than Drosophila, some being expressed in the growth zone crucial for axial elongation in short-germ development. Systemic RNA interference in T. castaneum functions differently from that in Caenorhabditis elegans, but nevertheless offers similar power for the elucidation of gene function and identification of targets...
Despite considerable differences in morphology and complexity of body plans among animals, a grea... more Despite considerable differences in morphology and complexity of body plans among animals, a great part of the gene set is shared among Bilateria and their basally branching sister group, the Cnidaria. This suggests that the common ancestor of eumetazoans already had a highly complex gene repertoire. At present it is therefore unclear how morphological diversification is encoded in the genome. Here we address the possibility that differences in gene regulation could contribute to the large morphological divergence between cnidarians and bilaterians. To this end, we generated the first genome-wide map of gene regulatory elements in a nonbilaterian animal, the sea anemone Nematostella vectensis. Using chromatin immunoprecipitation followed by deep sequencing of five chromatin modifications and a transcriptional cofactor, we identified over 5000 enhancers in the Nematostella genome and could validate 75% of the tested enhancers in vivo. We found that in Nematostella, but not in yeast, ...
The head gap genes orthodenticle (otd), empty spiracles (ems) and buttonhead (btd) are required f... more The head gap genes orthodenticle (otd), empty spiracles (ems) and buttonhead (btd) are required for metamerization and segment specification in Drosophila. We asked whether the function of their orthologs is conserved in the red flour beetle Tribolium castaneum which in contrast to Drosophila develops its larval head in a way typical for insects. We find that depending on dsRNA injection time, two functions of Tc-orthodenticle1 (Tc-otd1) can be identified. The early regionalization function affects all segments formed during the blastoderm stage while the later head patterning function is similar to Drosophila. In contrast, both expression and function of Tc-empty spiracles (Tc-ems) are restricted to the posterior part of the ocular and the anterior part of the antennal segment and Tc-buttonhead (Tc-btd) is not required for head cuticle formation at all. We conclude that the gap gene like roles of ems and btd are not conserved while at least the head patterning function of otd appears to be similar in fly and beetle. Hence, the ancestral mode of insect head segmentation remains to be discovered. With this work, we establish Tribolium as a model system for arthropod head development that does not suffer from the Drosophila specific problems like head involution and strongly reduced head structures.
The genetic control of leg development is well characterized in the fly Drosophila melanogaster. ... more The genetic control of leg development is well characterized in the fly Drosophila melanogaster. These control mechanisms, however, must differ to some degree between different insect species to account for the morphological diversity of thoracic legs in the insects. The legs of the flour beetle Tribolium castaneum differ from the Drosophila legs in their developmental mode as well as in their specific morphology especially at the larval stage. In order to identify genes involved in the morphogenesis of the Tribolium larval legs, we have analyzed EGFP enhancer trap lines of Tribolium. We have identified the zfh2 gene as a novel factor required for normal leg development in Tribolium. RNA interference with zfh2 function leads to two alternative classes of leg phenotype. The loss of a leg segment boundary and the generation of ectopic outgrowths in one class of phenotype suggest a role in leg segmentation and segment growth. The malformation of the pretarsal claw in the second class of phenotype suggests a role in distal development and the morphogenesis of the claw-shaped morphology of the pretarsus. This suggests that zfh2 is involved in the regulation of an unidentified target gene in a concentration-dependent manner. Our results demonstrate that enhancer trap screens in T. castaneum have the potential to identify novel gene functions regulating specific developmental processes.
Your article is protected by copyright and all rights are held exclusively by Springer-Verlag. Th... more Your article is protected by copyright and all rights are held exclusively by Springer-Verlag. This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your work, please use the accepted author's version for posting to your own website or your institution's repository. You may further deposit the accepted author's version on a funder's repository at a funder's request, provided it is not made publicly available until 12 months after publication.
Background The Drosophila larval head is evolutionarily derived at the genetic and morphological ... more Background The Drosophila larval head is evolutionarily derived at the genetic and morphological level. In the beetle Tribolium castaneum, development of the larval head more closely resembles the ancestral arthropod condition. Unlike in Drosophila, a knirps homologue (Tc-kni) is required for development of the antennae and mandibles. However, published Tc-kni data are restricted to cuticle phenotypes and Tc-even-skipped and Tc-wingless stainings in knockdown embryos. Hence, it has remained unclear whether the entire antennal and mandibular segments depend on Tc-kni function, and whether the intervening intercalary segment is formed completely. We address these questions with a detailed examination of Tc-kni function. Results By examining the expression of marker genes in RNAi embryos, we show that Tc-kni is required only for the formation of the posterior parts of the antennal and mandibular segments (i.e. the parasegmental boundaries). Moreover, we find that the role of Tc-kni is ...
