Disorder in convergent floral nanostructures enhances signalling to bees.

Diverse forms of nanoscale architecture generate structural colour and perform signalling functions within and between species. Structural colour is the result of the interference of light from approximately regular periodic structures; some structural disorder is, however, inevitable in biological organisms. Is this disorder functional and subject to evolutionary selection, or is it simply an unavoidable outcome of biological developmental processes? Here we show that disordered nanostructures enable flowers to produce visual signals that are salient to bees. These disordered nanostructures (identified in most major lineages of angiosperms) have distinct anatomies but convergent optical properties; they all produce angle-dependent scattered light, predominantly at short wavelengths (ultraviolet and blue). We manufactured artificial flowers with nanoscale structures that possessed tailored levels of disorder in order to investigate how foraging bumblebees respond to this optical effect. We conclude that floral nanostructures have evolved, on multiple independent occasions, an effective degree of relative spatial disorder that generates a photonic signature that is highly salient to insect pollinators.

Conical petal epidermal cells, regulated by the MYB transcription factor MIXTA, have an ancient origin within the angiosperms.

Conical epidermal cells occur on the tepals (perianth organs, typically petals and/or sepals) of the majority of animal-pollinated angiosperms, where they play both visual and tactile roles in pollinator attraction, providing grip to foraging insects, and enhancing colour, temperature, and hydrophobicity. To explore the evolutionary history of conical epidermal cells in angiosperms, we surveyed the tepal epidermis in representative species of the ANA-grade families, the early-diverging successive sister lineages to all other extant angiosperms, and analysed the function of a candidate regulator of cell outgrowth from Cabomba caroliniana (Nymphaeales). We identified conical cells in at least two genera from different families (Austrobaileya and Cabomba). A single SBG9 MYB gene was isolated from C. caroliniana and found to induce strong differentiation of cellular outgrowth, including conical cells, when ectopically expressed in Nicotiana tabacum. Ontogenetic analysis and quantitative reverse transcription-PCR established that CcSBG9A1 is spatially and temporally expressed in a profile which correlates with a role in conical cell development. We conclude that conical or subconical cells on perianth organs are ancient within the angiosperms and most probably develop using a common genetic programme initiated by a SBG9 MYB transcription factor.

Virus Infection of Plants Alters Pollinator Preference: A Payback for Susceptible Hosts?

Plant volatiles play important roles in attraction of certain pollinators and in host location by herbivorous insects. Virus infection induces changes in plant volatile emission profiles, and this can make plants more attractive to insect herbivores, such as aphids, that act as viral vectors. However, it is unknown if virus-induced alterations in volatile production affect plant-pollinator interactions. We found that volatiles emitted by cucumber mosaic virus (CMV)-infected tomato (Solanum lycopersicum) and Arabidopsis thaliana plants altered the foraging behaviour of bumblebees (Bombus terrestris). Virus-induced quantitative and qualitative changes in blends of volatile organic compounds emitted by tomato plants were identified by gas chromatography-coupled mass spectrometry. Experiments with a CMV mutant unable to express the 2b RNA silencing suppressor protein and with Arabidopsis silencing mutants implicate microRNAs in regulating emission of pollinator-perceivable volatiles. In tomato, CMV infection made plants emit volatiles attractive to bumblebees. Bumblebees pollinate tomato by 'buzzing' (sonicating) the flowers, which releases pollen and enhances self-fertilization and seed production as well as pollen export. Without buzz-pollination, CMV infection decreased seed yield, but when flowers of mock-inoculated and CMV-infected plants were buzz-pollinated, the increased seed yield for CMV-infected plants was similar to that for mock-inoculated plants. Increased pollinator preference can potentially increase plant reproductive success in two ways: i) as female parents, by increasing the probability that ovules are fertilized; ii) as male parents, by increasing pollen export. Mathematical modeling suggested that over a wide range of conditions in the wild, these increases to the number of offspring of infected susceptible plants resulting from increased pollinator preference could outweigh underlying strong selection pressures favoring pathogen resistance, allowing genes for disease susceptibility to persist in plant populations. We speculate that enhanced pollinator service for infected individuals in wild plant populations might provide mutual benefits to the virus and its susceptible hosts.

Pointillist structural color in Pollia fruit.

Biological communication by means of structural color has existed for at least 500 million years. Structural color is commonly observed in the animal kingdom, but has been little studied in plants. We present a striking example of multilayer-based strong iridescent coloration in plants, in the fruit of Pollia condensata. The color is caused by Bragg reflection of helicoidally stacked cellulose microfibrils that form multilayers in the cell walls of the epicarp. We demonstrate that animals and plants have convergently evolved multilayer-based photonic structures to generate colors using entirely distinct materials. The bright blue coloration of this fruit is more intense than that of any previously described biological material. Uniquely in nature, the reflected color differs from cell to cell, as the layer thicknesses in the multilayer stack vary, giving the fruit a striking pixelated or pointillist appearance. Because the multilayers form with both helicoidicities, optical characterization reveals that the reflected light from every epidermal cell is polarized circularly either to the left or to the right, a feature that has never previously been observed in a single tissue.

