The role of the segmentation gene hairy in Tribolium

Hairy stripes in Tribolium are generated during blastoderm and germ band extension, but a direct role for Tc-h in trunk segmentation was not found. We have studied here several aspects of hairy function and expression in Tribolium, to further elucidate its role. First, we show that there is no functional redundancy with other hairy paralogues in Tribolium. Second, we cloned the hairy orthologue from Tribolium confusum and show that its expression mimics that of Tribolium castaneum, implying that stripe expression should be functional in some way. Third, we show that the dynamics of stripe formation in the growth zone is not compatible with an oscillatory mechanism comparable to the one driving the expression of hairy homologues in vertebrates. Fourth, we use parental RNAi experiments to study Tc-h function and we find that mandible and labium are particularly sensitive to loss of Tc-h, reminiscent of a pair-rule function in the head region. In addition, lack of Tc-h leads to cell death in the gnathal region at later embryonic stages, resulting in a detachment of the head. Cell death patterns are also altered in the midline. Finally, we have analysed the effect of Tc-h knockdown on two of the target genes of hairy in Drosophila, namely fushi tarazu and paired. We find that the trunk expression of Tc-h is required to regulate Tc-ftz, although Tc-ftz is itself also not required for trunk segmentation in Tribolium. Our results imply that there is considerable divergence in hairy function between Tribolium and Drosophila

Insertional mutagenesis screening identifies the zinc finger homeodomain 2 (zfh2) gene as a novel factor required for embryonic leg development in Tribolium castaneum

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

Genome of Diuraphis noxia, a global aphid pest of small grains

Background: The Russian wheat aphid, Diuraphis noxia Kurdjumov, is one of the most important pests of small grains throughout the temperate regions of the world. This phytotoxic aphid causes severe systemic damage symptoms in wheat, barley, and other small grains as a direct result of the salivary proteins it injects into the plant while feeding.Results: We sequenced and de novo assembled the genome of D. noxia Biotype 2, the strain most virulent to resistance genes in wheat. The assembled genomic scaffolds span 393 MB, equivalent to 93% of its 421 MB genome, and contains 19,097 genes. D. noxia has the most AT-rich insect genome sequenced to date (70.9%), with a bimodal CpG(O/E) distribution and a complete set of methylation related genes. The D. noxia genome displays a widespread, extensive reduction in the number of genes per ortholog group, including defensive, detoxification, chemosensory, and sugar transporter groups in comparison to the Acyrthosiphon pisum genome, including a 65% reduction in chemoreceptor genes. Thirty of 34 known D. noxia salivary genes were found in this assembly. These genes exhibited less homology with those salivary genes commonly expressed in insect saliva, such as glucose dehydrogenase and trehalase, yet greater conservation among genes that are expressed in D. noxia saliva but not detected in the saliva of other insects. Genes involved in insecticide activity and endosymbiont-derived genes were also found, as well as genes involved in virus transmission, although D. noxia is not a viral vector.Conclusions: This genome is the second sequenced aphid genome, and the first of a phytotoxic insect. D. noxia's reduced gene content of may reflect the influence of phytotoxic feeding in shaping the D. noxia genome, and in turn in broadening its host range. The presence of methylation-related genes, including cytosine methylation, is consistent with other parthenogenetic and polyphenic insects. The D. noxia genome will provide an important contrast to the A. pisum genome and advance functional and comparative genomics of insects and other organisms.Peer reviewedBiochemistry and Molecular Biolog