Making sense of cilia: The role of intraflagellar transport.

Intraflagellar transport (IFT) is essential for both ciliary structure and function. A new study in PLOS Biology reveals how IFT-mediated trafficking and ciliary morphology differentially influence chemosensory responses between neuronal types and among co-expressed receptors.

Targeted deletion of olfactory receptors in via CRISPR/Cas9-mediated LexA knock-in.

The study of olfaction in has greatly benefited from genetic reagents such as olfactory receptor mutant lines and GAL4 reporter lines. The CRISPR/Cas9 gene-editing system has been increasingly used to create null receptor mutants or replace coding regions with GAL4 reporters. To further expand this toolkit for manipulating fly olfactory receptor neurons (ORNs), we generated null alleles for 11 different olfactory receptors by using CRISPR/Cas9 to knock in LexA drivers, including multiple lines for receptors which have thus far lacked knock-in mutants.

Pheromone sensing in Drosophila requires support cell-expressed Osiris 8.

Background: The nose of most animals comprises multiple sensory subsystems, which are defined by the expression of different olfactory receptor families. Drosophila melanogaster antennae contain two morphologically and functionally distinct subsystems that express odorant receptors (Ors) or ionotropic receptors (Irs). Although these receptors have been thoroughly characterized in this species, the subsystem-specific expression and roles of other genes are much less well-understood.

Valence opponency in peripheral olfactory processing.

A hallmark of complex sensory systems is the organization of neurons into functionally meaningful maps, which allow for comparison and contrast of parallel inputs via lateral inhibition. However, it is unclear whether such a map exists in olfaction. Here, we address this question by determining the organizing principle underlying the stereotyped pairing of olfactory receptor neurons (ORNs) in sensory hairs, wherein compartmentalized neurons inhibit each other via ephaptic coupling.

Systematic morphological and morphometric analysis of identified olfactory receptor neurons in .

The biophysical properties of sensory neurons are influenced by their morphometric and morphological features, whose precise measurements require high-quality volume electron microscopy (EM). However, systematic surveys of nanoscale characteristics for identified neurons are scarce. Here, we characterize the morphology of olfactory receptor neurons (ORNs) across the majority of genetically identified sensory hairs.

Distinct Roles and Synergistic Function of Fru Isoforms in Drosophila Olfactory Receptor Neurons.

Sexual dimorphism in Drosophila courtship circuits requires the male-specific transcription factor fru, which is alternatively spliced to encode the Fru, Fru, and Fru isoforms. Most fru-positive neurons express multiple variants; however, the functional significance of their co-expression remains undetermined. Do co-expressed isoforms each play unique roles to jointly regulate dimorphism? By focusing on fru-positive olfactory receptor neurons (ORNs), here, we show that Fru and Fru are both required for males' age-dependent sensitization to aphrodisiac olfactory cues in a cell-autonomous manner.

Neuroscience: Sensing Absolute Cold.

To overwinter, animals must detect constant cold temperatures before adapting their behavior accordingly. A new study in Drosophila describes a circuit mechanism - from sensory neurons to higher brain centers - that encodes and relays persistent, absolute cold stimuli to modulate sleep.

Neuronal Compartmentalization: A Means to Integrate Sensory Input at the Earliest Stage of Information Processing?

In numerous peripheral sense organs, external stimuli are detected by primary sensory neurons compartmentalized within specialized structures composed of cuticular or epithelial tissue. Beyond reflecting developmental constraints, such compartmentalization also provides opportunities for grouped neurons to functionally interact. Here, the authors review and illustrate the prevalence of these structural units, describe characteristics of compartmentalized neurons, and consider possible interactions between these cells.

Amplification of Drosophila Olfactory Responses by a DEG/ENaC Channel.

Insect olfactory receptors operate as ligand-gated ion channels that directly transduce odor stimuli into electrical signals. However, in the absence of any known intermediate transduction steps, it remains unclear whether and how these ionotropic inputs are amplified in olfactory receptor neurons (ORNs). Here, we find that amplification occurs in the Drosophila courtship-promoting ORNs through Pickpocket 25 (PPK25), a member of the degenerin/epithelial sodium channel family (DEG/ENaC).

Electrophysiological Recording from Drosophila Trichoid Sensilla in Response to Odorants of Low Volatility.

Insects rely on their sense of smell to guide a wide range of behaviors that are critical for their survival, such as food-seeking, predator avoidance, oviposition, and mating. Myriad chemicals of varying volatilities have been identified as natural odorants that activate insect Olfactory Receptor Neurons (ORNs). However, studying the olfactory responses to low-volatility odorants has been hampered by an inability to effectively present such stimuli using conventional odor-delivery methods.