| 1. |
- Ahlberg, Per, et al.
(författare)
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Developmental plasticity and disparity in early dipnoan (lungfish) dentitions.
- 2006
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 8:4, s. 331-349
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Tidskriftsartikel (refereegranskat)abstract
- Although the lungfish (Dipnoi) belong within the Osteichthyes, their dentitions are radically different from other osteichthyans. Lungfish dentitions also show a uniquely high structural disparity during the early evolution of the group, partly owing to the independent variation of odontogenic and odontoclastic processes that are tightly and stereotypically coordinated in other osteichthyans. We present a phylogenetic analysis of early lungfishes incorporating a novel approach to coding these process characters in preference to the resultant adult dental morphology. The results only partially resolve the interrelationships of Devonian dipnoans, but show that the widely discussed hypothesis of separate tooth-plated, dentine-plated, and denticulated lineages is unlikely to be true. The dipnoan status of Diabolepis is corroborated. Lungfish dentitions seem to have undergone extensive and nonparsimonious evolution during the early history of the group, but much of the resulting disparity can be explained by a modest number of evolutionary steps in the underlying developmental processes, those for dental formation (odontogenic) and those for the remodeling of dentine tissue (odontoclastic). Later in lungfish evolution, this disparity was lost as the group settled to a pattern of dental development that is just as stereotypic as, but completely different from, that of other osteichthyans.
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| 2. |
- Damen, Wim, et al.
(författare)
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Pair rule gene orthologs in spider segmentation
- 2005
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 7:6, s. 618-628
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Tidskriftsartikel (refereegranskat)abstract
- The activation of pair rule genes is the first indication of the metameric organization of the Drosophila embryo and thus forms a key step in the segmentation process. There are two classes of pair rule genes in Drosophila: the primary pair rule genes that are directly activated by the maternal and gap genes and the secondary pair rule genes that rely on input from the primary pair rule genes. Here we analyze orthologs of Drosophila primary and secondary pair rule orthologs in the spider Cupiennius salei. The expression patterns of the spider pair rule gene orthologs can be subdivided in three groups: even-skipped and runt-1 expression is in stripes that start at the posterior end of the growth zone and their expression ends before the stripes reach the anterior end of the growth zone, while hairy and pairberry-3 stripes also start at the posterior end, but do not cease in the anterior growth zone. Stripes of odd-paired, odd-skipped-related-1, and sloppy paired are only found in the anterior portion of the growth zone. The various genes thus seem to be active during different phases of segment specification. It is notable that the spider orthologs of the Drosophila primary pair rule genes are active more posterior in the growth zone and thus during earlier phases of segment specification than most orthologs of Drosophila secondary pair rule genes, indicating that parts of the hierarchy might be conserved between flies and spiders. The spider ortholog of the Drosophila pair rule gene fushi tarazu is not expressed in the growth zone, but is expressed in a Hox-like fashion. The segmentation function of fushi tarazu thus appears to be a newly acquired role of the gene in the lineage of the mandibulate arthropods.PMID:16336415
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| 3. |
- Janssen, Ralf, et al.
(författare)
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Diverged and conserved aspects of heart formation in a spider
- 2008
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 10:2, s. 155-165
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Tidskriftsartikel (refereegranskat)abstract
- Heart development exhibits some striking similarities between vertebrates and arthropods, for example in both cases the heart develops as a linear tube from mesodermal cells. Furthermore, the underlying molecular pathways exhibit a significant number of similarities between vertebrates and the fruit fly Drosophila, suggesting a common origin of heart development in the last common ancestor of flies and vertebrates. However, there is hardly any molecular data from other animals. Here we show that many of the key genes are also active in heart development in the spider Cupiennius salei. Spiders belong to the chelicerates and are distantly related to insects with respect to the other arthropods. The tinman/Nkx2.5 ortholog is the first gene to be specifically expressed in the presumptive spider heart, like in flies and vertebrates. We also show that tinman is expressed in a similar way in the beetle Tribolium castaneum. Taken together this demonstrates that tinman has a conserved role in the specification of the arthropod heart. In addition, we analyzed the expression of other heart genes (decapentaplegic, Wnt5, H15, even-skipped, and Mef2 ) in Cupiennius. The expression of these genes suggests that the genetic pathway of heart development may be largely conserved among arthropods. However, a major difference is seen in the earlier expression of the even-skipped gene in the developing spider heart compared with Drosophila, implying that the role of even-skipped in heart formation might have changed during arthropod evolution. The most striking finding, however, is that in addition to the dorsal tissue of the fourth walking leg segment and the opisthosomal segments, we discovered tinman-expressing cells that arise from a position dorsal to the cephalic lobe and that contribute to the anterior dorsal vessel. In contrast to the posterior heart tissue, these cells do not express the other heart genes. The spider heart thus is composed of two distinct populations of cells.