Oriented protein adsorption to gold nanoparticles through a genetically encodable binding motif.

Simple, stable, and specific methods for immobilizing proteins on gold surfaces are needed for the development of applications that rely on the oriented attachment of proteins to gold surfaces. We report a direct, stable, genetically encodable method for the oriented chemisorption of proteins to gold nanoparticles (Au NPs) through the tetracysteine motif (C-C-P-G-C-C) while simultaneously suppressing protein physisorption. Mutants of ubiquitin (Ub) and enhanced green fluorescent protein (eGFP) containing the tetracysteine motif were produced and displayed stronger adsorption to the NPs than did native proteins. An eGFP mutant with a dicysteine motif (G-C-C) did not show a significant improvement in binding to Au NPs compared to that of the wild-type protein. The binding of the proteins to Au NPs of various sizes (14, 18, 28, and 39 nm) was explored. The small Ub tetracysteine mutant stabilized several sizes of Au NPs, and the eGFP tetracysteine mutant clearly had the strongest chemisorption to the 18 nm NPs. The control of binding orientation for proteins bearing a tetracysteine motif was demonstrated through the enhanced specific binding of protein-NP conjugates to immobilized targets.

Gay and bisexual men's willingness to receive anal Papanicolaou testing.

OBJECTIVES: We assessed the willingness of gay and bisexual men, who have high rates of anal cancer that might be prevented through regular screening, to receive anal Papanicolaou tests. METHODS: We surveyed a national sample of men aged 18 to 59 years who self-identified as gay (n = 236) or bisexual (n = 70). RESULTS: Most respondents were willing to accept free screening (83%), but fewer would pay for the test (31%; McNemar's chi(2) = 158.02; P < .001). Willingness to pay for screening was higher among men who reported greater worry about getting anal cancer (OR [odds ratio] = 1.70; 95% confidence interval [CI] = 1.06, 2.72), higher perceived likelihood of anal cancer (OR = 1.88; 95% CI = 1.18, 2.99), and higher income (OR = 2.17; 95% CI = 1.18, 3.98), in adjusted analyses. Only 33% (17 of 51) of HIV-positive respondents, who have the highest risk for anal cancer, had received anal Papanicolaou tests. CONCLUSIONS: Anal cancer screening was highly acceptable to gay and bisexual men, although cost was a major barrier. Efforts to reduce anal cancer disparities should target beliefs about anal cancer and barriers to anal Papanicolaou testing in this population.

Flower Iridescence Increases Object Detection in the Insect Visual System without Compromising Object Identity.

Iridescence is a form of structural coloration, produced by a range of structures, in which hue is dependent on viewing angle [1-4]. One of these structures, the diffraction grating, is found both in animals (for example, beetles [2]) and in plants (on the petals of some animal pollinated flowers [5]). The behavioral impacts of floral iridescence and its potential ecological significance are unknown [6-9]. Animal-pollinated flowers are described as "sensory billboards" [10], with many floral features contributing to a conspicuous display that filters prospective pollinators. Yet floral iridescence is more subtle to the human eye than that of many animal displays because the floral diffraction grating is not perfectly regular [5-9]. This presents a puzzle: if the function of petals is to attract pollinators, then flowers might be expected to optimize iridescence to increase showiness. On the other hand, pollinators memorize floral colors as consistent advertisements of reward quality, and iridescence might corrupt flower color identity. Here we tested the trade-off between flower detectability and recognition, requiring bumblebees (Bombus terrestris) to identify artificial flowers that varied in pigmentation and degree of iridescence. We find that iridescence does increase target detectability but that "perfect" iridescence (produced by an artificial diffraction grating) corrupts target identity and bees make many mistakes. However, "imperfect" floral iridescence does not lead to mistaken target identity, while still benefitting flower detectability. We hypothesize that similar trade-offs might be found in the many naturally "imperfect" iridescence-producing structures found in animal-animal, as well as other plant-animal, interactions.

Screening for tuberculosis among orphans in a developing country.

