Catálogo de publicaciones - revistas

<jats:title>How plant species diversity is shaped</jats:title> <jats:p> Factors controlling plant species diversity have been teased apart in an ancient dune ecosystem in western Australia. Laliberté <jats:italic>et al.</jats:italic> surveyed plants in the ancient dune, where variation in soil properties is associated with changes in plant diversity. Local plant diversity was mostly determined by environmental filtering from the regional species pool. This process is driven by acidification during long-term soil formation. The findings challenge the prevailing view that resource competition controls local plant diversity. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6204" page="1602" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1256330">1602</jats:related-article> </jats:p>

<jats:title>A complex network makes simple pores</jats:title> <jats:p> Stomata, the pores found on the surface of plant leaves, form at intervals from stem cells. Development of stomata is controlled by the SPEECHLESS transcription factor. Lau <jats:italic>et al.</jats:italic> surveyed the genes that SPEECHLESS itself controls. Targets include genes involved in hormone signaling, control of cell proliferation, and the specification of asymmetric cell fates. Despite the apparent simplicity of a single pore, the genetic network that generates that pore is anything but simple. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6204" page="1605" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1256888">1605</jats:related-article> </jats:p>

<jats:title>An early assemblage of obsidian artifacts</jats:title> <jats:p> Levallois technology is the name for the stone knapping technique used to create tools thousands of years ago. The technique appeared in the archeological record across Eurasia 200 to 300 thousand years ago (ka) and appeared earlier in Africa. Adler <jats:italic>et al.</jats:italic> challenge the hypothesis that the technique's appearance in Eurasia was the result of the expansion of hominins from Africa. Levallois obsidian artifacts in the southern Caucasus, dated at 335 to 325 ka, are the oldest in Eurasia. This suggests that Levallois technology may have evolved independently in different hominin populations. Stone technology cannot thus be used as a reliable indicator of Paleolithic human population change and expansion. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6204" page="1609" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1256484">1609</jats:related-article> </jats:p>

<jats:title>Mysterious dinosaur a swimmer?</jats:title> <jats:p> Dinosaurs are often appreciated for their size and oddity. In this regard, the North African carnivorous theropod <jats:italic>Spinosaurus</jats:italic> , with its huge dorsal sail and a body larger than <jats:italic>Tyrannosaurus rex</jats:italic> , has long stood out. This species also stands out because of its history. The unfortunate loss of the type specimen during World War II left much of what we know about <jats:italic>Spinosaurus</jats:italic> to be divined through speculation and reconstruction. Ibrahim <jats:italic>et al.</jats:italic> now describe new fossils of this unusual species. They conclude it was, at least partly, aquatic, a first for dinosaurs. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6204" page="1613" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1258750">1613</jats:related-article> </jats:p>

<jats:title>Animal behavior follows rewards</jats:title> <jats:p> Animal behavior is learned and reinforced by rewards. On a molecular level, the reward comes in the form of the neurotransmitter, dopamine, which modulates synapses. The exact timing and mechanism of this process remain unknown. Using optical stimulation, Yagishita <jats:italic>et al.</jats:italic> found that dopaminergic modulation involved dendritic spine enlargement only during an extremely narrow time window. Known as reinforcement plasticity, this cellular basis for learning could provide insight into psychiatric disorders involving dopaminergic regulation, such as depression, drug addiction, and schizophrenia. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6204" page="1616" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1255514">1616</jats:related-article> </jats:p>

<jats:title>Making nitrogen available for biosynthesis</jats:title> <jats:p> Nitrogen gas (N <jats:sub>2</jats:sub> ) is abundant in Earth's atmosphere; however, it must be converted into a bioavailable form before it can be incorporated into biomolecules. The enzyme nitrogenase, which is made up of two metalloproteins, converts N <jats:sub>2</jats:sub> into bioavailable ammonia. One of these, the MoFe-protein, contains a complex metal center, the FeMo cofactor, where the triple N <jats:sub>2</jats:sub> bond is reduced. Understanding how nitrogenase achieves the reduction of N <jats:sub>2</jats:sub> has been a long-term goal. Spatzal <jats:italic>et al.</jats:italic> present the structure of MoFe-protein bound to carbon monoxide (see the Perspective by Hogbom). Although this is an inhibitor rather than the natural substrate, the structure gives insight into how the FeMo metallocluster rearranges to achieve substrate reduction. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6204" page="1620" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1256679">1620</jats:related-article> </jats:p>

<jats:title>Beware of T cells that don't know how to stop</jats:title> <jats:p> During an infection, T cells divide extensively and secrete proteins that can severely damage tissues. But T cells know when to stop—they express proteins on their surface such as CTLA4, which put on the brakes. Kuehn <jats:italic>et al.</jats:italic> now report genetic evidence of the importance of CTLA4 in humans (see the Perspective by Rieux-Laucat and Casanova). They identified six patients with mutations in one copy of <jats:italic>CTLA4</jats:italic> . Patients presented with symptoms of an overzealous immune response, with immune cells infiltrating their organs. The findings support the idea that CTLA4 tells the immune system when enough is enough. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6204" page="1623" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1255904">1623</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6204" page="1560" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1260791">1560</jats:related-article> </jats:p>

<jats:p> This issue of <jats:italic>Science</jats:italic> includes the program of the 2015 AAAS Annual Meeting. </jats:p> <jats:p>2015 “Session I” Meetings will be held between January and May in California and Texas in the United States, and internationally in Lucca (Barga), Italy and Hong Kong, China.</jats:p> <jats:p> A <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.sciencemag.org/cgi/reprint/345/6204/1628.pdf">PDF</jats:ext-link> of the program as it appears in this issue is available here; for more information on the meeting (including registration forms and information on accommodations), please visit <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="www.grc.org">www.grc.org</jats:ext-link> . </jats:p>

<jats:p>On this week's show: Tracing the roots of an ancient stone-age technology and a daily news round up with David Grimm.</jats:p>

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