@article{AmatobiOzbekUnalSchaebleretal.2023, author = {Amatobi, Kelechi M. and Ozbek-Unal, Ayten Gizem and Sch{\"a}bler, Stefan and Deppisch, Peter and Helfrich-F{\"o}rster, Charlotte and Mueller, Martin J. and Wegener, Christian and Fekete, Agnes}, title = {The circadian clock is required for rhythmic lipid transport in Drosophila in interaction with diet and photic condition}, series = {Journal of Lipid Research}, volume = {64}, journal = {Journal of Lipid Research}, number = {10}, doi = {10.1016/j.jlr.2023.100417}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-349961}, pages = {100417}, year = {2023}, abstract = {Modern lifestyle is often at odds with endogenously driven rhythmicity, which can lead to circadian disruption and metabolic syndrome. One signature for circadian disruption is a reduced or altered metabolite cycling in the circulating tissue reflecting the current metabolic status. Drosophila is a well-established model in chronobiology, but day-time dependent variations of transport metabolites in the fly circulation are poorly characterized. Here, we sampled fly hemolymph throughout the day and analyzed diacylglycerols (DGs), phosphoethanolamines (PEs) and phosphocholines (PCs) using LC-MS. In wild-type flies kept on sugar-only medium under a light-dark cycle, all transport lipid species showed a synchronized bimodal oscillation pattern with maxima at the beginning and end of the light phase which were impaired in period01 clock mutants. In wild-type flies under constant dark conditions, the oscillation became monophasic with a maximum in the middle of the subjective day. In strong support of clock-driven oscillations, levels of the targeted lipids peaked once in the middle of the light phase under time-restricted feeding independent of the time of food intake. When wild-type flies were reared on full standard medium, the rhythmic alterations of hemolymph lipid levels were greatly attenuated. Our data suggest that the circadian clock aligns daily oscillations of DGs, PEs, and PCs in the hemolymph to the anabolic siesta phase, with a strong influence of light on phase and modality.}, language = {en} } @article{BeckHovhanyanMenegazzietal.2018, author = {Beck, Katherina and Hovhanyan, Anna and Menegazzi, Pamela and Helfrich-F{\"o}rster, Charlotte and Raabe, Thomas}, title = {Drosophila RSK Influences the Pace of the Circadian Clock by Negative Regulation of Protein Kinase Shaggy Activity}, series = {Frontiers in Molecular Neuroscience}, volume = {11}, journal = {Frontiers in Molecular Neuroscience}, number = {122}, issn = {1662-5099}, doi = {10.3389/fnmol.2018.00122}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-196034}, year = {2018}, abstract = {Endogenous molecular circadian clocks drive daily rhythmic changes at the cellular, physiological, and behavioral level for adaptation to and anticipation of environmental signals. The core molecular system consists of autoregulatory feedback loops, where clock proteins inhibit their own transcription. A complex and not fully understood interplay of regulatory proteins influences activity, localization and stability of clock proteins to set the pace of the clock. This study focuses on the molecular function of Ribosomal S6 Kinase (RSK) in the Drosophila melanogaster circadian clock. Mutations in the human rsk2 gene cause Coffin-Lowry syndrome, which is associated with severe mental disabilities. Knock-out studies with Drosophila ortholog rsk uncovered functions in synaptic processes, axonal transport and adult behavior including associative learning and circadian activity. However, the molecular targets of RSK remain elusive. Our experiments provide evidence that RSK acts in the key pace maker neurons as a negative regulator of Shaggy (SGG) kinase activity, which in turn determines timely nuclear entry of the clock proteins Period and Timeless to close the negative feedback loop. Phosphorylation of serine 9 in SGG is mediated by the C-terminal kinase domain of RSK, which is in agreement with previous genetic studies of RSK in the circadian clock but argues against the prevailing view that only the N-terminal kinase domain of RSK proteins carries the effector function. Our data provide a mechanistic explanation how RSK influences the molecular clock and imply SGG S9 phosphorylation by RSK and other kinases as a convergence point for diverse cellular and external stimuli.