| 1. |
- Carlsbecker, A, et al.
(författare)
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The DAL10 gene from Norway spruce (Picea abies) belongs to a potentially gymnosperm-specific subclass of MADS-box genes and is specifically active in seed cones and pollen cones.
- 2003
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Ingår i: Evolution & Development. - 1525-142X. ; 5:6, s. 551-561
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Tidskriftsartikel (refereegranskat)abstract
- Transcription factors encoded by different members of the MADS-box gene family have evolved central roles in the regulation of reproductive organ development in the flowering plants, the angiosperms. Development of the stamens and carpels, the pollen- and seed-bearing organs, involves the B- and C-organ-identity MADS-box genes. B- and C-type gene orthologs with activities specifically in developing pollen- and seed-bearing organs are also present in the distantly related gymnosperms: the conifers and the gneto-phytes. We now report on the characterization of DAL10, a novel MADS-box gene from the conifer Norway spruce, which unlike the B- and C-type conifer genes shows no distinct orthology relationship to any angiosperm gene or clade in phylogenetic analyses. Like the B- and C-type genes, it is active specifically in developing pollen cones and seed cones. In situ RNA localization experiments show DAL10 to be expressed in the cone axis, which carry the microsporophylls of the young pollen cone. In contrast, in the seed cone it is expressed both in the cone axis and in the bracts, which subtend the ovuliferous scales. Expression data and the phenotype of transgenic Arabidopsis plants expressing DAL10 suggest that the gene may act upstream to or in concert with the B- and C-type genes in the establishment of reproductive identity of developing cones.
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| 2. |
- 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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| 3. |
- 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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| 4. |
- Englund, Marie, et al.
(författare)
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Morphological "primary homology" and expression of AG -subfamily MADS-box genes in pines, podocarps, and yews
- 2011
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 13:2, s. 171-181
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Tidskriftsartikel (refereegranskat)abstract
- The morphological variation among reproductive organs of extant gymnosperms is remarkable, especially among conifers. Several hypotheses concerning morphological homology between various conifer reproductive organs have been put forward, in particular in relation to the pine ovuliferous scale. Here, we use the expression patterns of orthologs of the ABC-model MADS-box gene AGAMOUS (AG) for testing morphological homology hypotheses related to organs of the conifer female cone. To this end, we first developed a tailored 3'RACE procedure that allows reliable amplification of partial sequences highly similar to gymnosperm-derived members of the AG-subfamily of MADS-box genes. Expression patterns of two novel conifer AG orthologs cloned with this procedure-namely PodAG and TgAG, obtained from the podocarp Podocarpus reichei and the yew Taxus globosa, respectively-are then further characterized in the morphologically divergent female cones of these species. The expression patterns of PodAG and TgAG are compared with those of DAL2, a previously discovered Picea abies (Pinaceae) AG ortholog. By treating the expression patterns of DAL2, PodAG, and TgAG as character states mapped onto currently accepted cladogram topologies, we suggest that the epimatium-that is, the podocarp female cone organ previously postulated as a "modified" ovuliferous scale-and the canonical Pinaceae ovuliferous scale can be legitimally conceptualized as "primary homologs." Character state mapping for TgAG suggests in turn that the aril of Taxaceae should be considered as a different type of organ. This work demonstrates how the interaction between developmental-genetic data and formal cladistic theory could fruitfully contribute to gymnosperm systematics.
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| 5. |
- Frygelius, Jessica, et al.
(författare)
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Evolution and human tissue expression of the Cres/Testatin subgroup genes, a reproductive tissue specific subgroup of the type 2 cystatins
- 2010
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 12:3, s. 329-342
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Tidskriftsartikel (refereegranskat)abstract
- P>The cystatin family comprises a group of generally broadly expressed protease inhibitors. The Cres/Testatin subgroup (CTES) genes within the type 2 cystatins differs from the classical type 2 cystatins in having a strikingly reproductive tissue-specific expression, and putative functions in reproduction have therefore been discussed. We have performed evolutionary studies of the CTES genes based on gene searches in genomes from 11 species. Ancestors of the cystatin family can be traced back to plants. We have localized the evolutionary origin of the CTES genes to the split of marsupial and placental mammals. A model for the evolution of these genes illustrates that they constitute a dynamic group of genes, which has undergone several gene expansions and we find indications of a high degree of positive selection, in striking contrast to what is seen for the classical cystatin C. We show with phylogenetic relations that the CTES genes are clustered into three original groups, a testatin, a Cres, and a CstL1 group. We have further characterized the expression patterns of all human members of the subfamily. Of a total of nine identified human genes, four express putative functional transcripts with a predominant expression in the male reproductive system. Our results are compatible with a function of this gene family in reproduction.