In dieser Doktorarbeit wurden verschiedene Methoden angewandt um ein besseres Verständnis der Ins... more In dieser Doktorarbeit wurden verschiedene Methoden angewandt um ein besseres Verständnis der Insektenkopfentwicklung zu erlangen. Als Modellorganismus wurde der Rotbraune Reismehlkäfer Tribolium castaneum ausgewählt. Dieser Organismus ist für die Analyse dieses Prozesses gut geeignet, da Larven von Tribolium im Gegensatz zu Drosophilalarven einen Insektentypischen Kopf mit allen Kopfanhängen aufweisen. Erstens habe ich eine Karte des Kopfhärchenmusters erstellt, das als Marker für Kopfdefekte dient. Zweitens habe ich die so genannten Kopf-Lücken-Gene orthodenticle, empty spiracles und buttonhead in Tribolium analysiert. Es ist bekannt, dass diese Gene eine wichtige Rolle in der Kopfentwicklung bei Drosophila spielen. Ich habe das Expressionsmuster und den Phänotyp, der durch den knock down mittels RNA Interferenz verursacht wurde analysiert und mit den Drosophila Daten verglichen. Dabei wurde herausgefunden, dass abhängig von der Injektionszeit der dsRNA zwei Funktionen von Tc-orth...
Tc-knirps plays different roles in the specification of antennal and mandibular parasegment bound... more Tc-knirps plays different roles in the specification of antennal and mandibular parasegment boundaries and is regulated by a pair-rule gene in the beetle Tribolium castaneum Peel et al. Peel et al. BMC Developmental Biology 2013, 13:25
Analysis of Tribolium head patterning by forward and reverse genetics and transgenic techniques D... more Analysis of Tribolium head patterning by forward and reverse genetics and transgenic techniques Dissertation submitted in partial fulfillment of the requirements for the degree of “Doctor rerum naturalium”
Research article Large-scale insertional mutagenesis of a coleopteran stored grain pest, the red ... more Research article Large-scale insertional mutagenesis of a coleopteran stored grain pest, the red flour beetle Tribolium castaneum, identifies embryonic lethal mutations and enhancer traps
Background: The red flour beetle Tribolium castaneum has developed into an insect model system se... more Background: The red flour beetle Tribolium castaneum has developed into an insect model system second only to Drosophila. Moreover, as a coleopteran it represents the most species-rich metazoan taxon which also includes many pest species. The genetic toolbox for Tribolium research has expanded in the past years but spatio-temporally controlled misexpression of genes has not been possible so far. Results: Here we report the establishment of the GAL4/UAS binary expression system in Tribolium castaneum. Both GAL4Δ and GAL4VP16 driven by the endogenous heat shock inducible promoter of the Tribolium hsp68 gene are efficient in activating reporter gene expression under the control of the Upstream Activating Sequence (UAS). UAS driven ubiquitous tGFP fluorescence was observed in embryos within four hours after activation while in-situ hybridization against tGFP revealed expression already after two hours. The response is quick in relation to the duration of embryonic development in Triboli...
Clonal marking techniques based on the Cre/lox and Flp/FRT systems are widely used in multicellul... more Clonal marking techniques based on the Cre/lox and Flp/FRT systems are widely used in multicellular model organisms to mark individual cells and their progeny, in order to study their morphology, growth properties and developmental fates. The same tools can be adapted to introduce specific genetic changes in a subset of cells within the body, i.e. to perform mosaic genetic analysis. Marking and manipulating distinct cell clones requires control over the frequency of clone induction, which is sometimes difficult to achieve. Here we present Valcyrie, a new method that replaces the conventional Cre or Flp recombinase-mediated excision of a marker cassette by CRISPR-mediated excision. A major advantage of this approach is that CRISPR efficiency can be tuned in a predictable fashion by manipulating the degree of sequence complementarity between the CRISPR guide RNA and its targets. We establish the method in the beetle Tribolium castaneum. We demonstrate that clone marking frequency can ...
Gene editing techniques are revolutionizing the way we conduct genetics in many organisms. The CR... more Gene editing techniques are revolutionizing the way we conduct genetics in many organisms. The CRISPR/Cas nuclease has emerged as a highly versatile, efficient and affordable tool for targeting chosen sites in the genome. Beyond its applications in established model organisms, CRISPR technology provides a platform for genetic intervention in a wide range of species, limited only by our ability to deliver it to cells and to select mutations efficiently. Here we test the CRISPR technology in an emerging insect model and pest, the beetle Tribolium castaneum. We use simple assays to test CRISPR/Cas activity, we demonstrate efficient expression of guide RNAs and Cas9 from Tribolium U6 and hsp68 promoters and we test the efficiency of knock-out and knock-in approaches in Tribolium. We find that 55-80% of injected individuals carry mutations (indels) generated by non-homologous end joining, including mosaic bi-allelic knock-outs; 71-100% carry such mutations in their germline and transmit ...