}, language = {en} } @article{BeerHelfrichFoerster2020, author = {Beer, Katharina and Helfrich-F{\"o}rster, Charlotte}, title = {Model and Non-model Insects in Chronobiology}, series = {Frontiers in Behavioral Neuroscience}, volume = {14}, journal = {Frontiers in Behavioral Neuroscience}, issn = {1662-5153}, doi = {10.3389/fnbeh.2020.601676}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218721}, year = {2020}, abstract = {The fruit fly Drosophila melanogaster is an established model organism in chronobiology, because genetic manipulation and breeding in the laboratory are easy. The circadian clock neuroanatomy in D. melanogaster is one of the best-known clock networks in insects and basic circadian behavior has been characterized in detail in this insect. Another model in chronobiology is the honey bee Apis mellifera, of which diurnal foraging behavior has been described already in the early twentieth century. A. mellifera hallmarks the research on the interplay between the clock and sociality and complex behaviors like sun compass navigation and time-place-learning. Nevertheless, there are aspects of clock structure and function, like for example the role of the clock in photoperiodism and diapause, which can be only insufficiently investigated in these two models. Unlike high-latitude flies such as Chymomyza costata or D. ezoana, cosmopolitan D. melanogaster flies do not display a photoperiodic diapause. Similarly, A. mellifera bees do not go into "real" diapause, but most solitary bee species exhibit an obligatory diapause. Furthermore, sociality evolved in different Hymenoptera independently, wherefore it might be misleading to study the social clock only in one social insect. Consequently, additional research on non-model insects is required to understand the circadian clock in Diptera and Hymenoptera. In this review, we introduce the two chronobiology model insects D. melanogaster and A. mellifera, compare them with other insects and show their advantages and limitations as general models for insect circadian clocks.}, language = {en} } @article{BeerHelfrichFoerster2020, author = {Beer, Katharina and Helfrich-F{\"o}rster, Charlotte}, title = {Post-embryonic Development of the Circadian Clock Seems to Correlate With Social Life Style in Bees}, series = {Frontiers in Cell and Developmental Biology}, volume = {8}, journal = {Frontiers in Cell and Developmental Biology}, issn = {2296-634X}, doi = {10.3389/fcell.2020.581323}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-216450}, year = {2020}, abstract = {Social life style can influence many aspects of an animal's daily life, but it has not yet been clarified, whether development of the circadian clock in social and solitary living bees differs. In a comparative study, with the social honey bee, Apis mellifera, and the solitary mason bee, Osmia bicornis, we now found indications for a differentially timed clock development in social and solitary bees. Newly emerged solitary bees showed rhythmic locomotion right away and the number of neurons in the brain that produce the clock component pigment-dispersing factor (PDF) did not change during aging of the adult solitary bee. Honey bees on the other hand, showed no circadian locomotion directly after emergence and the neuronal clock network continued to grow after emergence. Social bees appear to emerge at an early developmental stage at which the circadian clock is still immature, but bees are already able to fulfill in-hive tasks.}, language = {en} } @article{BeerHaertelHelfrichFoerster2022, author = {Beer, Katharina and H{\"a}rtel, Stephan and Helfrich-F{\"o}rster, Charlotte}, title = {The pigment-dispersing factor neuronal network systematically grows in developing honey bees}, series = {The Journal of Comparative Neurology}, volume = {530}, journal = {The Journal of Comparative Neurology}, number = {9}, doi = {10.1002/cne.25278}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257300}, pages = {1321-1340}, year = {2022}, abstract = {The neuropeptide pigment-dispersing factor (PDF) plays a prominent role in the circadian clock of many insects including honey bees. In the honey bee brain, PDF is expressed in about 15 clock neurons per hemisphere that lie between the central brain and the optic lobes. As in other insects, the bee PDF neurons form wide arborizations in the