Pheromone representation in the ant antennal lobe changes with age.

While the neural basis of age-related decline has been extensively studied (1-3), less is known about changes in neural function during the pre-senescent stages of adulthood. Adult neural plasticity is likely a key factor in social insect age polyethism, where individuals perform different tasks as they age and divide labor in an age-dependent manner (4-9). Primarily, workers transition from nursing to foraging tasks (5, 10), become more aggressive, and more readily display alarm behavior (11-16) as they get older. While it is unknown how these behavioral dynamics are neurally regulated, they could partially be generated by altered salience of behaviorally relevant stimuli (4, 6, 7). Here, we investigated how odor coding in the antennal lobe (AL) changes with age in the context of alarm pheromone communication in the clonal raider ant (Ooceraea biroi) (17). Similar to other social insects (11, 12, 16), older ants responded more rapidly to alarm pheromones, the chemical signals for danger. Using whole-AL calcium imaging (18), we then mapped odor representations for five general odorants and two alarm pheromones in young and old ants. Alarm pheromones were represented sparsely at all ages. However, alarm pheromone responses within individual glomeruli changed with age, either increasing or decreasing. Only two glomeruli became sensitized to alarm pheromones with age, while at the same time becoming desensitized to general odorants. Our results suggest that the heightened response to alarm pheromones in older ants occurs via increased sensitivity in these two core glomeruli, illustrating the importance of sensory modulation in social insect division of labor and age-associated behavioral plasticity.

Unselfish meiotic drive maintains heterozygosity in a parthenogenetic ant.

According to Mendel's second law, chromosomes segregate randomly in meiosis. Nonrandom segregation is primarily known for cases of selfish meiotic drive in females, in which particular alleles bias their own transmission into the oocyte1,2. Here, we report a rare example of unselfish meiotic drive for crossover inheritance in the clonal raider ant, Ooceraea biroi. This species produces diploid offspring parthenogenetically via fusion of two haploid nuclei from the same meiosis3. This process should cause rapid genotypic degeneration due to loss of heterozygosity, which results if crossover recombination is followed by random (Mendelian) segregation of chromosomes4,5. However, by comparing whole genomes of mothers and daughters, we show that loss of heterozygosity is exceedingly rare, raising the possibility that crossovers are infrequent or absent in O. biroi meiosis. Using a combination of cytology and whole genome sequencing, we show that crossover recombination is, in fact, common, but that loss of heterozygosity is avoided because crossover products are faithfully co-inherited. This results from a programmed violation of Mendel's law of segregation, such that crossover products segregate together rather than randomly. This discovery highlights an extreme example of cellular "memory" of crossovers, which could be a common yet cryptic feature of chromosomal segregation.

Integration of metabolism and regulation reveals rapid adaptability to growth on non-native substrates.

Engineering synthetic heterotrophy is a key to the efficient bio-based valorization of renewable and waste substrates. Among these, engineering hemicellulosic pentose utilization has been well-explored in Saccharomyces cerevisiae (yeast) over several decades-yet the answer to what makes their utilization inherently recalcitrant remains elusive. Through implementation of a semi-synthetic regulon, we find that harmonizing cellular and engineering objectives are a key to obtaining highest growth rates and yields with minimal metabolic engineering effort. Concurrently, results indicate that "extrinsic" factors-specifically, upstream genes that direct flux of pentoses into central carbon metabolism-are rate-limiting. We also reveal that yeast metabolism is innately highly adaptable to rapid growth on non-native substrates and that systems metabolic engineering (i.e., functional genomics, network modeling, etc.) is largely unnecessary. Overall, this work provides an alternate, novel, holistic (and yet minimalistic) approach based on integrating non-native metabolic genes with a native regulon system.

Sparse and stereotyped encoding implicates a core glomerulus for ant alarm behavior.

Ants communicate via large arrays of pheromones and possess expanded, highly complex olfactory systems, with antennal lobes in the brain comprising up to ∼500 glomeruli. This expansion implies that odors could activate hundreds of glomeruli, which would pose challenges for higher-order processing. To study this problem, we generated transgenic ants expressing the genetically encoded calcium indicator GCaMP in olfactory sensory neurons. Using two-photon imaging, we mapped complete glomerular responses to four ant alarm pheromones. Alarm pheromones robustly activated ≤6 glomeruli, and activity maps for the three pheromones inducing panic alarm in our study species converged on a single glomerulus. These results demonstrate that, rather than using broadly tuned combinatorial encoding, ants employ precise, narrowly tuned, and stereotyped representations of alarm pheromones. The identification of a central sensory hub glomerulus for alarm behavior suggests that a simple neural architecture is sufficient to translate pheromone perception into behavioral outputs.

An oxytocin/vasopressin-related neuropeptide modulates social foraging behavior in the clonal raider ant.

Oxytocin/vasopressin-related neuropeptides are highly conserved and play major roles in regulating social behavior across vertebrates. However, whether their insect orthologue, inotocin, regulates the behavior of social groups remains unknown. Here, we show that in the clonal raider ant Ooceraea biroi, individuals that perform tasks outside the nest have higher levels of inotocin in their brains than individuals of the same age that remain inside the nest. We also show that older ants, which spend more time outside the nest, have higher inotocin levels than younger ants. Inotocin thus correlates with the propensity to perform tasks outside the nest. Additionally, increasing inotocin pharmacologically increases the tendency of ants to leave the nest. However, this effect is contingent on age and social context. Pharmacologically treated older ants have a higher propensity to leave the nest only in the presence of larvae, whereas younger ants seem to do so only in the presence of pupae. Our results suggest that inotocin signaling plays an important role in modulating behaviors that correlate with age, such as social foraging, possibly by modulating behavioral response thresholds to specific social cues. Inotocin signaling thereby likely contributes to behavioral individuality and division of labor in ant societies.

Cardiovascular effects of preeclampsia.

PURPOSE OF REVIEW: Preeclampsia complicates 3-5% of first and 15% of subsequent pregnancies. This study reviews the evidence of increase cardiovascular risk in these women. RECENT FINDINGS: Women with preeclampsia are at two-fold higher risk for development of coronary artery disease, stroke and death, and four-fold increased risk of heart failure. Preeclampsia developed in early part of pregnancy confers greater risk than later in pregnancy. Common factors that predispose women to preeclampsia also confer high risk for developing cardiovascular disease include obesity, metabolic abnormalities, dyslipidaemia, insulin resistance, heightened inflammatory responses, hypercoagulable states and endothelia dysfunction. SUMMARY: Patients with preeclampsia should be screened at regular intervals by a preventive cardiologist and treated accordingly.