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<jats:title>Limiting unknows in the dark side</jats:title> <jats:p> Our knowledge of the inventory of stuff that makes up our universe amounts to a humbling 5%. The rest consists of either dark energy (~70%) or dark matter (~25%). Using atom interferometry, Hamilton <jats:italic>et al.</jats:italic> describe the results of experiments that controlled for dark energy screening mechanisms in individual atoms, not bulk matter. Aprile <jats:italic>et al.</jats:italic> report on an analysis of data taken with the XENON100 detectors aiming to identify dark matter particles directly by monitoring their rare interaction with ordinary matter. In this setup, a large underground tank of liquid xenon forms a target for weakly interacting m assive particles. These combined results set limits on several types of proposed dark matter and dark energy candidates (see the Perspective by Schmiedmayer and Abele). </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="6250" page="849" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa8883">849</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6250" page="851" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab2069">851</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6250" page="786" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac9828">786</jats:related-article> </jats:p>

<jats:title>Limiting unknows in the dark side</jats:title> <jats:p> Our knowledge of the inventory of stuff that makes up our universe amounts to a humbling 5%. The rest consists of either dark energy (~70%) or dark matter (~25%). Using atom interferometry, Hamilton <jats:italic>et al.</jats:italic> describe the results of experiments that controlled for dark energy screening mechanisms in individual atoms, not bulk matter. Aprile <jats:italic>et al.</jats:italic> report on an analysis of data taken with the XENON100 detectors aiming to identify dark matter particles directly by monitoring their rare interaction with ordinary matter. In this setup, a large underground tank of liquid xenon forms a target for weakly interacting m assive particles. These combined results set limits on several types of proposed dark matter and dark energy candidates (see the Perspective by Schmiedmayer and Abele). </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="6250" page="849" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa8883">849</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6250" page="851" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab2069">851</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6250" page="786" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac9828">786</jats:related-article> </jats:p>

<jats:title>A model for who eats and who is eaten</jats:title> <jats:p> There are many types of interactions between those that eat and those that are eaten. A multitude of theoretical equations describe these dynamics, from predator and prey to parasite and host. Lafferty <jats:italic>et al.</jats:italic> show that all forms of these relationships come down to fundamental consumer-resource interactions. Derived from the myriad complex interactions, a simple model can accommodate any such interaction, simplifying past models into a general theory of eat and be eaten. </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="6250" page="854" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa6224">854</jats:related-article> </jats:p>

<jats:title>An anomalous and unbalanced predator</jats:title> <jats:p> In the past century, humans have become the dominant predator across many systems. The species that we target are thus far in considerable decline; however, predators in the wild generally achieve a balance with their prey populations such that both persist. Darimont <jats:italic>et al.</jats:italic> found several specific differences between how humans and other predatory species target prey populations (see the Perspective by Worm). In marine environments, for example, we regularly prey on other predator species. These differences may contribute to our much larger ecological impact when compared with other predators. </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="6250" page="858" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac4249">858</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6250" page="784" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac8697">784</jats:related-article> </jats:p>

<jats:title>Immune signals shape root communities</jats:title> <jats:p> To thwart microbial pathogens aboveground, the plant <jats:italic>Arabidopsis</jats:italic> turns on defensive signaling using salicylic acid. In <jats:italic>Arabidopsis</jats:italic> plants with modified immune systems, Lebeis <jats:italic>et al.</jats:italic> show that bacterial communities change in response to salicylic acid signaling in the root zone as well (see the Perspective by Haney and Ausubel). Abundance of some root-colonizing bacterial families increased at the expense of others, partly as a function of whether salicylic acid was used as an immune signal or as a carbon source for microbial growth. </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="6250" page="860" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa8764">860</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6250" page="788" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aad0092">788</jats:related-article> </jats:p>

<jats:title>Germination signals illuminated</jats:title> <jats:p> The noxious weed <jats:italic>Striga</jats:italic> can take down an entire crop. Fields in Africa are particularly susceptible to the devastation it can cause. <jats:italic>Striga</jats:italic> seeds germinate in response to faint traces of the hormone strigolactone released by its targets. Tsuchiya <jats:italic>et al.</jats:italic> designed a mimic of strigolactone that, when cleaved by the Striga receptor, generates a fluorescent end product. This photogenic mimic lit up <jats:italic>Striga</jats:italic> seeds upon germination and led to the identification of its strigolactone receptor. Abolishing the activity of this receptor could be an effective defensive strategy. </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="6250" page="864" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab3831">864</jats:related-article> </jats:p>

<jats:title>Regulation of splicing regulators</jats:title> <jats:p> The messenger RNAs of most eukaryotic genes are formed by splicing together a series of exons and removing the intervening introns. The identity and order of the exons can vary between mRNAs for the same gene. The alternatively spliced products can generate an increased diversity of protein products. Gueroussov <jats:italic>et al.</jats:italic> show that the alternative splicing of a mammalian splicing regulatory factor affects, in turn, the alternative splicing of a wide range of target RNAs. This regulation mechanism controls a brain-specific alternative splicing program. </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="6250" page="868" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa8381">868</jats:related-article> </jats:p>

<jats:title>Membrane potential regulates growth</jats:title> <jats:p> Changes in electrical potential across the plasma membrane can affect cell growth. Zhou <jats:italic>et al.</jats:italic> discovered that membrane potential influenced the organization of phospholipids in the membrane of cultured mammalian cells and neurons in intact flies (see the Perspective by Accardi). This in turn regulated localization and activity of the small guanine nucleotide binding protein K-Ras, an important regulator of cell proliferation. The cell membrane may thus function analogously to a field-effect transistor by adjusting the strength of mitogenic signaling. </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="6250" page="873" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa5619">873</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6250" page="789" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aad0874">789</jats:related-article> </jats:p>

<jats:title>Transcription factor shape-shifts DNA</jats:title> <jats:p> Controlling when a gene is expressed or repressed is vital for cellular metabolism and development. In <jats:italic>Escherichia coli</jats:italic> , a copper-sensing transcription factor, CueR, can repress or activate expression when bound at exactly the same site in the gene promoter. Philips <jats:italic>et al.</jats:italic> used x-ray crystallography to show that CueR dramatically changes the topology of the DNA upon binding copper but does not affect protein-DNA contacts. The DNA shape change allows RNA polymerase to bind the promoter and transcribe the gene. </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="6250" page="877" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa9809">877</jats:related-article> </jats:p>

<jats:title>Keeping gene transcription in check</jats:title> <jats:p> Transcription of all genes is carried out by RNA polymerase (RNAP). The enzyme is thus a pivotal regulation point for many cell and developmental processes. In bacteria, sigma factors play a vital role in transcription regulation, with σ54 being critical for transcription of many stress response genes. Yang <jats:italic>et al.</jats:italic> determined the x-ray crystal structure of RNAP bound to σ54, as well as promoter DNA. In the initial inhibited state of the RNAP-σ54 complex, the σ54 blocks the template DNA from entering the RNAP active site and the downstream DNA channel. </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="6250" page="882" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab1478">882</jats:related-article> </jats:p>