Highlights d A gradient of BMP signaling maintains the directive axis in Nematostella d BMP signa... more Highlights d A gradient of BMP signaling maintains the directive axis in Nematostella d BMP signaling regulates Nematostella Hox genes and patterns the endoderm d BMP network topology is similar in Nematostella and Xenopus d Constraint analysis reveals the evolvability of BMP network components Authors
INTRODUCTIONThe red flour beetle, Tribolium castaneum, has emerged as an important model system f... more INTRODUCTIONThe red flour beetle, Tribolium castaneum, has emerged as an important model system for studying the evolution of development. Studies with Tribolium complement the vast amount of research done with Drosophila. Developmental features that are conserved between Drosophila and Tribolium, such as body segmentation, are achieved by quite different means, and thus comparison of developmental mechanisms between these two insects can address many interesting questions concerning the evolution of morphology and other characters. Most in situ protocols used for Tribolium have been adapted from Drosophila studies. Whole-mount in situ hybridization is a standard technique to visualize the activity of genes in embryos. The single and double staining protocol presented here uses two nonfluorescent stains to reveal gene activity. The development of both stains can be monitored visually, allowing the strength of the signal to be adjusted as needed. Cells that express both of the genes under investigation are readily detected using a microscope. The use of EGTA during fixation increases the proportion of embryos that devitellinize upon methanol treatment.
Background: Non-traditional model systems need new tools that will enable them to enter the field... more Background: Non-traditional model systems need new tools that will enable them to enter the field of functional genetics. These tools should enable the exploration of gene function, via knock-downs of endogenous genes, as well as overexpression and ectopic expression of transgenes. Methodology: We constructed a new vector called Pogostick that can be used to over-express or down-regulate genes in organisms amenable to germ line transformation by the piggyBac transposable element. Pogostick can be found at www. addgene.org, a non-profit plasmid repository. The vector currently uses the heat-shock promoter Hsp70 from Drosophila to drive transgene expression and, as such, will have immediate applicability to organisms that can correctly interpret this promotor sequence. We detail how to clone candidate genes into this vector and test its functionality in Drosophila by targeting a gene coding for the fluorescent protein DsRed. By cloning a single DsRed copy into the vector, and generating transgenic lines, we show that DsRed mRNA and protein levels are elevated following heat-shock. When cloning a second copy of DsRed in reverse orientation into a flanking site, and transforming flies constitutively expressing DsRed in the eyes, we show that endogenous mRNA and protein levels drop following heat-shock. We then test the over-expression vector, containing the complete cDNA of Ultrabithorax (Ubx) gene, in an emerging model system, Bicyclus anynana. We produce a transgenic line and show that levels of Ubx mRNA expression rise significantly following a heat-shock. Finally, we show how to obtain genomic sequence adjacent to the Pogostick insertion site and to estimate transgene copy number in genomes of transformed individuals. Significance: This new vector will allow emerging model systems to enter the field of functional genetics with few hurdles.
For homeotic and segment-polarity genes in Drosophila, a switch in gene regulation has been descr... more For homeotic and segment-polarity genes in Drosophila, a switch in gene regulation has been described that distinguishes patterning and maintenance phases. Maintenance of segment and organ primordia involves secondary patterning and differentiation steps, as well as survival factors regulating proliferation and organ size. In a screen for embryonic lethal mutations in the flour beetle Tribolium castaneum, we have recovered two alleles of the knödel gene, which result in short, bag-like embryos. These embryos have severely reduced appendages and differentiate a cuticle that lacks most overt signs of segmentation. In addition, they lack bristles and display defects in the nervous system. Early patterning in knödel mutant embryos is normal up to the extended germ band stage, as indicated by the formation of regular even-skipped (Tc'eve) and wingless (Tc'wg) stripes. Afterwards, however, these patterns degenerate. Similarly, proximo-distal growth and patterning of limbs are nearly normal initially, but limb primordia shrink, and proximo-distal patterns degenerate, during subsequent stages. knödel could be a segment polarity gene required for segment border maintenance in both trunk and appendages. Alternatively, it may have a more general role in tissue or organ maintenance.
Tribolium castaneum is a member of the most species-rich eukaryotic order, a powerful model organ... more Tribolium castaneum is a member of the most species-rich eukaryotic order, a powerful model organism for the study of generalized insect development, and an important pest of stored agricultural products. We describe its genome sequence here. This omnivorous beetle has evolved the ability to interact with a diverse chemical environment, as shown by large expansions in odorant and gustatory receptors, as well as P450 and other detoxification enzymes. Development in Tribolium is more representative of other insects than is Drosophila, a fact reflected in gene content and function. For example, Tribolium has retained more ancestral genes involved in cell-cell communication than Drosophila, some being expressed in the growth zone crucial for axial elongation in short-germ development. Systemic RNA interference in T. castaneum functions differently from that in Caenorhabditis elegans, but nevertheless offers similar power for the elucidation of gene function and identification of targets...
