Latest Articles Include:
- Working for John Maddox
- Current Biology 19(9):R343-R344 (2009)
- Green shoots
- Current Biology 19(9):R345-R346 (2009)
While the UK government presents a budget hoped to tackle economic as well as environmental challenges, other countries have taken the lead in harnessing the economic interventions for ecological gains. Michael Gross reports.
- Adam's antics
- Current Biology 19(9):R346-R347 (2009)
Mediawatch: The activities of Adam, a new robotic laboratory tool, came under scrutiny. Bernard Dixon reports.
- Down the food chain
- Current Biology 19(9):R347-R348 (2009)
Fisheries are increasingly targeting smaller and more unusual species as traditional targets decline and the demand for feed for farmed fish increases. Nigel Williams reports.
- Polar pressures
- Current Biology 19(9):R349-R350 (2009)
The Arctic ice is thinning and tourists are presenting a growing problem in the increasingly fragile Antarctic environment. Nigel Williams reports.
- High-level twitter
- Current Biology 19(9):R350-R351 (2009)
A new study finds that a social bird responds to the position from which it receives information. Nigel Williams reports.
- Panda rebuild
- Current Biology 19(9):R351 (2009)
- Michael Young
- Current Biology 19(9):R352-R353 (2009)
- Mauthner cells
- Current Biology 19(9):R353-R355 (2009)
- Orchestration of the immune response by dendritic cells
- Current Biology 19(9):R355-R361 (2009)
- A simple non-specific chemical signal mediates defence behaviour in a specialised ant–plant mutualism
- Current Biology 19(9):R361-R362 (2009)
Specialist 'plant-ants' defend their ant-plant hosts from herbivores in exchange for rewards, including shelter and food . Many of these symbiotic associations are obligate mutualisms, in which ant fitness is strongly tied to host protection. Protection should be enhanced by efficient detection of attacking herbivores ,  and . How information about herbivore presence could be communicated from plant to ant has been little studied. In several systems, plant extracts have been shown to induce increased ant patrolling  and , but the compounds eliciting ant defence have never been identified. We have characterized the volatile compounds emitted by damaged leaves of a specialized ant-plant and demonstrated in field experiments the identity of chemicals that induce plant-protective behaviour.
- Aging: Shall We Take the High Road?
- Current Biology 19(9):R363-R364 (2009)
For ectotherms, lifespan is increased at low temperature and decreased at high temperature. A new study in Caenorhabditis elegans shows that thermosensory neurons can counteract the effects of high temperature on lifespan by controlling the activity of a steroid signaling pathway.
- Behavioural Ecology: Cuckolder Eggs Come First
- Current Biology 19(9):R364-R366 (2009)
In mixed paternity broods, extra-pair offspring often perform better than their maternal half-siblings. This has been interpreted as evidence for genetic benefits of female promiscuity, but a new study shows that the difference in fitness may be largely due to a non-genetic, maternal effect.
- Animal Behaviour: Feeding the Superorganism
- Current Biology 19(9):R366-R368 (2009)
Insect societies are often described as superorganisms, and there are many functional parallels between organisms and superorganisms. Elegant work using ants shows that nutrient regulation, which occurs in many non-social animals, can also occur at the colony-level.
- Mating-System Evolution: Genies from a Bottleneck
- Current Biology 19(9):R369-R370 (2009)
Evolutionary shifts from outcrossing to selfing have been frequent in plants, but little is known about how this occurs. Two new studies of the same species point to a recent bottleneck that coincided with one such shift.
- Neurobiology: Reconstructing the Neural Control of Leg Coordination
- Current Biology 19(9):R371-R373 (2009)
Walking is adaptable because the timing of movements of individual legs can be varied while maintaining leg coordination. Recent work in stick insects shows that leg coordination set by interactions of pattern generating circuits can be overridden by sensory feedback.
