Catálogo de publicaciones - revistas

<jats:title>Dinosaur Plumage</jats:title> <jats:p> Coloration and appearance provide important behavioral and evolutionary information in animals. However, for the most part, we do not know the coloration of fossil terrestrial animals. <jats:bold> Li <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1369" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1186290">1369</jats:related-article> , published online 4 February) have reconstructed the appearance of a theropod dinosaur by mapping features of its well-preserved feathers and comparing them with modern samples from birds. Feather color is partly determined by melanosome density and shape, and this information is preserved in a recently discovered fossil from China. The dinosaur was gray with white limbs and had a reddish crest and a speckled face. </jats:p>

<jats:title>Speak to Me, Mama</jats:title> <jats:p> Maternal effects are effects of the mother (for example, hormones) on her offspring that are independent of genetic inheritance, but related to the mother's phenotype and her environment. Despite their universal occurrence, little is known about the evolutionary influence of maternal effects. <jats:bold> Hinde <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1373" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1186056">1373</jats:related-article> ; see the cover) modeled maternal effects in birds and showed that nestling begging, as well as provoking feeding, also provides parents with information about offspring vigor. Conversely, maternal effects provide information to the unborn offspring about parental quality. Experimental studies with canaries provided support for the theoretical predictions, and together these studies show that parent-offspring conflict (that is, the conflict between the offspring for its immediate needs and the need of the parent to conserve resources for any future offspring) is resolved by the reciprocal exchange of information before and after birth. Hormonal signaling ensures a match between parental capacity for resource provisioning and offspring behavior and development after hatching that meet the mother's capacity to provide resources. </jats:p>

<jats:title>Theoretically Speedy Trees</jats:title> <jats:p> Phylogenetic tree construction often uses distance matrix methods, which offer promising scalable methods for rapid building of very large phylogenies. It has generally been assumed that trees constructed from distance matrices are intrinsically less accurate than those inferred from maximum likelihood methods, but the latter are slower to make. <jats:bold>Roch</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1376" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1182300">1376</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5971" page="1334" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1187797">Allman and Rhodes</jats:related-article> </jats:bold> ) theoretically examined this problem and showed that distance methods can achieve the same level of accuracy as likelihood methods. Thus, the generally assumed tradeoff between accuracy and speed in phylogenetic reconstruction can be overcome. </jats:p>

<jats:title>Moving Signals</jats:title> <jats:p> Many types of human breast cancers overexpress a cell-surface receptor—EphA2—a tyrosine kinase activated by the ligand ephrin-A1 present on adjoining cells. <jats:bold> Salaita <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1380" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1181729">1380</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5971" page="1335" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1187865"> <jats:bold>Paszek and Weaver</jats:bold> ) </jats:related-article> </jats:bold> studied the regulation of mechanically stimulated EphA2 signaling by inducing intermembrane signaling between living EphA2-expressing human breast cancer cells and supported membranes displaying laterally mobile ephrin-A1. When the receptors engaged their ligands, they formed clusters that moved radially to the junction between the cells and the membranes. Physically impeding this movement altered the cellular response to ephrin-A1. Different breast cancer cell lines showed differences in receptor movement that correlated with their invasion potential, and might indicate their capacity for metastasis formation. </jats:p>

<jats:title>Hair Today, Skin Tomorrow</jats:title> <jats:p> The epidermis of mammals contains hair follicles, sebaceous glands, and interfollicular epidermis, but it has not been clear how the development and repair of these structures is regulated. <jats:bold> Snippert <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1385" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1184733">1385</jats:related-article> ) show that a stem-cell cluster in the hair follicle, characterized by the expression of Lgr6, a close homolog of the Lgr5 marker for stem cells in the small intestine and colon, resides directly above the hair bulge and gives rise to all cell lineages of the skin. Skin wounds in adult mice are repaired by Lgr6 stem cells in the hair follicles that flank the damage. After hair morphogenesis, Lgr6 stem cells give rise to epidermal and sebaceous gland lineages to generate fully differentiated new skin. </jats:p>

<jats:title>Steady As She Blows</jats:title> <jats:p> A fundamental characteristic of many biological control networks is the capacity to maintain the concentration of a particular component at steady state within a narrow range, in spite of variations in the amounts of other network components that might change as a result of environmental variables in the state of a cell. In a mathematical analysis, <jats:bold>Shinar and Feinberg</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1389" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1183372">1389</jats:related-article> ) reveal the essential requirements of a network robust to perturbation. Using this method, the sources of robustness in two bacterial systems—one that functions in osmoregulation and another that controls carbon flux in metabolism—were explained. </jats:p>

<jats:title>Diheme Conversion</jats:title> <jats:p> A dehydrogenase enzyme found in methylotrophic and autotrophic bacteria, which converts methylamine to ammonia and formaldehyde, must be posttranslationally modified to create a covalently bound cofactor. Synthesis of the cofactor is completed by a diheme enzyme, MauG, which oxidatively links two tryptophan residues to form tryptophan tryptophylquinone. <jats:bold> Jensen <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1392" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1182492">1392</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5971" page="1337" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1187421">Bollinger and Matthews</jats:related-article> </jats:bold> ) describe the crystal structure of a catalytically competent complex of MauG bound to the methylamine dehydrogenase precursor. The reactive tryptophans are buried and well-separated from both heme irons. The heme closest to the nascent tryptophylquinone site is a 6-coordinate with an unusual His-Tyr axial link. The axial Tyr likely stabilizes a <jats:italic>bis</jats:italic> -Fe(IV) state involved in catalysis. Two other tyrosine residues are positioned to participate in long-range interprotein electron and radical transfer. </jats:p>

<jats:p>The show includes parent-offspring conflict in birds, peace through vaccine diplomacy, ocean versus land biodiversity, and more.</jats:p>

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