BACKGROUND: There has been a recent resurgence of tuberculosis (TB) as a worldwide public health concern. It is a well-documented health problem in Haiti, where the reported prevalence is 123.9 per 100,000 population. While the Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) policy papers for the eradication of TB recommend screening in shelters, prisons, and other congregate-living facilities, screening in institutional orphanages is not specifically mentioned. METHODS: A total of 445 orphans with no documentation of Bacillus Calmette-Guerin (BCG) vaccine at six orphanages representing urban, suburban, and rural Haiti were screened for TB using standardized purified protein derivative (PPD). An inoculum of 0.1 cc was introduced intradermally, with site checks for induration at 48-72 hours after inoculation. Induration >5 mm was recorded as positive. Active cases of TB were defined by symptoms such as fever, night sweats, cough greater than 1 month, or signs of extrapulmonary TB (like scrofula or Pott's disease). RESULTS: The number of positive PPD tests was 170 of the 445 children tested, or 38,202 per 100,000; there were 10 active cases. The overall prevalence of tuberculin positivity in the three orphanages with one or more active cases was 44%, compared to 13% in the three with no identified active cases. CONCLUSIONS: The data indicate that TB prevalence among the orphans screened was 1123 per 100,000. This is substantially greater than that reported for the general Haitian population. These data thus suggest children living in orphanages as a previously unidentified high-risk group for TB infection. Further investigation of TB is recommended for orphans in developing countries.

Sub-chronic treatment with an extract of Hypericum perforatum (St John's wort) significantly reduces cortisol and corticosterone in the rat brain.

Extracts of Hypericum perforatum (HP) have been shown to be effective for the treatment of mild to moderate depression. Its mode of action has not been fully elucidated. An increase in plasma and cerebrospinal fluid (CSF) cortisol is frequently observed in depression. Studies have suggested that HP might alter brain cortisol and corticosterone through its effect on multidrug transporter glycoprotein (Pgp). We investigated the effect of sub-chronic treatment with an extract of HP (LI 160) on brain levels of corticosterone and cortisol in the rat. Results show that HP significantly reduced corticosterone and cortisol in brain frontal cortex tissue. These changes are not reflected in serum. These findings may be important with respect to HPs mode of antidepressant action.

Impairment of central leptin-mediated PI3K signaling manifested as hepatic steatosis independent of hyperphagia and obesity.

Hepatic steatosis is generally thought to develop via peripheral mechanisms associated with obesity. We show that chronic central infusion of leptin suppresses hepatic lipogenic gene expression and reduces triglyceride content via stimulation of hepatic sympathetic activity. This leptin function is independent of feeding and body weight but requires phosphatidylinositol 3-kinase (PI3K) signaling. Attenuation of leptin-induced PI3K signaling, brought about by transgenic expression of phosphatase and tensin homolog (PTEN) in leptin receptor neurons, leads to decreased hepatic sympathetic tone and increased triglyceride levels without affecting adiposity or hepatic insulin signaling. Central leptin's effects on hepatic norepinephrine levels and triglyceride content are blunted in these mutant mice. Simultaneous downregulation of PI3K and signal transducer and activator of transcription-3 (Stat3) in leptin receptor neurons does not exacerbate obesity but causes more severe hepatic steatosis. Together, our results indicate that central cellular leptin resistance in PI3K signaling manifests as hepatic steatosis without causing obesity.

Functional role of suppressor of cytokine signaling 3 upregulation in hypothalamic leptin resistance and long-term energy homeostasis.

OBJECTIVE: Hypothalamic leptin resistance is found in most common forms of obesity, such as diet-induced obesity, and is associated with increased expression of suppressor of cytokine signaling 3 (Socs3) in the hypothalamus of diet-induced obese animals. This study aims to determine the functional consequence of Socs3 upregulation on leptin signaling and obesity, and to investigate whether Socs3 upregulation affects energy balance in a cell type-specific way. RESEARCH DESIGN AND METHODS: We generated transgenic mice overexpressing Socs3 in either proopiomelanocortin (POMC) or leptin receptor-expressing neurons, at levels similar to what is observed in diet-induced obesity. RESULTS: Upregulation of Socs3 in POMC neurons leads to impairment of STAT3 and mammalian target of rapamycin (mTOR)-S6K-S6 signaling, with subsequent leptin resistance, obesity, and glucose intolerance. Unexpectedly, Socs3 upregulation in leptin receptor neurons results in increased expression of STAT3 protein in mutant hypothalami, but does not lead to obesity. CONCLUSIONS: Our study establishes that Socs3 upregulation alone in POMC neurons is sufficient to cause leptin resistance and obesity. Socs3 upregulation impairs both STAT3 and mTOR signaling before the onset of obesity. The lack of obesity in mice with upregulated Socs3 in leptin receptor neurons suggests that Socs3's effect on energy balance could be cell type specific. Our study indicates that POMC neurons are important mediators of Socs3's effect on leptin resistance and obesity, but that other cell types or alteration of other signaling regulators could contribute to the development of obesity.