- Multisensory Integration: Frequency Tuning of Audio-Tactile Integration
- Current Biology 19(9):R373-R375 (2009)
Multisensory information can be crucial, yet in many circumstances we have little, if any, awareness of the effects of multisensory inputs on what appear to be entirely unisensory perceptions. A recent study shows robust effects of auditory input on tactile frequency discriminations and that this auditory cross-sensory interference has specific tuning.
- Necrosis: C-Type Lectins Sense Cell Death
- Current Biology 19(9):R375-R378 (2009)
Recent studies have shown that C-type lectins, a family of surface receptors known to recognize microbial carbohydrate moieties, also sense products from dying cells and transduce inflammatory signals that modulate the immune system.
- Social Learning: What Do Drosophila Have to Offer?
- Current Biology 19(9):R378-R380 (2009)
The recent finding that female Drosophila copy the mate-choice criteria of other females introduces a mainstream model species to the study of how animals use social information.
- Signaling Pathways Regulating Zebrafish Lateral Line Development
- Current Biology 19(9):R381-R386 (2009)
The lateral line organ is a mechanosensory organ of fish and amphibians that detects changes in water flow. The lateral line organ of zebrafish has been used as a model for cell polarity and collective cell migration as well as hair cell loss and regeneration. A combination of genetic tools and live imaging has allowed dissection of signaling pathways that regulate these processes. Here, we summarize recent findings on the roles of the FGF, Wnt/beta-catenin, and Notch pathways in the initial formation of the posterior lateral line primordium, as well as during organ patterning, migration, cell fate specification and hair cell regeneration.
- Regulation of the Longevity Response to Temperature by Thermosensory Neurons in Caenorhabditis elegans
- Current Biology 19(9):715-722 (2009)
Background Many ectotherms, including C. elegans, have shorter life spans at high temperature than at low temperature. High temperature is generally thought to increase the "rate of living" simply by increasing chemical reaction rates. In this study, we questioned this view and asked whether the temperature dependence of life span is subject to active regulation. Results We show that thermosensory neurons play a regulatory role in the temperature dependence of life span. Surprisingly, inhibiting the function of thermosensory neurons by mutation or laser ablation causes animals to have even shorter life spans at warm temperature. Thermosensory mutations shorten life span by decreasing expression of daf-9, a gene required for the synthesis of ligands that inhibit the DAF-12, a nuclear hormone receptor. The short life span of thermosensory mutants at warm temperature is completely suppressed by a daf-12(-) mutation. Conclusions Our data suggest that thermosensory neurons affect life span at warm temperature by changing the activity of a steroid-signaling pathway that affects longevity. We propose that this thermosensory system allows C. elegans to reduce the effect that warm temperature would otherwise have on processes that affect aging, something that warm-blooded animals do by controlling temperature itself.
- aPKC Phosphorylates Miranda to Polarize Fate Determinants during Neuroblast Asymmetric Cell Division
- Current Biology 19(9):723-729 (2009)
Background Asymmetric cell divisions generate daughter cells with distinct fates by polarizing fate determinants into separate cortical domains. Atypical protein kinase C (aPKC) is an evolutionarily conserved regulator of cell polarity. In Drosophila neuroblasts, apically restricted aPKC is required for segregation of neuronal differentiation factors such as Numb and Miranda to the basal cortical domain. Whereas Numb is polarized by direct aPKC phosphorylation, Miranda asymmetry is thought to occur via a complicated cascade of repressive interactions (aPKC −| Lgl −| myosin II −| Miranda). Results Here we provide biochemical, cellular, and genetic data showing that aPKC directly phosphorylates Miranda to exclude it from the cortex and that Lgl antagonizes this activity. Miranda is phosphorylated by aPKC at several sites in its cortical localization domain and phosphorylation is necessary and sufficient for cortical displacement, suggesting that the repressive-cascade model is incorrect. In investigating key results that led to this model, we found that Y-27632, a Rho kinase inhibitor used to implicate myosin II, efficiently inhibits aPKC. Lgl3A, a nonphosphorylatable Lgl variant used to implicate Lgl in this process, inhibits the formation of apical aPKC crescents in neuroblasts. Furthermore, Lgl directly inhibits aPKC kinase activity. Conclusions Miranda polarization during neuroblast asymmetric cell division occurs by displacement from the apical cortex by direct aPKC phosphorylation. Rather than mediating Miranda cortical displacement, Lgl instead promotes aPKC asymmetry by regulating its activity. The role of myosin II in neuroblast polarization, if any, is unknown.
