Catálogo de publicaciones - revistas

<jats:title>Tailor-Made Tumor</jats:title> <jats:p> The biotrophic smut pathogen <jats:italic>Ustilago maydis</jats:italic> specifically infects the important crop plant, maize. The pathogen elicits large tumors on all aerial maize organs by redirecting primordia into a tumor pathway, and maize developmental mutants can disrupt tumor progression. <jats:bold> Skibbe <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="89" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1185775">89</jats:related-article> ) examined gene expression in parallel in both the host plant and the smut pathogen and found that organ-specific gene expression patterns were required in both for tumor formation. Thus, fungal pathogens may exert distinct effects on different organs and tissues in plants, perhaps explaining the diverse pathologies that can be produced in diseased plants. </jats:p>

<jats:title>The Size of the Father</jats:title> <jats:p> Evolutionary biologists have recently discovered an intriguing phenomenon: High-fitness males often sire low-fitness daughters. The emerging consensus is that this sexual conflict overwhelms the benefits of mate choice for “good genes,” thus challenging a central tenet of evolutionary theory. <jats:bold>Cox and Calsbeek</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="92" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1185550">92</jats:related-article> , published online 4 March) provide a counterpoint by showing that female brown anole lizards can obtain genetic benefits by biasing offspring sex to produce disproportionately more sons with high-fitness (large) sires. The advantage of this sex-ratio bias was confirmed by tracking the fitness of sons and daughters in their natural environment, illustrating the importance of sexual conflict in the wild. Thus, because maximal fitness payoffs can be achieved by shifting offspring production from daughters to sons as sire size increases, mate choice can overcome antagonistic fitness effects. </jats:p>

<jats:title>Histone Inheritance</jats:title> <jats:p> Chromatin, the packaging material for eukaryotic genomes, is a potential repository for epigenetic information. The core structure of chromatin is the nucleosome, which consists of an octamer of histone proteins, two dimers each of histones H2A and H2B, and histones 3 and 4. Histones 3 and 4, in particular, carry a series of covalent modifications presumed to be passed on through cell division. Using mass spectrometry of tagged and isotope labeled histones, <jats:bold> Xu <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="94" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1178994">94</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5974" page="56" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1188653"> <jats:bold>Ray-Gallet and Almouzni</jats:bold> </jats:related-article> <jats:bold /> ) followed the inheritance of the histones themselves through mitosis. The H2A-H2B dimers were inherited randomly through cell division, correlating with their lack of major covalent marks. In comparison, replication-deposited H3.1-H4 dimers did not separate through cell division, implying that H3 and H4 histone modifications might be maintained by copying from neighboring preexisting histones. Intriguingly, up to one-quarter of the nonreplication-deposited H3.3-H4 dimers, which mark active chromatin, did split during cell division. </jats:p>

<jats:title>Open Sesame</jats:title> <jats:p> The proteosome plays a key role in cellular homeostasis through catalyzing protein degradation. It is a barrel-shaped nanomachine whose activity is regulated through gating substrate entry. <jats:bold> Religa <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="98" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1184991">98</jats:related-article> ) now show that N-terminal gating residues in the proteasome interconvert on a second's time-scale between conformations that place them either outside or inside the proteasomal antechamber. An increase in the number of termini occupying the “in” state decreased rates of hydrolysis. Furthermore, proteasome activators known to increase the proteolysis rate lead to an increase in the number of termini in the “out” state. </jats:p>

<jats:title>Cytomegalovirus Immune Evasion Strategy</jats:title> <jats:p> Cytomegalovirus (CMV) infects a large percentage of the world's population. Most of those infected are asymptomatic; however, CMV is a substantial public health concern for immunocompromised individuals and neonates. CMV is unusual in that it can superinfect: it re-infects hosts who are already infected with the virus, even in the presence of a strong, specific immune response. <jats:bold> Hansen <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="102" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1185350">102</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="5974" page="51" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1188578"> <jats:bold>Hengel and Koszinowski</jats:bold> </jats:related-article> </jats:bold> ) now find that in rhesus macaques, a good model for human CMV superinfection, CMV establishes superinfections by evading the immune response mediated by CD8 <jats:sup>+</jats:sup> T cells. A series of viral mutants deficient in expression of the US2-11 glycoproteins, which regulate antigen presentation to CD8 <jats:sup>+</jats:sup> T cells, revealed that, although able to establish the initial infection, these viral mutants were unable to superinfect. Depletion of CD8 <jats:sup>+</jats:sup> T cells from the monkeys allowed infection by the mutant viruses. These results highlight the difficulties in developing an effective protective vaccine against CMV itself, but suggest that CMV-based vectors may be useful in other vaccine efforts such as those against HIV. </jats:p>

<jats:title>Precise and Efficient Cortical Communication</jats:title> <jats:p> How do thalamic neurons reliably transmit information to the cerebral cortex, despite making few synaptic connections onto their target neurons? Correlated input spikes from the thalamus have been reported, but the number of synchronous inputs and their precision and reliability is unclear. <jats:bold> Wang <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="106" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1183108">106</jats:related-article> ) analyzed a unique data set of simultaneous thalamic and cortical recordings in vivo and compared them with simulations of a model cortical neuron. Using the recorded spike trains as inputs to the model, and constraining the model by the measured output spike trains, allowed strong predictions of the degree of convergence of synchronous inputs from the lateral geniculate nucleus. Synchrony, rather than the strength or frequency of synaptic inputs, was key to signaling, and the data suggest that there may be a region of optimal synchronous coding. </jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>

<jats:p>The show includes insights from chimpanzee research, how cytomegalovirus evades the immune system, sinking sea floors, and more.</jats:p>