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E L Jockusch

Publications and source records attributed to E L Jockusch.

5 recordsLinked to original sources
PubMed2000

Phylogenetic analysis of the Wnt gene family and discovery of an arthropod wnt-10 orthologue.

Wnt genes encode a conserved family of secreted signaling proteins that play many roles in arthropod and vertebrate development. We have investigated both the phylogenetic history and molecular evolution of this gene family. We have identified a novel Wnt gene in a diversity of arthropods that it is likely an orthologue of the vertebrate Wnt-10 group. Wnt-10 is one of only two cases in which orthology between protostome and deuterostome genes could be consistently assigned based on our analyses. Despite difficulties in assessing orthologies, all of our trees suggest that the most recent common ancestor of protostomes and deuterostomes possessed more than the five Wnt genes known from either arthropods or nematodes. This suggests that Wnt gene loss has occurred during protostome evolution. In addition, we examined the rate of amino acid evolution in the two arthropod/deuterostome orthology groups we identified. We found little rate variation across taxa, with the exception that Drosophila Wnt-1 is evolving more rapidly than all vertebrate and most arthropod orthologues.

Amino Acid Sequence↗
PubMed2000

Leg development in flies versus grasshoppers: differences in dpp expression do not lead to differences in the expression of downstream components of the leg patterning pathway.

All insect legs are structurally similar, characterized by five primary segments. However, this final form is achieved in different ways. Primitively, the legs developed as direct outgrowths of the body wall, a condition retained in most insect species. In some groups, including the lineage containing the genus Drosophila, legs develop indirectly from imaginal discs. Our understanding of the molecular mechanisms regulating leg development is based largely on analysis of this derived mode of leg development in the species D. melanogaster. The current model for Drosophila leg development is divided into two phases, embryonic allocation and imaginal disc patterning, which are distinguished by interactions among the genes wingless (wg), decapentaplegic (dpp) and distalless (dll). In the allocation phase, dll is activated by wg but repressed by dpp. During imaginal disc patterning, dpp and wg cooperatively activate dll and also indirectly inhibit the nuclear localization of Extradenticle (Exd), which divide the leg into distal and proximal domains. In the grasshopper Schistocerca americana, the early expression pattern of dpp differs radically from the Drosophila pattern, suggesting that the genetic interactions that allocate the leg differ between the two species. Despite early differences in dpp expression, wg, Dll and Exd are expressed in similar patterns throughout the development of grasshopper and fly legs, suggesting that some aspects of proximodistal (P/D) patterning are evolutionarily conserved. We also detect differences in later dpp expression, which suggests that dpp likely plays a role in limb segmentation in Schistocerca, but not in Drosophila. The divergence in dpp expression is surprising given that all other comparative data on gene expression during insect leg development indicate that the molecular pathways regulating this process are conserved. However, it is consistent with the early divergence in developmental mode between fly and grasshopper limbs.

Animals↗
PubMedDate not supplied

Hypothesis testing in evolutionary developmental biology: a case study from insect wings.

Developmental data have the potential to give novel insights into morphological evolution. Because developmental data are time-consuming to obtain, support for hypotheses often rests on data from only a few distantly related species. Similarities between these distantly related species are parsimoniously inferred to represent ancestral aspects of development. However, with limited taxon sampling, ancestral similarities in developmental patterning can be difficult to distinguish from similarities that result from convergent co-option of developmental networks, which appears to be common in developmental evolution. Using a case study from insect wings, we discuss how these competing explanations for similarity can be evaluated. Two kinds of developmental data have recently been used to support the hypothesis that insect wings evolved by modification of limb branches that were present in ancestral arthropods. This support rests on the assumption that aspects of wing development in Drosophila, including similarities to crustacean epipod patterning, are ancestral for winged insects. Testing this assumption requires comparisons of wing development in Drosophila and other winged insects. Here we review data that bear on this assumption, including new data on the functions of wingless and decapentaplegic during appendage allocation in the red flour beetle Tribolium castaneum.

Animals↗