Catálogo de publicaciones - revistas

<jats:title>Quick-Dry Region</jats:title> <jats:p> The Sahara Desert is one of the driest places on Earth. However, 11,000 to 5000 years ago, it was a relatively lush region containing savannah grasslands and humid tropical forests. This interval, the Early Holocene African Humid Period, ended, of course, but whether the drying occurred rapidly or gradually is unclear. <jats:bold>Tierney and deMenocal</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="843" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1240411">843</jats:related-article> , published online 10 October; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="808" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1246519">Bard</jats:related-article> </jats:bold> ) report results from the Horn of Africa that suggest that the transitions both into and out of the humid period were abrupt—occurring within centuries rather than over millennia. </jats:p>

<jats:title>Getting the Dosage Right</jats:title> <jats:p> As sex chromosomes evolve, they must compensate for differential gene dosage, especially in non-sex-specific genes. However, owing to the relative rarity of chromosomes that are in the process of becoming sex chromosomes, the ongoing evolutionary processes resulting in dosage compensation are unclear. <jats:bold>Ellison and Bachtrog</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="846" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1239552">846</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="6160" page="812" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1246659">Chuong and Feschotte</jats:related-article> </jats:bold> ) identified a specific transposable element involved in dosage compensation in males on the evolutionarily new neo-X chromosome of <jats:italic>Drosophila miranda</jats:italic> . A particular copy of this transposable element has been inserted at chromatin entry sites on the neo-X chromosome that favorably binds to the male-specific lethal complex, which in turn facilitates the spreading of chromatin silencing on a single chromosome to provide dosage compensation. </jats:p>

<jats:title>Forests in Flux</jats:title> <jats:p> Forests worldwide are in a state of flux, with accelerating losses in some regions and gains in others. <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" issue="6160" page="850" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1244693">850</jats:related-article> ) examined global Landsat data at a 30-meter spatial resolution to characterize forest extent, loss, and gain from 2000 to 2012. Globally, 2.3 million square kilometers of forest were lost during the 12-year study period and 0.8 million square kilometers of new forest were gained. The tropics exhibited both the greatest losses and the greatest gains (through regrowth and plantation), with losses outstripping gains. </jats:p>

<jats:title>Scaling Spindle Size</jats:title> <jats:p> The difficulty of modulating cell size in vivo has made it hard to test hypotheses for organelle size scaling during development. To this end, <jats:bold> Hazel <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="853" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243110">853</jats:related-article> ) and <jats:bold> Good <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="856" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243147">856</jats:related-article> ) developed microfluidic systems in which cytoplasmic extracts are encapsulated in compartments with definable size. The size of mitotic spindles assembled within cell-free extracts scaled with the volume of the compartment within which the spindle assembled. The findings suggest that the diminished availability of cytoplasmic components, notably tubulin, concomitant with cell size reduction, prescribes a smaller spindle size. </jats:p>

<jats:title>Scaling Spindle Size</jats:title> <jats:p> The difficulty of modulating cell size in vivo has made it hard to test hypotheses for organelle size scaling during development. To this end, <jats:bold> Hazel <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="853" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243110">853</jats:related-article> ) and <jats:bold> Good <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="856" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243147">856</jats:related-article> ) developed microfluidic systems in which cytoplasmic extracts are encapsulated in compartments with definable size. The size of mitotic spindles assembled within cell-free extracts scaled with the volume of the compartment within which the spindle assembled. The findings suggest that the diminished availability of cytoplasmic components, notably tubulin, concomitant with cell size reduction, prescribes a smaller spindle size. </jats:p>

<jats:title>The Root of the Problem</jats:title> <jats:p> The quiescent center (QC) within the root meristem plays a key role as a stem cell organizer to sustain the root stem cell niche. The QC cells execute a dual role: prevention of the differentiation of neighboring stem cells, and maintenance of the root structure by undergoing only occasional cell division. The mechanisms that account for the low QC proliferation are unclear, although the anaphase-promoting complex/cyclosome (APC/C) E3 ubiquitin ligase is known to suppress QC cell division. Through a systematic functional analysis of APC/C-copurifying proteins, <jats:bold> Heyman <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="860" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1240667">860</jats:related-article> ) characterized a transcription factor ERF115 as a rate-limiting factor for QC cell division. ERF115 needs to be destroyed to retain QC cells in a resting state. ERF115 operates in a brassinosteroid-dependent manner and controls QC cell division through transcriptional activation of phytosulfokine signaling. </jats:p>

<jats:title>Slipping the NET</jats:title> <jats:p> One spectacular response to bacterial infection is the release of NETs (neutrophil extracellular traps) of DNA from polymorphonuclear leukocytes that immobilize the pathogens and prevent phagocytosis by macrophages. <jats:italic>Staphylococcus aureus</jats:italic> evades NETs by degrading the DNA into deoxyadenosine (dAdo). <jats:bold> Thammavongsa <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="863" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1242255">863</jats:related-article> ) found that dAdo also promotes immune cell death, which appears to ensure the exclusion of macrophages from the center of abscesses within which the bacteria survive. </jats:p>

<jats:title>Answers from Exomes</jats:title> <jats:p> Exome sequencing, which targets only the protein-coding regions of the genome, has the potential to identify the underlying genetic causes of rare inherited diseases. <jats:bold> Angulo <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="866" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243292">866</jats:related-article> , published online 17 October; see Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="814" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1246760">Conley and Fruman</jats:related-article> </jats:bold> ) performed exome sequencing of individuals from seven unrelated families with severe, recurrent respiratory infections. The patients carried the same mutation in the gene coding for the catalytic subunit of phosphoinositide 3-kinase δ (PI3Kδ). The mutation caused aberrant activation of this kinase, which plays a key role in immune cell signaling. Drugs inhibiting PI3Kδ are already in clinical trials for other disorders. </jats:p>

<jats:title>Dog Domestication</jats:title> <jats:p> The precise details of the domestication and origins of domestic dogs are unclear. <jats:bold> Thalmann <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="871" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243650">871</jats:related-article> ; see the cover) analyzed complete mitochondrial genomes from present-day dogs and wolves, as well as 18 fossil canids dating from 1000 to 36,000 years ago from the Old and New Worlds. The data suggest that an ancient, now extinct, central European population of wolves was directly ancestral to domestic dogs. Furthermore, several ancient dogs may represent failed domestication events. </jats:p>

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