A decision underlies phototaxis in an insecticide

Like a moth into the flame-phototaxis is an iconic example for innate preferences. Such preferences probably reflect evolutionary adaptations to predictable situations and have traditionally been conceptualized as hard-wired stimulus-response links. Perhaps for that reason, the century-old discovery of flexibility in Drosophila phototaxis has received little attention. Here, we report that across several different behavioural tests, light/dark preference tested in walking is dependent on various aspects of flight. If we temporarily compromise flying ability, walking photopreference reverses concomitantly. Neuronal activity in circuits expressing dopamine and octopamine, respectively, plays a differential role in photopreference, suggesting a potential involvement of these biogenic amines in this case of behavioural flexibility. We conclude that flies monitor their ability to fly, and that flying ability exerts a fundamental effect on action selection in Drosophila. This work suggests that even behaviours which appear simple and hard-wired comprise a value-driven decision-making stage, negotiating the external situation with the animal's internal state, before an action is selected

Collective action or individual choice: Spontaneity and individuality contribute to decision-making in Drosophila

Our own unique character traits make our behavior consistent and define our individuality. Yet, this consistency does not entail that we behave repetitively like machines. Like humans, animals also combine personality traits with spontaneity to produce adaptive behavior: consistent, but not fully predictable. Here, we study an iconically rigid behavioral trait, insect phototaxis, that nevertheless also contains both components of individuality and spontaneity. In a light/dark T-maze, approximately 70% of a group of Drosophila fruit flies choose the bright arm of the T-Maze, while the remaining 30% walk into the dark. Taking the photopositive and the photonegative subgroups and re-testing them reveals the spontaneous component: a similar 70–30 distribution emerges in each of the two subgroups. Increasing the number of choices to ten choices, reveals the individuality component: flies with an extremely negative series of first choices were more likely to show photonegative behavior in subsequent choices and vice versa. General behavioral traits, independent of light/dark preference, contributed to the development of this individuality. The interaction of individuality and spontaneity together explains why group averages, even for such seemingly stereotypical behaviors, are poor predictors of individual choices

A Functional Misexpression Screen Uncovers a Role for Enabled in Progressive Neurodegeneration

Drosophila is a well-established model to study the molecular basis of neurodegenerative diseases. We carried out a misexpression screen to identify genes involved in neurodegeneration examining locomotor behavior in young and aged flies. We hypothesized that a progressive loss of rhythmic activity could reveal novel genes involved in neurodegenerative mechanisms. One of the interesting candidates showing progressive arrhythmicity has reduced enabled (ena) levels. ena down-regulation gave rise to progressive vacuolization in specific regions of the adult brain. Abnormal staining of pre-synaptic markers such as cystein string protein (CSP) suggest that axonal transport could underlie the neurodegeneration observed in the mutant. Reduced ena levels correlated with increased apoptosis, which could be rescued in the presence of p35, a general Caspase inhibitor. Thus, this mutant recapitulates two important features of human neurodegenerative diseases, i.e., vulnerability of certain neuronal populations and progressive degeneration, offering a unique scenario in which to unravel the specific mechanisms in an easily tractable organism

Phototactic flexibility. Raw data.

<p>Data set from the paper:</p><p>A decision underlies phototaxis in an insect</p

Circadian Pacemaker Neurons Change Synaptic Contacts across the Day

SummaryDaily cycles of rest and activity are a common example of circadian control of physiology. In Drosophila, rhythmic locomotor cycles rely on the activity of 150–200 neurons grouped in seven clusters [1, 2]. Work from many laboratories points to the small ventral lateral neurons (sLNvs) as essential for circadian control of locomotor rhythmicity [3–7]. sLNv neurons undergo circadian remodeling of their axonal projections, opening the possibility for a circadian control of connectivity of these relevant circadian pacemakers [8]. Here we show that circadian plasticity of the sLNv axonal projections has further implications than mere structural changes. First, we found that the degree of daily structural plasticity exceeds that originally described [8], underscoring that changes in the degree of fasciculation as well as extension or pruning of axonal terminals could be involved. Interestingly, the quantity of active zones changes along the day, lending support to the attractive hypothesis that new synapses are formed while others are dismantled between late night and the following morning. More remarkably, taking full advantage of the GFP reconstitution across synaptic partners (GRASP) technique [9], we showed that, in addition to new synapses being added or removed, sLNv neurons contact different synaptic partners at different times along the day. These results lead us to propose that the circadian network, and in particular the sLNv neurons, orchestrates some of the physiological and behavioral differences between day and night by changing the path through which information travels

