Dataset Information

Separable stripe enhancer elements for the pair-rule gene hairy in the beetle Tribolium.

ABSTRACT: Pair-rule genes in Drosophila integrate the positional information provided by the transcription factor gradients of gap genes and set the framework for the expression of the segment polarity genes. Pair-rule genes are also expressed during the segmentation of the short germ-band embryo of the flour beetle Tribolium, although this occurs under cellular conditions that should not allow the generation of transcription factor gradients by passive diffusion. To analyse the regulation of the pair-rule gene hairy in Tribolium, we have used germline transformation with reporter gene constructs based on the piggyBac vector. We can identify an upstream fragment that drives the full expression of the eight pair-rule stripes, which are sequentially generated during embryogenesis. Further experiments with smaller fragments reveal separable regions driving stripes three to five, and one region driving stripe three only. Our results suggest that the generation of pair-rule stripes in Tribolium is comparable to that in Drosophila despite the cellular versus syncytial mode of embryogenesis.

SUBMITTER: Eckert C

PROVIDER: S-EPMC1299068 | biostudies-literature | 2004 Jun

REPOSITORIES: biostudies-literature

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Separable stripe enhancer elements for the pair-rule gene hairy in the beetle Tribolium.

Eckert Christoph C Aranda Manuel M Wolff Christian C Tautz Diethard D

EMBO reports 20040507 6

Pair-rule genes in Drosophila integrate the positional information provided by the transcription factor gradients of gap genes and set the framework for the expression of the segment polarity genes. Pair-rule genes are also expressed during the segmentation of the short germ-band embryo of the flour beetle Tribolium, although this occurs under cellular conditions that should not allow the generation of transcription factor gradients by passive diffusion. To analyse the regulation of the pair-rul ...[more]

PMID: 15133480

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Project description:BackgroundThe 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.ResultsBy 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 distinct in these segments: Tc-kni is required for the initiation of the antennal parasegment boundary, but only for the maintenance of the mandibular parasegmental boundary. Surprisingly, Tc-kni controls the timing of expression of the Hox gene Tc-labial in the intercalary segment, although this segment does form in the absence of Tc-kni function. Unexpectedly, we find that the pair-rule gene Tc-even-skipped helps set the posterior boundary of Tc-kni expression in the mandible. Using the mutant antennaless, a likely regulatory Null mutation at the Tc-kni locus, we provide evidence that our RNAi studies represent a Null situation.ConclusionsTc-kni is required for the initiation of the antennal and the maintenance of the mandibular parasegmental boundaries. Tc-kni is not required for specification of the anterior regions of these segments, nor the intervening intercalary segment, confirming that Tc-kni is not a canonical 'gap-gene'. Our finding that a gap gene orthologue is regulated by a pair rule gene adds to the view that the segmentation gene hierarchies differ between Tribolium and Drosophila upstream of the pair rule gene level. In Tribolium, as in Drosophila, head and trunk segmentation gene networks cooperate to pattern the mandibular segment, albeit involving Tc-kni as novel component.

Project description:The beetle Tribolium castaneum has increasingly become a powerful model for comparative research on insect development. One recent resource is a collection of piggyBac transposon-based enhancer trap lines. Here, we provide a detailed analysis of three selected lines and demonstrate their value for investigations in the second half of embryogenesis, which has thus far lagged behind research on early stages. Two lines, G12424 and KT650, show enhanced green fluorescent protein (EGFP) expression throughout the extraembryonic serosal tissue and in a few discrete embryonic domains. Intriguingly, both lines show for the first time a degree of regionalization within the mature serosa. However, their expression profiles illuminate distinct aspects of serosal biology: G12424 tracks the tissue's rapid maturation while KT650 expression likely reflects ongoing physiological processes. The third line, G04609, is stably expressed in mesodermal domains, including segmental muscles and the heart. Genomic mapping followed by in situ hybridization for genes near to the G04609 insertion site suggests that the transposon has trapped enhancer information for the Tribolium orthologue of midline (Tc-mid). Altogether, our analyses provide the first live imaging, long-term characterizations of enhancer traps from this collection. We show that EGFP expression is readily detected, including in heterozygote crosses that permit the simultaneous visualization of multiple tissue types. The tissue specificity provides live, endogenous marker gene expression at key developmental stages that are inaccessible for whole mount staining. Furthermore, the nonlocalized EGFP in these lines illuminates both the nucleus and cytoplasm, providing cellular resolution for morphogenesis research on processes such as dorsal closure and heart formation. In future work, identification of regulatory regions driving these enhancer traps will deepen our understanding of late developmental control, including in the extraembryonic domain, which is a hallmark of insect development but which is not yet well understood.

Dataset Information

Separable stripe enhancer elements for the pair-rule gene hairy in the beetle Tribolium.

Publications

Separable stripe enhancer elements for the pair-rule gene hairy in the beetle Tribolium.

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