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| 6. |
- Groth, Erika, 1980-, et al.
(författare)
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AGAMOUS subfamily MADS-box genes and the evolution of seed cone morphology in Cupressaceae and Taxodiaceae
- 2011
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 13:2, s. 159-170
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Tidskriftsartikel (refereegranskat)abstract
- In this comparative developmental genetics study, we test hypotheses based on fossil and morphological data on reproductive organ morphology and evolution in conifers-specifically, the ovule-bearing organ in Cupressaceae and Taxodiaceae. Genes homologous to the Arabidopsis gene AGAMOUS are expressed in ovuliferous scales of spruces (Picea) throughout development. Previous studies have shown that the AGAMOUS subfamily of MADS-box genes predates the split between angiosperms and gymnosperms, and that these genes have in part conserved functions in reproductive development among seed plants, especially in the specification of identity of the ovule-bearing organs. These data indicate that their expression in conifer families other than Pinaceae might be used as markers for organs homologous to the Pinaceae ovuliferous scale. Here we have isolated putative AGAMOUS orthologs from Cupressaceae and Taxodiaceae and analyzed their expression pattern in seed cones to test for the presence of morphological homologs of ovuliferous scales. Our results were not congruent with the hypothesis that the tooth of the Cryptomeria seed cone is homologous to the Picea ovuliferous scale. Likewise, the hypothesis that the bracts of Thujopsis and Juniperus contain fused ovuliferous scales was not supported. However, we found expression of AGAMOUS homologs in the sterile bracts of Cupressaceae seed cones at late developmental stages. This expression probably represents a novel gene function in these conifer families, since no corresponding expression has been identified in Pinaceae. Our study suggests that the evolutionary history of modern conifer cones is more diverse than previously thought.
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| 7. |
- Janssen, Ralf
(författare)
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Diplosegmentation in the pill millipede Glomeris marginata is the result of dorsal fusion
- 2011
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 13:5, s. 477-487
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Tidskriftsartikel (refereegranskat)abstract
- All trunk segments in the pill millipede Glomens marginata (Myriapoda: Diplopoda) are initially patterned genetically, (as visualized by the embryonic expression pattern of the even-skipped gene) and formed morphologically, (as visualized by 4-6-diamidin-2-phenylindol stained embryos) in a single segmental period. In addition, formation of every nascent trunk segment concerns ventral as well as dorsal segmental units. Only after the formation of the nascent posterior trunk segments, the dorsal segmental units of two adjacent segments fuse to form a single dorsal segmental unit that subsequently covers two ventral leg-bearing segmental units. The formation of a diplosegmental unit, or in short a diplosegment, is thus the result of dorsal fusion of embryonic tissue and not the result of any splitting-process or fusion of dorsal tergites. The new data also argue against heterochrony as a primary causative factor for the formation of the diplosegments during the formation of dorsal versus ventral segmental units. Furthermore, no evidence was found supporting the hypothesis that anterior trunk segments in diplopods represent degenerate diplosegments. Two possible scenarios arise from the ontogenetic data presented here, whether this represents an ancestral feature of the diplopods, or alternatively if they represent an isolated case only found in Glomeris (and close relatives). If the former is the case, my work may provide an impressive example of Haeckel's recapitulation theory.
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| 8. |
- 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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| 9. |
- Janssen, Ralf, 1975-, et al.
(författare)
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Gene expression patterns in an onychophoran reveal that regionalization predates limb segmentation in pan-arthropods
- 2010
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Ingår i: Evolution & Development. - 1520-541X .- 1525-142X. ; 12:4, s. 363-372
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Tidskriftsartikel (refereegranskat)abstract
- In arthropods, such as Drosophila melanogaster, the leg gap genes homothorax (hth), extradenticle (exd), dachshund (dac), and Distal-less (Dll) regionalize the legs in order to facilitate the subsequent segmentation of the legs. We have isolated homologs of all four leg gap genes from the onychophoran Euperipatoides kanangrensis and have studied their expression. We show that leg regionalization takes place in the legs of onychophorans even though they represent simple and nonsegmented appendages. This implies that leg regionalization evolved for a different function and was only later co-opted for a role in leg segmentation. We also show that the leg gap gene patterns in onychophorans (especially of hth and exd) are similar to the patterns in crustaceans and insects, suggesting that this is the plesiomorphic state in arthropods. The reversed hth and exd patterns in chelicerates and myriapods are therefore an apomorphy for this group, the Myriochelata, lending support to the Myriochelata and Tetraconata clades in arthropod phylogeny.
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| 10. |
- 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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