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| 4. |
- Janssen, Ralf, et al.
(författare)
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The T-box genes H15 and optomotor-blind in the spiders Cupiennius salei, Tegenaria atrica and Achaearanea tepidariorum and the dorsoventral axis of arthropod appendages
- 2008
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 10:2, s. 143-154
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Tidskriftsartikel (refereegranskat)abstract
- Dorsoventral axis formation in the legs of the fly Drosophila melanogaster requires the T-box genes optomotor-blind (omb) and H15. Evolutionary conservation of the patterning functions of these genes is unclear, because data on H15 expression in the spider Cupiennius salei did not support a general role of H15 in ventral fate specification. However, H15 has a paralogous gene, midline (mid) in Drosophila and H15 duplicates are also present in Cupiennius and the millipede Glomeris marginata. H15 therefore seems to have been subject to gene duplication opening the possibility that the previous account on Cupiennius has overlooked one or several paralogs. We have studied omb- and H15-related genes in two additional spider species, Tegenaria atrica and Achearanea tepidariorum and show that in both species one of the H15 genes belongs to a third group of spider H15 genes that has an expression pattern very similar to the H15 pattern in Drosophila. The expression patterns of all omb-related genes are also very similar to the omb expression pattern in Drosophila. These data suggest that the dorsoventral patterning functions of omb and H15 are conserved in the arthropods and that the previous conclusions were based on an incomplete data set in Cupiennius. Our results emphasize the importance of a broad taxon sampling in comparative studies.
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| 5. |
- Kodandaramaiah, Ullasa
(författare)
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Eyespot evolution : phylogenetic insights from Junonia and related butterfly genera (Nymphalidae)
- 2009
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 11:5, s. 489-497
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Tidskriftsartikel (refereegranskat)abstract
- Butterfly eyespots have been the focus of a number of developmental and evolutionary studies. However, a phylogenetic component has rarely been explicitly incorporated in these studies. In this study, I utilize a phylogeny to trace the evolution of eyespot number and position on the wing in a group of nymphalid butterflies, the subtribe Junoniini. These butterflies have two kinds of eyespot arrangements which I refer to as Serial and Individual. In the Serial arrangement, eyespots are placed in a series on compartments 1-6 (counting from the anterior wing margin). In the Individual arrangement, eyespots are isolated on specific compartments, ranging from 1 to 4 in number. This can be divided into four subtypes based on the number and positions of eyespots. I map the evolution of these five arrangements over a phylogeny of Junoniini reconstructed with ca. 3000 base pairs of sequence data from three genes. The results show that almost all arrangements have evolved at least twice, with multiple shifts between them by addition and deletion of eyespots. I propose a model involving genetic or developmental coupling between eyespots in specific compartments to explain these shifts. I discuss their evolution in light of existing knowledge about their development. I also discuss potential explanations for functional significance of the eyespot patterns found in the group. Differential selection for and against eyespots, both at different times over the phylogeny and in different regions, have driven the evolution of eyespot arrangements. The study throws open many questions about the adaptive significance of eyespots and the developmental underpinnings of the various arrangements.
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| 6. |
- Prpic, Nikola-Michael, et al.