- Public Versus Personal Information for Mate Copying in an Invertebrate
- Current Biology 19(9):730-734 (2009)
Organisms require information to make decisions about fitness-affecting resources, such as mates. Animals may extract "personal information" about potential mates by observing their physical characteristics or extract additional "public information" by observing their mating performance . Mate copying by females , , ,  and  is a form of public information use that may reduce uncertainty about male quality, allowing more adaptive choices . Experimental studies have produced evidence that female mate copying occurs in several species of fish , birds ,  and , and mammals , including humans . We report the first evidence that a female invertebrate can exploit public information to select mates. In a first experiment, Drosophila melanogaster female prospectors increased their time in the attraction zones of poor-condition males, but not of good-condition males, after having observed them with a model female. This suggests that ! females appraised prospective mates by exploiting public information and did so mainly when it contrasted with personal information. In a second experiment, prospector females preferably mated with males of the color type they had previously observed copulating over males of the rejected color type, suggesting that female Drosophila can generalize socially learned information. The complexity of Drosophila decision-making suggests an unprecedented level of cognition in invertebrates. Our findings have implications for evolution given that socially learned mate preferences may lead to reproductive isolation, setting the stage for speciation .
- Audiovisual Integration of Speech in a Bistable Illusion
- Current Biology 19(9):735-739 (2009)
Visible speech enhances the intelligibility of auditory speech when listening conditions are poor , and can modify the perception of otherwise perfectly audible utterances . This audiovisual perception is our most natural form of communication and one of our most common multisensory phenomena. However, where and in what form the visual and auditory representations interact is still not completely understood. Although there are longstanding proposals that multisensory integration occurs relatively late in the speech-processing sequence , considerable neurophysiological evidence suggests that audiovisual interactions can occur in the brain stem and primary sensory cortices  and . A difficulty testing such hypotheses is that when the degree of integration is manipulated experimentally, the visual and/or auditory stimulus conditions are drastically modified  and ; thus, the perceptual processing within a modality and the corresponding processing loads ! are affected . Here, we used a bistable speech stimulus to examine the conditions under which there is a visual influence on auditory perception in speech. The results indicate that visual influences on auditory speech processing, at least for the McGurk illusion, necessitate the conscious perception of the visual speech gestures, thus supporting the hypothesis that multisensory speech integration is not completed in early processing stages.
- Communal Nutrition in Ants
- Current Biology 19(9):740-744 (2009)
Studies on nonsocial insects have elucidated the regulatory strategies employed to meet nutritional demands ,  and . However, how social insects maintain the supply of an appropriate balance of nutrients at both a collective and an individual level remains unknown. Sociality complicates nutritional regulatory strategies ,  and . First, the food entering a colony is collected by a small number of workers, which need to adjust their harvesting strategy to the demands for nutrients among individuals within the colony , ,  and . Second, because carbohydrates are used by the workers and proteins consumed by the larvae , , , , , ,  and , nutritional feedbacks emanating from both must exist and be integrated to determine food exploitation by foragers , , ,  and . Here, we show that foraging ants can solve nutritional challenges for the colony by making intricate adjustments to their feeding behavior a! nd nutrient processing, acting both as a collective mouth and gut. The amount and balance of nutrients collected and the precision of regulation depend on the presence of larvae in the colony. Ants improved the macronutrient balance of collected foods by extracting carbohydrates and ejecting proteins. Nevertheless, processing excess protein shortened life span—an effect that was greatly ameliorated in the presence of larvae.
