In this issue of Fly

On the Evolution of Multiple Mating pp. 3–11

In this issue of Fly, Gowaty discusses predictions of hypotheses based on sex differences in costs of reproduction. Gowaty et al. have previously showed that polyandry in Drosophila pseudoobscura females may be explained by a series of observations, such as, (1) a single ejaculate was inadequate for lifetime egg production; (2) polyandry provided fitness benefits to females beyond provision of adequate sperm and (3) fitness benefits of polyandry were not offset by costs.

Microtubules at the Cell Cortex pp. 12–5

The microtubule cytoskeleton rapidly and locally reorganizes itself in response to intra- and extracellular signals. The cell cortex represents the major interface between the microtubule cytoskeleton and the extracellular environment. Now, Sharp et al. discuss their recent findings in which Kat-60, a microtubule-severing enzyme and plus-end depolymerase, actively suppresses microtubule growth and stability along the cell edge. This localized activity could feed into larger regulatory pathways, influencing cell polarization and motility.

Discussing Protein Evolution pp. 16–20

In this issue of Fly, Callahan discusses a recent study in which whole-genome comparison of orthologous molecular sequences from closely related Drosophilids was used to explore selective correlations and selective interactions between the amino acids within a protein. The study found a selective length scale of ten amino acids within which individual amino acids are substantially and generically more likely to both share selective pressures and interact epistatically.

Phagocytosis of Bacterial Pathogens pp. 21–5

Phagocytic cells recognize invading microbes and destroy them after internalization, a process required for survival to bacterial infections. Chung and Kocks recently discovered that Eater, a receptor expressed exclusively on Drosophila phagocytes, can defend fruit flies against different kinds of bacteria. Their results suggest that cationic antimicrobial peptides, as well as lysozymes, can facilitate Eater binding to live Gram-negative bacteria, favoring surface exposure of bacterial ligands. The authors propose that unmasking ligands for phagocytic receptors may be a conserved mechanism operating in many animals, including humans.

Balancing the Sex Chromosome Act pp. 26–9

The process of dosage compensation equalizes gene expression between the two sexes, which carry different number of sex chromosomes. In early Drosophila development, when the dosage difference is still unregulated, sex determination mechanisms seem to take advantage of this transient state in order to control sex. Horabin summarizes recent work that suggests that the male-specific dosage compensation is required in Drosophila females and discusses the implications it has for early X chromosome gene expression.

Insights into Notch Proteolysis pp. 30–4

Notch signaling is integral to a large number of developmental and homeostasis events, and either gain or loss of Notch signaling results in a wide range of defects. In order to mediate downstream signaling, Notch must be processed by several proteases, including members of the ADAM family. In this issue of Fly, Christian reviews the interaction of Notch with specific ADAM family members. While ADAM10 is known to be specifically essential for development and homeostasis of mouse epidermis and cardiovascular structures, ADAM17 may not be able to fully replace ADAM10 in these contexts. Recent studies have revealed that ADAM10 is necessary for Notch processing when Notch is activated by a ligand, while ADAM17 is the major protease for processing Notch that is activated independently of ligand in both flies and mammals.

Anger Management in the Fly pp. 35–48

Aggression is a complex behavior widely present throughout the animal kingdom, influenced by a broad range of genetic and environmental factors. Aggressive actions are crucial to ensure survival and reproduction and, in some species, to establish a social hierarchy. Callaerts et al. review recent studies in Drosophila that provide insight into the genetic basis and control of aggression.

Studying the Fourth pp. 49–56

The fourth chromosome of Drosophila is one of the most difficult regions of the fly genome to genetically analyze. One reason for this is that it does not undergo meiotic recombination, which makes recombination mapping impossible, preventing the use of techniques that rely on recombination. In this issue of Fly, Sousa-Neves and Schinaman present a new method that overcomes these limitations and allows the generation of single Minute haplo-4 clones of any fourth chromosome mutant gene in tissues of developing and adult flies.

Sodium Channels, Development, Reproduction and Aging pp. 57–67

Voltage-gated Na⁺ channels are complex membrane proteins responsible for the generation and propagation of the electrical signals through the brain, the skeletal muscle and the heart. The levels of sodium channels affect behavior and physical activity. In this issue of Fly, Garber et al. studied mle^nap-ts mutant flies, which display decreased levels of voltage-gated Na⁺ channels that cause temperature-sensitive paralysis. mle^nap-ts flies appear to be sensitive to temperatures above and below normal environmental conditions and exhibit developmental lethality, decreased fecundity and increased neurodegeneration.