Two or Four Bristles: Functional Evolution of an Enhancer of scute in Drosophilidae

Changes in cis-regulatory sequences are proposed to underlie much of morphological evolution. Yet, little is known about how such modifications translate into phenotypic differences. To address this problem, we focus on the dorsocentral bristles of Drosophilidae. In Drosophila melanogaster, development of these bristles depends on a cis-regulatory element, the dorsocentral enhancer, to activate scute in a cluster of cells from which two bristles on the posterior scutum arise. A few species however, such as D. quadrilineata, bear anterior dorsocentral bristles as well as posterior ones, a derived feature. This correlates with an anterior expansion of the scute expression domain. Here, we show that the D. quadrilineata enhancer has evolved, and is now active in more anterior regions. When used to rescue scute expression in transgenic D. melanogaster, the D. quadrilineata enhancer is able to induce anterior bristles. Importantly, these properties are not displayed by homologous enhancers from control species bearing only two posterior bristles. We also provide evidence that upstream regulation of the enhancer, by the GATA transcription factor Pannier, has been evolutionarily conserved. This work illustrates how, in the context of a conserved trans-regulatory landscape, evolutionary tinkering of pre-existing enhancers can modify gene expression patterns and contribute to morphological diversification

Presenilin Controls CBP Levels in the Adult Drosophila Central Nervous System

Background: Dominant mutations in both human Presenilin (Psn) genes have been correlated with the formation of amyloid plaques and development of familial early-onset Alzheimer’s disease (AD). However, a definitive mechanism whereby plaque formation causes the pathology of familial and sporadic forms of AD has remained elusive. Recent discoveries of several substrates for Psn protease activity have sparked alternative hypotheses for the pathophysiology underlying AD. CBP (CREB-binding protein) is a haplo-insufficient transcriptional co-activator with histone acetly-transferase (HAT) activity that has been proposed to be a downstream target of Psn signaling. Individuals with altered CBP have cognitive deficits that have been linked to several neurological disorders. Methodology/Principal Findings: Using a transgenic RNA-interference strategy to selectively silence CBP, Psn, and Notch in adult Drosophila, we provide evidence for the first time that Psn is required for normal CBP levels and for maintaining specific global acetylations at lysine 8 of histone 4 (H4K8ac) in the central nervous system (CNS). In addition, flies conditionally compromised for the adult-expression of CBP display an altered geotaxis behavior that may reflect a neurological defect. Conclusions/Significance: Our data support a model in which Psn regulates CBP levels in the adult fly brain in a manner that is independent of Notch signaling. Although we do not understand the molecular mechanism underlying th

The Neuropeptide PDF Acts Directly on Evening Pacemaker Neurons to Regulate Multiple Features of Circadian Behavior

Animals use distinct sets of clock neurons to time behaviors in the morning and evening. In this article, the direct neural targets for morning neurons and the neuropeptide pigment dispersing factor are revealed in the fruit fly

The Circadian Neuropeptide PDF Signals Preferentially through a Specific Adenylate Cyclase Isoform AC3 in M Pacemakers of Drosophila

To synchronize a network of pacemakers in the Drosophila brain, a neuropeptide receptor specifically associates with adenylate cyclase 3 to create a “circadian signalosome.

Role for Circadian Clock Genes in Seasonal Timing: Testing the Bunning Hypothesis

A major question in chronobiology focuses around the “Bünning hypothesis” which implicates the circadian clock in photoperiodic (day-length) measurement and is supported in some systems (e.g. plants) but disputed in others. Here, we used the seasonally-regulated thermotolerance of Drosophila melanogaster to test the role of various clock genes in day-length measurement. In Drosophila, freezing temperatures induce reversible chill coma, a narcosis-like state. We have corroborated previous observations that wild-type flies developing under short photoperiods (winter-like) exhibit significantly shorter chill-coma recovery times (CCRt) than flies that were raised under long (summer-like) photoperiods. Here, we show that arrhythmic mutant strains, per01, tim01 and ClkJrk, as well as variants that speed up or slow down the circadian period, disrupt the photoperiodic component of CCRt. Our results support an underlying circadian function mediating seasonal daylength measurement and indicate that clock genes are tightly involved in photo- and thermo-periodic measurements

Immissionsmessungen von faserigen Stäuben in der Bundesrepublik Deutschland. Faserige Immissionen in der Umgebung von Objekten und Gebäuden mit asbesthaltigem Baumaterial

Immissionen von faserigen Stäuben wurden in den Jahren 1983 - 1985 in der nahen Umgebung von Gebäuden mit abwitterten und korrodierten Asbestzement-Produkten durchgeführt. Die Asbestfaserkonzentration (Fasern länger als 5 mym) lagen im Bereich von 50 - 5000 Fasern/cbm. (IUCT