Despite considerable differences in morphology and complexity of body plans among animals, a grea... more Despite considerable differences in morphology and complexity of body plans among animals, a great part of the gene set is shared among Bilateria and their basally branching sister group, the Cnidaria. This suggests that the common ancestor of eumetazoans already had a highly complex gene repertoire. At present it is therefore unclear how morphological diversification is encoded in the genome. Here we address the possibility that differences in gene regulation could contribute to the large morphological divergence between cnidarians and bilaterians. To this end, we generated the first genome-wide map of gene regulatory elements in a nonbilaterian animal, the sea anemone Nematostella vectensis. Using chromatin immunoprecipitation followed by deep sequencing of five chromatin modifications and a transcriptional cofactor, we identified over 5000 enhancers in the Nematostella genome and could validate 75% of the tested enhancers in vivo. We found that in Nematostella, but not in yeast, ...
The head gap genes orthodenticle (otd), empty spiracles (ems) and buttonhead (btd) are required f... more The head gap genes orthodenticle (otd), empty spiracles (ems) and buttonhead (btd) are required for metamerization and segment specification in Drosophila. We asked whether the function of their orthologs is conserved in the red flour beetle Tribolium castaneum which in contrast to Drosophila develops its larval head in a way typical for insects. We find that depending on dsRNA injection time, two functions of Tc-orthodenticle1 (Tc-otd1) can be identified. The early regionalization function affects all segments formed during the blastoderm stage while the later head patterning function is similar to Drosophila. In contrast, both expression and function of Tc-empty spiracles (Tc-ems) are restricted to the posterior part of the ocular and the anterior part of the antennal segment and Tc-buttonhead (Tc-btd) is not required for head cuticle formation at all. We conclude that the gap gene like roles of ems and btd are not conserved while at least the head patterning function of otd appears to be similar in fly and beetle. Hence, the ancestral mode of insect head segmentation remains to be discovered. With this work, we establish Tribolium as a model system for arthropod head development that does not suffer from the Drosophila specific problems like head involution and strongly reduced head structures.
The genetic control of leg development is well characterized in the fly Drosophila melanogaster. ... more The genetic control of leg development is well characterized in the fly Drosophila melanogaster. These control mechanisms, however, must differ to some degree between different insect species to account for the morphological diversity of thoracic legs in the insects. The legs of the flour beetle Tribolium castaneum differ from the Drosophila legs in their developmental mode as well as in their specific morphology especially at the larval stage. In order to identify genes involved in the morphogenesis of the Tribolium larval legs, we have analyzed EGFP enhancer trap lines of Tribolium. We have identified the zfh2 gene as a novel factor required for normal leg development in Tribolium. RNA interference with zfh2 function leads to two alternative classes of leg phenotype. The loss of a leg segment boundary and the generation of ectopic outgrowths in one class of phenotype suggest a role in leg segmentation and segment growth. The malformation of the pretarsal claw in the second class of phenotype suggests a role in distal development and the morphogenesis of the claw-shaped morphology of the pretarsus. This suggests that zfh2 is involved in the regulation of an unidentified target gene in a concentration-dependent manner. Our results demonstrate that enhancer trap screens in T. castaneum have the potential to identify novel gene functions regulating specific developmental processes.
Your article is protected by copyright and all rights are held exclusively by Springer-Verlag. Th... more Your article is protected by copyright and all rights are held exclusively by Springer-Verlag. This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your work, please use the accepted author's version for posting to your own website or your institution's repository. You may further deposit the accepted author's version on a funder's repository at a funder's request, provided it is not made publicly available until 12 months after publication.
Background The Drosophila larval head is evolutionarily derived at the genetic and morphological ... more Background The Drosophila larval head is evolutionarily derived at the genetic and morphological level. In the beetle Tribolium castaneum, development of the larval head more closely resembles the ancestral arthropod condition. Unlike in Drosophila, a knirps homologue (Tc-kni) is required for development of the antennae and mandibles. However, published Tc-kni data are restricted to cuticle phenotypes and Tc-even-skipped and Tc-wingless stainings in knockdown embryos. Hence, it has remained unclear whether the entire antennal and mandibular segments depend on Tc-kni function, and whether the intervening intercalary segment is formed completely. We address these questions with a detailed examination of Tc-kni function. Results By examining the expression of marker genes in RNAi embryos, we show that Tc-kni is required only for the formation of the posterior parts of the antennal and mandibular segments (i.e. the parasegmental boundaries). Moreover, we find that the role of Tc-kni is ...
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