6 research outputs found
Disrupted Glutamate Signaling in Drosophila Generates Locomotor Rhythms in Constant Light
We have used the Cambridge Protein Trap resource (CPTI) to screen for flies whose
locomotor rhythms are rhythmic in constant light (LL) as a means of identifying circadian
photoreception genes. From the screen of âŒ150 CPTI lines, we obtained seven
hits, two of which targeted the glutamate pathway, Got1 (Glutamate oxaloacetate
transaminase 1) and Gs2 (Glutamine synthetase 2). We focused on these by employing
available mutants and observed that variants of these genes also showed high
levels of LL rhythmicity compared with controls. It was also clear that the genetic
background was important with a strong interaction observed with the common and
naturally occurring timeless (tim) polymorphisms, ls-tim and s-tim. The less circadian
photosensitive ls-tim allele generated high levels of LL rhythmicity in combination with
Got1 or Gs2, even though ls-tim and s-tim alleles do not, by themselves, generate the
LL phenotype. The use of dsRNAi for both genes as well as for Gad (Glutamic acid
decarboxylase) and the metabotropic glutamate receptor DmGluRA driven by clock
gene promoters also revealed high levels of LL rhythmicity compared to controls. It
is clear that the glutamate pathway is heavily implicated in circadian photoreception.
TIM levels in Got1 and Gs2 mutants cycled and were more abundant than in controls
under LL. Got1 but not Gs2 mutants showed diminished phase shifts to 10 min light
pulses. Neurogenetic dissection of the LL rhythmic phenotype using the gal4/gal80 UAS
bipartite system suggested that the more dorsal CRY-negative clock neurons, DNs and
LNds were responsible for the LL phenotype. Immunocytochemistry using the CPTI YFP
tagged insertions for the two genes revealed that the DN1s but not the DN2 and DN3s
expressed Got1 and Gs2, but expression was also observed in the lateral neurons, the
LNds and s-LNvs. Expression of both genes was also found in neuroglia. However,
downregulation of glial Gs2 and Got1 using repo-gal4 did not generate high levels
of LL rhythmicity, so it is unlikely that this phenotype is mediated by glial expression.
Our results suggest a model whereby the DN1s and possibly CRY-negative LNds use
glutamate signaling to supress the pacemaker s-LNvs in LL
The Lutzomyia longipalpis complex: a brief natural history of aggregation-sex pheromone communication
Circadian rhythms in insect disease vectors
Organisms from bacteria to humans have evolved under predictable daily environmental cycles owing to the Earth's rotation. This strong selection pressure has generated endogenous circadian clocks that regulate many aspects of behaviour, physiology and metabolism, anticipating and synchronising internal time-keeping to changes in the cyclical environment. In haematophagous insect vectors the circadian clock coordinates feeding activity, which is important for the dynamics of pathogen transmission. We have recently witnessed a substantial advance in molecular studies of circadian clocks in insect vector species that has consolidated behavioural data collected over many years, which provided insights into the regulation of the clock in the wild. Next generation sequencing technologies will facilitate the study of vector genomes/transcriptomes both among and within species and illuminate some of the species-specific patterns of adaptive circadian phenotypes that are observed in the field and in the laboratory. In this review we will explore these recent findings and attempt to identify potential areas for further investigation