Single mutation to a sex pheromone receptor provides adaptive specificity between closely related moth species

Sex pheromone communication, acting as a prezygotic barrier to mating, is believed to have contributed to the speciation of moths and butterflies in the order Lepidoptera. Five decades after the discovery of the first moth sex pheromone, little is known about the molecular mechanisms that underlie the evolution of pheromone communication between closely related species. Although Asian and European corn borers (ACB and ECB) can be interbred in the laboratory, they are behaviorally isolated from mating naturally by their responses to subtly different sex pheromone isomers, (E)-12- and (Z)-12-tetradecenyl acetate and (E)-11- and (Z)-11-tetradecenyl acetate (ACB: E12, Z12; ECB; E11, Z11). Male moth olfactory systems respond specifically to the pheromone blend produced by their conspecific females. In vitro, ECB(Z) odorant receptor 3 (OR3), a sex pheromone receptor expressed in male antennae, responds strongly to E11 but also generally to the Z11, E12, and Z12 pheromones. In contrast, we show that ACB OR3, a gene that has been subjected to positive selection (ω = 2.9), responds preferentially to the ACB E12 and Z12 pheromones. In Ostrinia species the amino acid residue corresponding to position 148 in transmembrane domain 3 of OR3 is alanine (A), except for ACB OR3 that has a threonine (T) in this position. Mutation of this residue from A to T alters the pheromone recognition pattern by selectively reducing the E11 response ∼14-fold. These results suggest that discrete mutations that narrow the specificity of more broadly responsive sex pheromone receptors may provide a mechanism that contributes to speciation

Do Frogs Get Their Kicks on Route 66? Continental U.S. Transect Reveals Spatial and Temporal Patterns of Batrachochytrium dendrobatidis Infection

The chytrid fungus Batrachochytrium dendrobatidis (Bd) has been devastating amphibians globally. Two general scenarios have been proposed for the nature and spread of this pathogen: Bd is an epidemic, spreading as a wave and wiping out individuals, populations, and species in its path; and Bd is endemic, widespread throughout many geographic regions on every continent except Antarctica. To explore these hypotheses, we conducted a transcontinental transect of United States Department of Defense (DoD) installations along U.S. Highway 66 from California to central Illinois, and continuing eastward to the Atlantic Seaboard along U.S. Interstate 64 (in sum from Marine Corps Base Camp Pendleton in California to Naval Air Station Oceana in Virginia). We addressed the following questions: 1) Does Bd occur in amphibian populations on protected DoD environments? 2) Is there a temporal pattern to the presence of Bd? 3) Is there a spatial pattern to the presence of Bd? and 4) In these limited human-traffic areas, is Bd acting as an epidemic (i.e., with evidence of recent introduction and/or die-offs due to chytridiomycosis), or as an endemic (present without clinical signs of disease)? Bd was detected on 13 of the 15 bases sampled. Samples from 30 amphibian species were collected (10% of known United States' species); half (15) tested Bd positive. There was a strong temporal (seasonal) component; in total, 78.5% of all positive samples came in the first (spring/early-summer) sampling period. There was also a strong spatial component—the eleven temperate DoD installations had higher prevalences of Bd infection (20.8%) than the four arid (<60 mm annual precipitation) bases (8.5%). These data support the conclusion that Bd is now widespread, and promote the idea that Bd can today be considered endemic across much of North America, extending from coast-to-coast, with the exception of remote pockets of naïve populations

Selective Permeability of Truncated Aquaporin 1 in Silico

Aquaporin (AQP) proteins function as highly efficient water transport channels that support homeostasis in many types of living cells. Their structure–function relationships have been characterized extensively in fundamental and applied research, primarily via structural analysis, mutational studies, and computational approaches. The present study evaluates the effects of progressive truncations on the permeability and ionic conductivity of AQP-1 (bovine). The use of truncations to determine critical features has not been considered previously, as physical truncation of AQP is likely not technically feasible due to the ornate arrangement of six interwoven alpha helices in a single pore structure. However, structures not obtainable through protein assembly can be realized via synthetic chemistry approaches and studied using molecular dynamics (MD) simulations. Here, we apply the MD method to characterize the permeability of AQP variants truncated along the pore axis from both cytoplasmic and extracellular sides of the channel. The simulation results suggest that AQP-1 can retain its function even after deletion of up to 50% of the channel’s length, representing 50% of proteins’ molecular mass. Deletions such as these are expected to greatly simplify future biomimicry efforts of reproducing the AQP functionality using synthetic macromolecules. This study demonstrates the potential of in silico approaches to support the creation of streamlined functional analogues of biological molecular machines

A list of species sampled for the presence of Bd, organized by families (bold); salamanders followed by frogs.

<p>Asterisks indicate species where at least one specimen tested positive. Thirty species were tested, which represents about 10% of the species found in North America. Frog species are disproportionately representented.</p

Department of Defense installations sampled in the present study.

<p>From California to Illinois, bases (yellow dots) were located near Route 66; from Illinois east to the coast, sites were chosen near Interstate 64 to hold latitude relatively constant (between 33° and 39° N). Our transect is shown overlain on a redrawn United States portion of the Global <i>Bd</i>-Mapping Project <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022211#pone.0022211-Bd1" target="_blank">[14]</a>, with red pins indicating positive sites, white pins indicating negative sites, and blue pins indicating negative sites with sample sizes unknown.</p

Mean annual precipitation (cm) and temperature (°C) at each of the fifteen DoD installations sampled.

<p>These data are plotted against <i>Bd</i> infection rates at each base in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022211#pone-0022211-g002" target="_blank">Figure 2</a>.</p

Summary of percent <i>Bd</i>-positive amphibians detected at each DoD installation for each of the three 2009 sampling periods.

<p>Bases are arranged geographically, as they occur from west to east (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022211#pone-0022211-g001" target="_blank">Fig. 1</a>).</p

Temporal pattern (seasonality) of <i>Bd</i> infection incidence across all installations.

<p>Note the strong tendency for the highest incidences to occur during the spring/early summer sampling period, followed by a precipitous drop off during the mid- to late-summer and fall.</p

Prevalence (percentage) of <i>Bd</i>-positive samples by installation.

<p>Bases are arranged from west to east in the order they appear in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022211#pone-0022211-g001" target="_blank">Figure 1</a>. Right side y-axis indicates both mean annual temperature (°C, yellow line) and mean annual precipitation (cm, red line). Note the generally low percentage of positive samples from the arid western installations.</p