Mmp1 processing of the PDF neuropeptide regulates circadian structural plasticity of pacemaker neurons

In the Drosophila brain, the neuropeptide PIGMENT DISPERSING FACTOR (PDF) is expressed in the small and large Lateral ventral neurons (LNvs) and regulates circadian locomotor behavior. Interestingly, PDF immunoreactivity at the dorsal terminals changes across the day as synaptic contacts do as a result of a remarkable remodeling of sLNv projections. Despite the relevance of this phenomenon to circuit plasticity and behavior, the underlying mechanisms remain poorly understood. In this work we provide evidence that PDF along with matrix metalloproteinases (Mmp1 and 2) are key in the control of circadian structural remodeling. Adult-specific downregulation of PDF levels per se hampers circadian axonal remodeling, as it does altering Mmp1 or Mmp2 levels within PDF neurons post-developmentally. However, only Mmp1 affects PDF immunoreactivity at the dorsal terminals and exerts a clear effect on overt behavior. In vitro analysis demonstrated that PDF is hydrolyzed by Mmp1, thereby suggesting that Mmp1 could directly terminate its biological activity. These data demonstrate that Mmp1 modulates PDF processing, which leads to daily structural remodeling and circadian behavior

Mmp1 modulates behavioral rhythmicity.

<p><b>A.</b> Representative actograms (<b>left panel</b>) and quantitation of percentage of rhythmicity (<b>right panel</b>) from overexpression experiments. Locomotor activity of individual flies was recorded for 4 days under light-dark cycles and then transferred to constant darkness (gray area) for 9 additional days. Overexpression of Mmp1 or Mmp2 with one UAS copy does not affect circadian locomotor activity. “+” in the x axis refers to a single copy of <i>CD8GFP</i>; <i>pdf</i>-GS. NS, non significant. <b>B.</b> Adult-specific Mmp downregulation trigger opposite effects on locomotor rhythmicity. Silencing Mmp1 but not Mmp2 alters normal circadian locomotor activity. “+” in the x axis refers to a single copy of <i>CD8GFP</i>; <i>pdf</i>-GS. Data represents at least 3 independent experiments and a minimum of 32 flies per Genotype/Condition were analyzed. Different letters indicate statistically significant differences with a p<0.05 (Two-way ANOVA with a Duncan <i>post-hoc</i> test). For other controls and measurements of endogenous period see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004700#pgen.1004700.s007" target="_blank">Table S1</a>.</p

Cell autonomous Mmp1 expression regulates PDF levels.

<p><b>A.</b> Overexpression experiments <b>Left panel.</b> Representative confocal images of PDF immunoreactivity at the dorsal protocerebrum taken during CT2 and CT14 on DD4. <b>Right panel.</b> PDF levels at the dorsal protocerebrum. Control flies exhibit circadian oscillation of PDF levels, while Mmp1 overexpression reduces PDF to levels lower than those observed at nighttime in controls. In contrast, Mmp2 overexpression leads to intermediate levels. “+” in the x axis refers to a single copy of <i>CD8GFP</i>; <i>pdf</i>-GS. <b>B.</b> Downregulation experiments. Reducing Mmp1 but not Mmp2 levels abolishes circadian oscillations in PDF immunoreactivity to constant daytime levels. “+” in the x axis refers to a single copy of <i>CD8GFP</i>, <i>Dcr2</i>; <i>pdf</i>-GS. Data represents the average (± standard error of the mean) of at least 3 independent experiments and a minimum of 23 flies per Genotype/CT were analyzed. Different letters indicate statistically significant differences with a p<0.05 (Two-way ANOVA with a Duncan <i>post-hoc</i> test). In overexpression experiments logarithmic transformation was applied to fulfill ANOVA requirements. In both experiments all the experimental groups include RU to induce expression. Scale: 10 µm.</p