brain, but certain differences are evident. For example, they arborize only sparsely in the accessory medulla (AME), which serves as important communication center of the circadian clock in cockroaches and flies. Furthermore, all bee PDF neurons cluster together, which makes it impossible to distinguish individual projections. Here, we investigated the developing bee PDF network and found that the first three PDF neurons arise in the third larval instar and form a dense network of varicose fibers at the base of the developing medulla that strongly resembles the AME of hemimetabolous insects. In addition, they send faint fibers toward the lateral superior protocerebrum. In last larval instar, PDF cells with larger somata appear and send fibers toward the distal medulla and the medial protocerebrum. In the dorsal part of the medulla serpentine layer, a small PDF knot evolves from which PDF fibers extend ventrally. This knot disappears during metamorphosis and the varicose arborizations in the putative AME become fainter. Instead, a new strongly stained PDF fiber hub appears in front of the lobula. Simultaneously, the number of PDF neurons increases and the PDF neuronal network in the brain gets continuously more complex.}, language = {en} } @article{BeerJoschinskiSastreetal.2017, author = {Beer, Katharina and Joschinski, Jens and Sastre, Alazne Arrazola and Krauss, Jochen and Helfrich-F{\"o}rster, Charlotte}, title = {A damping circadian clock drives weak oscillations in metabolism and locomotor activity of aphids (Acyrthosiphon pisum)}, series = {Scientific Reports}, volume = {7}, journal = {Scientific Reports}, number = {14906}, doi = {10.1038/s41598-017-15014-3}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170020}, year = {2017}, abstract = {Timing seasonal events, like reproduction or diapause, is crucial for the survival of many species. Global change causes phenologies worldwide to shift, which requires a mechanistic explanation of seasonal time measurement. Day length (photoperiod) is a reliable indicator of winter arrival, but it remains unclear how exactly species measure day length. A reference for time of day could be provided by a circadian clock, by an hourglass clock, or, as some newer models suggest, by a damped circadian clock. However, damping of clock outputs has so far been rarely observed. To study putative clock outputs of Acyrthosiphon pisum aphids, we raised individual nymphs on coloured artificial diet, and measured rhythms in metabolic activity in light-dark illumination cycles of 16:08 hours (LD) and constant conditions (DD). In addition, we kept individuals in a novel monitoring setup and measured locomotor activity. We found that A. pisum is day-active in LD, potentially with a bimodal distribution. In constant darkness rhythmicity of locomotor behaviour persisted in some individuals, but patterns were mostly complex with several predominant periods. Metabolic activity, on the other hand, damped quickly. A damped circadian clock, potentially driven by multiple oscillator populations, is the most likely explanation of our results.}, language = {en} } @article{BeerSchenkHelfrichFoersteretal.2019, author = {Beer, Katharina and Schenk, Mariela and Helfrich-F{\"o}rster, Charlotte and Holzschuh, Andrea}, title = {The circadian clock uses different environmental time cues to synchronize emergence and locomotion of the solitary bee Osmia bicornis}, series = {Scientific Reports}, volume = {9}, journal = {Scientific Reports}, doi = {10.1038/s41598-019-54111-3}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-202721}, pages = {17748}, year = {2019}, abstract = {Life on earth adapted to the daily reoccurring changes in environment by evolving an endogenous circadian clock. Although the circadian clock has a crucial impact on survival and behavior of solitary bees, many aspects of solitary bee clock mechanisms remain unknown. Our study is the first to show that the circadian clock governs emergence in Osmia bicornis, a bee species which overwinters as adult inside its cocoon. Therefore, its eclosion from the pupal case is separated by an interjacent diapause from its emergence in spring. We show that this bee species synchronizes its emergence to the morning. The daily rhythms of emergence are triggered by temperature cycles but not by light cycles. In contrast to this, the bee's daily rhythms in locomotion are synchronized by light cycles. Thus, we show that the circadian clock of O. bicornis is set by either temperature or light, depending on what activity is timed. Light is a valuable cue for setting the circadian clock when bees have left the nest. However, for pre-emerged bees, temperature is the most important cue, which may represent an evolutionary adaptation of the circadian system to the cavity-nesting life style of O. bicornis.