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<jats:title>Unnatural Bases</jats:title> <jats:p> The genetic basis of all life on the planet is comprised of deoxyribonucleic acid (DNA) with four nitrogenous nucleotide bases, abbreviated to A, G, C, and T. But there are variations on this theme, and <jats:bold> Pinheiro <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="341" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1217622">341</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="6079" page="307" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1221724">Joyce</jats:related-article> </jats:bold> ) describe the directed evolution of unnatural nucleic acid–like genetic polymers. Variant enzymes were developed that efficiently transcribed DNA to anhydrohexitol (HNA), cyclohexenyl (CeNA), locked (LNA), and threofuranosyl (TNA) nuceic acid analogs. Further variant enzymes were developed to reverse-transcribe these analogs back to DNA. Thus, man-made nucleic acid analogs can be designed and selected that have the potential to operate in a way analogous to the natural process of heredity and evolution. </jats:p>

<jats:title>Ancient Bears</jats:title> <jats:p> Polar bears are well known for adapting to their cold Arctic climate. Some recent studies, based on mitochondrial DNA, concluded that they are a relatively young species and that these adaptations occurred quite quickly. Although mitochondrial DNA is regularly used to estimate evolutionary history, it has some well-known drawbacks, including sex-biased dispersal and hybridization. Thus, <jats:bold> Hailer <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="344" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1216424">344</jats:related-article> ) looked at neutral genetic data that are distributed more widely across the genome of a relatively large sample of polar, brown, and black bears. Consistent with fossil-based studies, the analysis reveals polar bears as a sister lineage to all brown bears, with an estimated divergence time of 300,000 to 900,000 years ago. Thus, polar bears are indeed of a more ancient lineage, and more recent estimates based on mitochondrial DNA are likely to have been affected by past hybridization with brown bear. </jats:p>

<jats:title>Bad News for Bees</jats:title> <jats:p> Neonicotinoid insecticides were introduced in the early 1990s and have become one of the most widely used crop pesticides in the world. These compounds act on the insect central nervous system, and they have been shown to be persistent in the environment and in plant tissues. Recently, there have been controversial connections made between neonicotinoids and pollinator deaths, but the mechanisms underlying these potential deaths have remained unknown. <jats:bold> Whitehorn <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="351" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1215025">351</jats:related-article> , published online 29 March) exposed developing colonies of bumble bees to low levels of the neonicotinoid imidacloprid and then released them to forage under natural conditions. Treated colonies displayed reduced colony growth and less reproductive success, and they produced significantly fewer queens to found subsequent generations. <jats:bold> Henry <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="348" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1215039">348</jats:related-article> , published online 29 March) documented the effects of low-dose, nonlethal intoxication of another widely used neonicotinoid, thiamethoxam, on wild foraging honey bees. Radio-frequency identification tags were used to determine navigation success of treated foragers, which suggested that their homing success was much reduced relative to untreated foragers. </jats:p>

<jats:title>Bad News for Bees</jats:title> <jats:p> Neonicotinoid insecticides were introduced in the early 1990s and have become one of the most widely used crop pesticides in the world. These compounds act on the insect central nervous system, and they have been shown to be persistent in the environment and in plant tissues. Recently, there have been controversial connections made between neonicotinoids and pollinator deaths, but the mechanisms underlying these potential deaths have remained unknown. <jats:bold> Whitehorn <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="351" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1215025">351</jats:related-article> , published online 29 March) exposed developing colonies of bumble bees to low levels of the neonicotinoid imidacloprid and then released them to forage under natural conditions. Treated colonies displayed reduced colony growth and less reproductive success, and they produced significantly fewer queens to found subsequent generations. <jats:bold> Henry <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="348" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1215039">348</jats:related-article> , published online 29 March) documented the effects of low-dose, nonlethal intoxication of another widely used neonicotinoid, thiamethoxam, on wild foraging honey bees. Radio-frequency identification tags were used to determine navigation success of treated foragers, which suggested that their homing success was much reduced relative to untreated foragers. </jats:p>

<jats:title>Climb Every Mountain</jats:title> <jats:p> Mountaintop floras across Europe appear to be responding to climatic change in terms of upslope species range shifts. <jats:bold> Pauli <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="353" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1219033">353</jats:related-article> ) systematically analyzed data gathered from standardized permanent plots on 66 high-mountain environments across Europe. On average, mountaintop species numbers have increased significantly during the last decade. However, this increase is a net effect of gains and losses, with losses particularly affecting mountains of Mediterranean regions and their endemic species. This turnover is largely consistent with model predictions and indicates that high-altitude species, and in particular the rich endemic alpine flora of many Mediterranean mountain ranges, will come under increasing pressure in the predicted warmer and drier climates in this region. </jats:p>

<jats:title>Thoroughly MODern Yeast</jats:title> <jats:p> It is not clear if prion induction in yeast is truly linked to physiological roles. <jats:bold> Suzuki <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="355" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1219491">355</jats:related-article> ) show that the yeast prion protein Mod5 (a transfer RNA isopentenyltransferase) responds to an environmental stressor by converting to an aggregated amyloid form, which leads to phenotypic changes in cell metabolism and drug resistance. Introduction of Mod5 amyloid into yeast resulted in the formation of a dominantly heritable prion state [ <jats:italic>MOD</jats:italic> <jats:sup>+</jats:sup> ], in which Mod5 is aggregated. [ <jats:italic>MOD</jats:italic> <jats:sup>+</jats:sup> ] yeast showed high ergosterol levels and acquired resistance to several antifungal agents. Selective pressure by antifungal drugs on nonprion [ <jats:italic>mod</jats:italic> <jats:sup>−</jats:sup> ] yeast induced the [ <jats:italic>MOD</jats:italic> <jats:sup>+</jats:sup> ] prion state, formation of amyloid, and increased cell survival. </jats:p>

<jats:title>Joint Decisions</jats:title> <jats:p> In many instances, decisions made by relatively homogeneous groups (two or more people) coalesce around the choice that people are most confident in, and this in turn stems from the sampling of representations that individuals perform when making their choices. <jats:bold>Koriat</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="360" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1216549">360</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="6079" page="303" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1221403">Hertwig</jats:related-article> </jats:bold> ) found that if most of the group members are able to form accurate judgments, then confidence and accuracy coincide and the consensus choice is the correct one. By contrast, if few people know the right answer, then heterogeneity in people's representations appeared to offer a surer path to accuracy. </jats:p>

<jats:title>Protein Tipping Point</jats:title> <jats:p> Amyloid fibrils are insoluble protein aggregates that play a role in various degenerative diseases. Recent experiments have provided insight into fibrillar structures; however, the mechanisms of aggregation remain unclear. <jats:bold> Neudecker <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="362" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1214203">362</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="6079" page="308" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1220356">Eliezer</jats:related-article> </jats:bold> ) report the structure of a transient folding intermediate in a protein SH3 domain known to undergo aggregation. The intermediate is stabilized by non-native interactions and exposes an aggregation-prone β strand. Thus, for this protein, folding from the intermediate state will compete with aggregation. </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 synthetic genetics, confidence in decision-making, California's citrus crisis, and more.</jats:p>