- Motion Aftereffects Transfer between Touch and Vision
- Current Biology 19(9):745-750 (2009)
Current views on multisensory motion integration assume separate substrates where visual motion perceptually dominates tactile motion  and . However, recent neuroimaging findings demonstrate strong activation of visual motion processing areas by tactile stimuli , ,  and , implying a potentially bidirectional relationship. To test the relationship between visual and tactile motion processing, we examined the transfer of motion aftereffects. In the well-known visual motion aftereffect, adapting to visual motion in one direction causes a subsequently presented stationary stimulus to be perceived as moving in the opposite direction  and . The existence of motion aftereffects in the tactile domain was debated ,  and , though robust tactile motion aftereffects have recently been demonstrated  and . By using a motion adaptation paradigm, we found that repeated exposure to visual motion in a given direction produced a tactile motion a! ftereffect, the illusion of motion in the opponent direction across the finger pad. We also observed that repeated exposure to tactile motion induces a visual motion aftereffect, biasing the perceived direction of counterphase gratings. These crossmodal aftereffects, operating both from vision to touch and from touch to vision, present strong behavioral evidence that the processing of visual and tactile motion rely on shared representations that dynamically impact modality-specific perception.
- Seminal Fluid Protein Allocation and Male Reproductive Success
- Current Biology 19(9):751-757 (2009)
Postcopulatory sexual selection can select for sperm allocation strategies in males  and , but males should also strategically allocate nonsperm components of the ejaculate  and , such as seminal fluid proteins (Sfps). Sfps can influence the extent of postcopulatory sexual selection ,  and , but little is known of the causes or consequences of quantitative variation in Sfp production and transfer. Using Drosophila melanogaster, we demonstrate that Sfps are strategically allocated to females in response to the potential level of sperm competition. We also show that males who can produce and transfer larger quantities of specific Sfps have a significant competitive advantage. When males were exposed to a competitor male, matings were longer and more of two key Sfps, sex peptide  and ovulin , were transferred, indicating strategic allocation of Sfps. Males selected for large accessory glands (a major site of Sfp synthesis) produced and transferr! ed significantly more sex peptide, but not more ovulin. Males with large accessory glands also had significantly increased competitive reproductive success. Our results show that quantitative variation in specific Sfps is likely to play an important role in postcopulatory sexual selection and that investment in Sfp production is essential for male fitness in a competitive environment.
- ICIS and Aurora B Coregulate the Microtubule Depolymerase Kif2a
- Current Biology 19(9):758-763 (2009)
Kinesins in the mitotic spindle play major roles in determining spindle shape, size, and bipolarity, although specific regulation of these kinesins at distinct locations on the spindle is poorly understood. So that the forces that are required for spindle bipolarity are balanced, microtubule-depolymerizing kinesins are tightly regulated. Aurora B kinase phosphorylates the neck regions of the kinesin-13 family microtubule depolymerases Kif2a and mitotic centromere-associated kinesin (MCAK) and inhibits their depolymerase activities. How they are reactivated and how this is controlled independently on different kinetochore fibers is unknown. We show that inner centromere Kin-I stimulator (ICIS), which stimulates the related depolymerase MCAK, can reactivate Kif2a after Aurora B inhibition. When antibodies that block the ability of ICIS to activate Kif2a are injected into cells, monopolar spindles are generated. This phenotype is rescued by coinjection of anti-Nuf2 antibo! dies. We have performed a structure-function analysis of the ICIS protein and find that the N terminus of ICIS binds Aurora B and its regulators INCENP and TD60, whereas a central region binds MCAK, Kif2a, and microtubules, suggesting a scaffold function for ICIS. These data argue that ICIS and the chromosomal passenger complex (CPC) regulate Kif2a depolymerase activity.