}, language = {en} } @article{BeerSteffanDewenterHaerteletal.2016, author = {Beer, Katharina and Steffan-Dewenter, Ingolf and H{\"a}rtel, Stephan and Helfrich-F{\"o}rster, Charlotte}, title = {A new device for monitoring individual activity rhythms of honey bees reveals critical effects of the social environment on behavior}, series = {Journal of Comparative Physiology A}, volume = {202}, journal = {Journal of Comparative Physiology A}, number = {8}, doi = {10.1007/s00359-016-1103-2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-188030}, pages = {555-565}, year = {2016}, abstract = {Chronobiological studies of individual activity rhythms in social insects can be constrained by the artificial isolation of individuals from their social context. We present a new experimental set-up that simultaneously measures the temperature rhythm in a queen-less but brood raising mini colony and the walking activity rhythms of singly kept honey bees that have indirect social contact with it. Our approach enables monitoring of individual bees in the social context of a mini colony under controlled laboratory conditions. In a pilot experiment, we show that social contact with the mini colony improves the survival of monitored young individuals and affects locomotor activity patterns of young and old bees. When exposed to conflicting Zeitgebers consisting of a light-dark (LD) cycle that is phase-delayed with respect to the mini colony rhythm, rhythms of young and old bees are socially synchronized with the mini colony rhythm, whereas isolated bees synchronize to the LD cycle. We conclude that the social environment is a stronger Zeitgeber than the LD cycle and that our new experimental set-up is well suited for studying the mechanisms of social entrainment in honey bees.}, language = {en} } @article{BreitenbachHelfrichFoersterDandekar2021, author = {Breitenbach, Tim and Helfrich-F{\"o}rster, Charlotte and Dandekar, Thomas}, title = {An effective model of endogenous clocks and external stimuli determining circadian rhythms}, series = {Scientific Reports}, volume = {11}, journal = {Scientific Reports}, number = {1}, doi = {10.1038/s41598-021-95391-y}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-261655}, pages = {16165}, year = {2021}, abstract = {Circadian endogenous clocks of eukaryotic organisms are an established and rapidly developing research field. To investigate and simulate in an effective model the effect of external stimuli on such clocks and their components we developed a software framework for download and simulation. The application is useful to understand the different involved effects in a mathematical simple and effective model. This concerns the effects of Zeitgebers, feedback loops and further modifying components. We start from a known mathematical oscillator model, which is based on experimental molecular findings. This is extended with an effective framework that includes the impact of external stimuli on the circadian oscillations including high dose pharmacological treatment. In particular, the external stimuli framework defines a systematic procedure by input-output-interfaces to couple different oscillators. The framework is validated by providing phase response curves and ranges of entrainment. Furthermore, Aschoffs rule is computationally investigated. It is shown how the external stimuli framework can be used to study biological effects like points of singularity or oscillators integrating different signals at once. The mathematical framework and formalism is generic and allows to study in general the effect of external stimuli on oscillators and other biological processes. For an easy replication of each numerical experiment presented in this work and an easy implementation of the framework the corresponding Mathematica files are fully made available. They can be downloaded at the following link: https://www.biozentrum.uni-wuerzburg.de/bioinfo/computing/circadian/.