1,720,976 research outputs found
15-P027 Role of Hox genes in walking leg morphology specification in insects and spiders
No full textPatterning mechanisms and morphological diversity of spider appendages and their importance for spider evolution
No full textThe prosoma of spiders bears different gnathal (labrum, chelicerae, pedipalps) and locomotory appendages (legs). In most species these appendages are also used for additional functions, e.g. sensing, mating, and courtship. The opisthosoma is equipped with four pairs of highly specialized appendages. Two pairs of spinnerets are used for silk production and manipulation. The other two pairs of appendages are internalized during development and give rise to a complex respiratory system of book lungs and tracheae. Thus spiders have a number of different appendage types with radically different adult morphologies. Furthermore, all these appendage types display significant additional species specific diversity correlating with a large spectrum of functions of the appendages. Despite this importance of appendage diversity for the evolution of the spiders we know relatively little about the genetic patterning mechanisms producing this diversity of morphology. We review recent advances concerning the developmental genetics of spider appendage diversification, mainly concentrating on open questions and future directions of research. We conclude that the deeper understanding of appendage development and diversity in spiders can contribute significantly not only to evolutionary developmental biology, but also to behavioral biology, speciation research and population genetics, and the study of sexually dimorphic traits. (C) 2010 Elsevier Ltd. All rights reserved
Rapid diversification of homothorax expression patterns after gene duplication in spiders
No full textAbstract Background Gene duplications provide genetic material for the evolution of new morphological and physiological features. One copy can preserve the original gene functions while the second copy may evolve new functions (neofunctionalisation). Gene duplications may thus provide new genes involved in evolutionary novelties. Results We have studied the duplicated homeobox gene homothorax (hth) in the spider species Parasteatoda tepidariorum and Pholcus phalangioides and have compared these data with previously published data from additional spider species. We show that the expression pattern of hth1 is highly conserved among spiders, consistent with the notion that this gene copy preserves the original hth functions. By contrast, hth2 has a markedly different expression profile especially in the prosomal appendages. The pattern in the pedipalps and legs consists of several segmental rings, suggesting a possible role of hth2 in limb joint development. Intriguingly, however, the hth2 pattern is much less conserved between the species than hth1 and shows a species specific pattern in each species investigated so far. Conclusions We hypothesise that the hth2 gene has gained a new patterning function after gene duplication, but has then undergone a second phase of diversification of its new role in the spider clade. The evolution of hth2 may thus provide an interesting example for a duplicated gene that has not only contributed to genetic diversity through neofunctionalisation, but beyond that has been able to escape evolutionary conservation after neofunctionalisation thus forming the basis for further genetic diversification
Divergent role of the Hox gene Antennapedia in spiders is responsible for the convergent evolution of abdominal limb repression
No full textEvolution often results in morphologically similar solutions in different organisms, a phenomenon known as convergence. However, there is little knowledge of the processes that lead to convergence at the genetic level. The genes of the Hox cluster control morphology in animals. They may also be central to the convergence of morphological traits, but whether morphological similarities also require similar changes in Hox gene function is disputed. In arthropods, body subdivision into a region with locomotory appendages ("thorax") and a region with reduced appendages ("abdomen") has evolved convergently in several groups, e. g., spiders and insects. In insects, legs develop in the expression domain of the Hox gene Antennapedia (Antp), whereas the Hox genes Ultrabithorax (Ubx) and abdominal-A mediate leg repression in the abdomen. Here, we show that, unlike Antp in insects, the Antp gene in the spider Achaearanea tepidariorum represses legs in the first segment of the abdomen (opisthosoma), and that Antp and Ubx are redundant in the following segment. The down-regulation of Antp in A. tepidariorum leads to a striking 10-legged phenotype. We present evidence from ectopic expression of the spider Antp gene in Drosophila embryos and imaginal tissue that this unique function of Antp is not due to changes in the Antp protein, but likely due to divergent evolution of cofactors, Hox collaborators or target genes in spiders and flies. Our results illustrate an interesting example of convergent evolution of abdominal leg repression in arthropods by altering the role of distinct Hox genes at different levels of their action
Does leaky ryanodine receptors play any role in maladaptive remodeling after chronic mechanical stress in mice?
No full textProteomic analysis of short-term preload-induced eccentric cardiac hypertrophy
Full text linkBackground: Hemodynamic load leads to cardiac hypertrophy and heart failure. While afterload (pressure overload) induces concentric hypertrophy, elevation of preload (volume overload) yields eccentric hypertrophy and is associated with a better outcome. Here we analysed the proteomic pattern of mice subjected to short-term preload. Methods and Results: Female FVB/N mice were subjected to aortocaval shunt-induced volume overload that leads to an eccentric hypertrophy (left ventricular weight/tibia length +31 %) with sustained systolic heart function at 1 week after operation. Two-dimensional gel electrophoresis (2-DE) followed by mass spectrometric analysis showed alteration in the expression of 25 protein spots representing 21 different proteins. 64 % of these protein spots were up-regulated and 36 % of the protein spots were consistently down-regulated. Interestingly, alpha-1-antitrypsin was down-regulated, indicating higher elastin degradation and possibly contributing to the early dilatation. In addition to contractile and mitochondrial proteins, polymerase I and transcript release factor protein (PTRF) was also up-regulated, possibly contributing to the preload-induced signal transduction. Conclusions: Our findings reveal the proteomic changes of early-stage eccentric myocardial remodeling after volume overload. Induced expression of some of the respiratory chain enzymes suggests a metabolic shift towards an oxidative phosphorylation that might contribute to the favorable remodeling seen in early VO. Down-regulation of alpha-1-antitrypsin might contribute to extracellular matrix remodeling and left ventricular dilatation. We also identified PTRF as a potential signaling regulator of volume overload-induced cardiac hypertrophy
Does leaky ryanodine receptors play any role in maladaptive remodeling after chronic mechanical stress in mice?
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