- Host Mixing and Disease Emergence
- Current Biology 19(9):764-767 (2009)
Recent cases of emergent diseases have renewed interest in the evolutionary and ecological mechanisms that promote parasite adaptation to novel hosts , , , ,  and . Crucial to adaptation is the degree of mixing of original, susceptible hosts, and novel hosts. An increase in the frequency of the original host has two opposing effects on adaptation: an increase in the supply of mutant pathogens with improved performance on the novel host ,  and ; and reduced selection to infect novel hosts, caused by fitness costs commonly observed to be associated with host switching , , , , , ,  and . The probability of disease emergence will therefore peak at intermediate frequencies of the original host. We tested these predictions by following the evolution of a virus grown under a range of different frequencies of susceptible (original) and resistant (novel) host bacteria. Viruses that evolved to infect resistant hosts were! only detected when susceptible hosts were at frequencies between 0.1% and 1%. Subsequent experiments supported the predictions that there was reduced selection and mutation supply at higher and lower frequencies, respectively. These results suggest that adaptation to novel hosts can occur only under very specific ecological conditions, and that small changes in contact rates between host species might help to mitigate disease emergence.
- Bcl-2 Proteins EGL-1 and CED-9 Do Not Regulate Mitochondrial Fission or Fusion in Caenorhabditis elegans
- Current Biology 19(9):768-773 (2009)
The Bcl-2 family proteins are critical apoptosis regulators that associate with mitochondria and control the activation of caspases. Recently, both mammalian and C. elegans Bcl-2 proteins have been implicated in controlling mitochondrial fusion and fission processes in both living and apoptotic cells. To better understand the potential roles of Bcl-2 family proteins in regulating mitochondrial dynamics, we carried out a detailed analysis of mitochondria in animals that either lose or have increased activity of egl-1 and ced-9, two Bcl-2 family genes that induce and inhibit apoptosis in C. elegans, respectively. Unexpectedly, we found that loss of egl-1 or ced-9, or overexpression of their gene products, had no apparent effect on mitochondrial connectivity or mitochondrial size. Moreover, loss of ced-9 did not affect the mitochondrial morphology observed in a drp-1 mutant, in which mitochondrial fusion occurs but mitochondrial fission is defective, or in a fzo-1 mutant,! in which mitochondrial fission occurs but mitochondrial fusion is restricted, suggesting that ced-9 is not required for either the mitochondrial fission or fusion process in C. elegans. Taken together, our results argue against an evolutionarily conserved role for Bcl-2 proteins in regulating mitochondrial fission and fusion.
- Five siRNAs Targeting Three SNPs May Provide Therapy for Three-Quarters of Huntington's Disease Patients
- Current Biology 19(9):774-778 (2009)
Among dominant neurodegenerative disorders, Huntington's disease (HD) is perhaps the best candidate for treatment with small interfering RNAs (siRNAs) , , , , , , ,  and . Invariably fatal, HD is caused by expansion of a CAG repeat in the Huntingtin gene, creating an extended polyglutamine tract that makes the Huntingtin protein toxic . Silencing mutant Huntingtin messenger RNA (mRNA) should provide therapeutic benefit, but normal Huntingtin likely contributes to neuronal function ,  and . No siRNA strategy can yet distinguish among the normal and disease Huntingtin alleles and other mRNAs containing CAG repeats . siRNAs targeting the disease isoform of a heterozygous single-nucleotide polymorphism (SNP) in Huntingtin provide an alternative , , ,  and . We sequenced 22 predicted SNP sites in 225 human samples corresponding to HD and control subjects. We find that 48% of our patient population is heteroz! ygous at a single SNP site; one isoform of this SNP is associated with HD. Several other SNP sites are frequently heterozygous. Consequently, five allele-specific siRNAs, corresponding to just three SNP sites, could be used to treat three-quarters of the United States and European HD patient populations. We have designed and validated selective siRNAs for the three SNP sites, laying the foundation for allele-specific RNA interference (RNAi) therapy for HD.