(författare)
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Evolution of dorsal–ventral axis formation in arthropod appendages : H15 and optomotor-blind/bifid-type T-box genes in the millipede Glomeris marginata (Myriapoda: Diplopoda)
- 2005
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 7:1, s. 51-57
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Tidskriftsartikel (refereegranskat)abstract
- In Drosophila, the T-box genes optomotor-blind (omb) and H15 have been implicated in specifying the development of the dorso-ventral (DV) axis of the appendages. Results from the spider Cupiennius salei have suggested that this DV patterning system may be at least partially conserved. Here we extend the study of the DV patterning genes omb and H15 to a representative of the Myriapoda in order to add to the existing comparative data set and to gain further insight into the evolution of the DV patterning system in arthropod appendages. The omb gene of the millipede Glomeris marginata is expressed on the dorsal side of all appendages including trunk legs, maxillae, mandibles, and antennae. This is similar to what is known from Drosophila and Cupiennius and suggests that the role of omb in instructing dorsal fates is conserved in arthropods. Interestingly, the lobe-shaped portions of the mouthparts do not express omb, indicating that these are ventral components and thus may be homologous to the endites present in the corresponding appendages in insects. Concerning the H15 gene we were able to identify two paralogous genes in Glomeris. Both genes are expressed in the sensory organs of the maxilla and antenna, but only Gm-H15-1 is expressed along the ventral side of the trunk legs. The expression is more extensive than in Cupiennius, but less so than in Drosophila. In addition, no ventral expression domain is present in the maxilla, mandible, and antenna. Because of this, the role of H15 in the determination of ventral fate remains unclear.
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| 7. |
- Vázquez-Lobo, Alejandra, et al.
(författare)
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Characterization of the expression patterns of LEAFY/FLORICAULA and NEEDLY orthologs in female and male cones of the conifer genera Picea, Podocarpus, and Taxus : Implications for current evo-devo hypotheses for gymnosperms
- 2007
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 9:5, s. 446-459
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Tidskriftsartikel (refereegranskat)abstract
- The identity of genes causally implicated in the development and evolutionary origin of reproductive characters in gymnosperms is largely unknown. Working within the framework of plant evolutionary developmental biology, here we have cloned, sequenced, performed phylogenetic analyses upon and tested the expression patterns of LEAFY/FLORICAULA and NEEDLY orthologs in reproductive structures from selected species of the conifer genera Picea, Podocarpus, and Taxus. Contrary to expectations based on previous assessments, expression of LFY/FLO and NLY in cones of these taxa was found to occur simultaneously in a single reproductive axis, initially overlapping but later in mutually exclusive primordia and/or groups of developing cells in both female and male structures. These observations directly affect the status of the "mostly male theory" for the origin of the angiosperm flower. On the other hand, comparative spatiotemporal patterns of the expression of these genes suggest a complex genetic regulatory network of cone development, as well as a scheme of functional divergence for LFY/FLO with respect to NLY homologs in gymnosperms, both with clear heterochronic aspects. Results presented in this study contribute to the understanding of the molecular-genetic basis of morphological evolution in conifer cones, and may aid in establishing a foundation for gymnosperm-specific, testable evo-devo hypotheses.
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| 8. |
- Wennberg, Sofia, et al.
(författare)
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Early embryonic development of the priapulid worm Priapulus caudatus
- 2008
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 10:3, s. 326-338
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Tidskriftsartikel (refereegranskat)abstract
- The early cleavage up to gastrulation is described here for the priapulid worm Priapulus caudatus, contradicting and clarifying earlier partial reports on this topic. The cleavage pattern up to gastrulation is highly symmetrical, total, subequal, radial, and stereotypical. Gastrulation is intermediate between epiboly and invagination, and the mesendoderm may be derived from both cells of the first cleavage, thus differing significantly in its origin from that of many other protostomes. Priapulids occupy an increasingly important position in studies of animal evolution as they appear to be relatively basal within the new clade Ecdysozoa (panarthropods plus cycloneuralians); and have been described as both morphological and genetic living fossils. The insights derived from priapulids combined with new data published recently on kinorhynchs and tardigrades imply a substantial developmental diversity among basal ecdysozoans, and weakens the hypothesis that irregular cleavage is plesiomorphic to the entire clade. Further study is required to reconstruct basal cleavage patterns in both this clade, and indeed, the Bilateria as a whole.
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