- A Novel Peptide Mediates Aggregation and Migration of Hemocytes from an Insect
- Current Biology 19(9):779-785 (2009)
Insect blood cells (hemocytes) comprise an essential arm of the immune system , , , , ,  and . Several factors mediating recognition and phagocytosis of foreign intruders by hemocytes have been identified, but the mechanisms regulating hemocyte movement remain fragmentary. Embryonic hemocytes from Drosophila migrate along stereotypical routes in response to chemotactic signals from PVF ligands, members of the platelet-derived growth factor family , , ,  and . Embryonic and larval hemocytes also accumulate at external wounds ,  and , but PVFs are not required for this response, suggesting involvement by other, unknown factors. Here we report the identification of hemocyte chemotactic peptide (HCP) from the moth Pseudaletia separata and present evidence that it stimulates aggregation and directed movement of phagocytic hemocytes. Spatiotemporal studies revealed that HCP is expressed in both epidermal cells and hemocytes,! whereas structure-function studies identified post-translational modifications important for activity. HCP also shares similarities with another group of cytokines from moths called ENF peptides , ,  and . Taken together, our results identify HCP as a chemotactic cytokine that enhances clotting at wound sites in larvae.
- In Vivo Detection of Residues Required for Ligand-Selective Activation of the S-Locus Receptor in Arabidopsis
- Current Biology 19(9):786-791 (2009)
The self-incompatibility response of crucifers is a barrier to fertilization in which arrest of pollen tube development is mediated by allele-specific interactions between polymorphic receptors and ligands encoded by the S-locus haplotype. Activation of stigma-expressed S-locus receptor kinase (SRK)  by pollen coat-localized S-locus cysteine-rich (SCR) ligand , ,  and  and the resulting rejection of pollen occurs only if receptor and ligand are encoded by the same S haplotype , ,  and . To identify residues within the SRK extracellular domain (eSRK) that are required for its ligand-selective activation, we assayed chimeric receptors and receptor variants containing substitutions at polymorphic sites in Arabidopsis thaliana  and . We show that only a small number of the not, vert, similar100 polymorphic residues in eSRK are required for ligand-specific activation of self-incompatibility in vivo. These essential residues occur in two non! contiguous clusters located at equivalent positions in the two variants tested. They also correspond to sites showing elevated levels of substitutions in other SRKs, suggesting that these residues could define self-incompatibility specificity in most SRKs. The results demonstrate that the majority of eSRK residues that show signals of positive selection and previously surmised to function as specificity determinants are not essential for specificity in the SRK-SCR interaction.
- Maternal Effects Contribute to the Superior Performance of Extra-Pair Offspring
- Current Biology 19(9):792-797 (2009)
The explanation for extra-pair mating in female birds remains poorly understood and contentious , , , , ,  and . Several leading hypotheses propose that females benefit indirectly by enhancing the genetic quality of their offspring, through good genes or genetic compatibility effects ,  and . Supporting this idea, recent studies have identified a range of fitness-related traits for which extra-pair offspring (EPO) are superior to their within-pair (WP) half-siblings , , , , , , , , , ,  and . However, such performance differences may result from nongenetic maternal effects if EPO are positioned earlier in the laying order and benefit from the advantages of earlier hatching  and . Here we show that EPO are larger, heavier, and more likely to fledge than their WP half-siblings in a population of blue tits, Cyanistes caeruleus. However, extra-pair paternity declined markedly with laying ! order, resulting in EPO generally hatching earlier. After correcting for variation in hatch time, none of the observed disparities between EPO and their WP half-siblings remained significant. These findings indicate that phenotypic comparisons between maternal half-siblings must consider potential hatching-order effects and suggest that the evidence for genetic benefits from extra-pair copulation may be less compelling than currently accepted. Moreover, the overrepresentation of EPO early in the laying order may help explain female extra-pair mating.
- Enhanced Arrestin Facilitates Recovery and Protects Rods Lacking Rhodopsin Phosphorylation
- Current Biology 19(9):798 (2009)
- Regulation of the Longevity Response to Temperature by Thermosensory Neurons in Caenorhabditis elegans
- Current Biology 19(9):798 (2009)