}, language = {en} } @article{ChenReiherHermannLuibletal.2016, author = {Chen, Jiangtian and Reiher, Wencke and Hermann-Luibl, Christiane and Sellami, Azza and Cognigni, Paola and Kondo, Shu and Helfrich-F{\"o}rster, Charlotte and Veenstra, Jan A. and Wegener, Christian}, title = {Allatostatin A Signalling in Drosophila Regulates Feeding and Sleep and Is Modulated by PDF}, series = {PLoS Genetics}, volume = {12}, journal = {PLoS Genetics}, number = {9}, doi = {10.1371/journal.pgen.1006346}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-178170}, year = {2016}, abstract = {Feeding and sleep are fundamental behaviours with significant interconnections and cross-modulations. The circadian system and peptidergic signals are important components of this modulation, but still little is known about the mechanisms and networks by which they interact to regulate feeding and sleep. We show that specific thermogenetic activation of peptidergic Allatostatin A (AstA)-expressing PLP neurons and enteroendocrine cells reduces feeding and promotes sleep in the fruit fly Drosophila. The effects of AstA cell activation are mediated by AstA peptides with receptors homolog to galanin receptors subserving similar and apparently conserved functions in vertebrates. We further identify the PLP neurons as a downstream target of the neuropeptide pigment-dispersing factor (PDF), an output factor of the circadian clock. PLP neurons are contacted by PDF-expressing clock neurons, and express a functional PDF receptor demonstrated by cAMP imaging. Silencing of AstA signalling and continuous input to AstA cells by tethered PDF changes the sleep/activity ratio in opposite directions but does not affect rhythmicity. Taken together, our results suggest that pleiotropic AstA signalling by a distinct neuronal and enteroendocrine AstA cell subset adapts the fly to a digestive energy-saving state which can be modulated by PDF.}, language = {en} } @article{ColizziBeerCutietal.2021, author = {Colizzi, Francesca Sara and Beer, Katharina and Cuti, Paolo and Deppisch, Peter and Mart{\´i}nez Torres, David and Yoshii, Taishi and Helfrich-F{\"o}rster, Charlotte}, title = {Antibodies Against the Clock Proteins Period and Cryptochrome Reveal the Neuronal Organization of the Circadian Clock in the Pea Aphid}, series = {Frontiers in Physiology}, volume = {12}, journal = {Frontiers in Physiology}, issn = {1664-042X}, doi = {10.3389/fphys.2021.705048}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-242909}, year = {2021}, abstract = {Circadian clocks prepare the organism to cyclic environmental changes in light, temperature, or food availability. Here, we characterized the master clock in the brain of a strongly photoperiodic insect, the aphid Acyrthosiphon pisum, immunohistochemically with antibodies against A. pisum Period (PER), Drosophila melanogaster Cryptochrome (CRY1), and crab Pigment-Dispersing Hormone (PDH). The latter antibody detects all so far known PDHs and PDFs (Pigment-Dispersing Factors), which play a dominant role in the circadian system of many arthropods. We found that, under long days, PER and CRY are expressed in a rhythmic manner in three regions of the brain: the dorsal and lateral protocerebrum and the lamina. No staining was detected with anti-PDH, suggesting that aphids lack PDF. All the CRY1-positive cells co-expressed PER and showed daily PER/CRY1 oscillations of high amplitude, while the PER oscillations of the CRY1-negative PER neurons were of considerable lower amplitude. The CRY1 oscillations were highly synchronous in all neurons, suggesting that aphid CRY1, similarly to Drosophila CRY1, is light sensitive and its oscillations are synchronized by light-dark cycles. Nevertheless, in contrast to Drosophila CRY1, aphid CRY1 was not degraded by light, but steadily increased during the day and decreased during the night. PER was always located in the nuclei of the clock neurons, while CRY was predominantly cytoplasmic and revealed the projections of the PER/CRY1-positive neurons. We traced the PER/CRY1-positive neurons through the aphid protocerebrum discovering striking similarities with the circadian clock of D. melanogaster: The CRY1 fibers innervate the dorsal and lateral protocerebrum and putatively connect the different PER-positive neurons with each other. They also run toward the pars intercerebralis, which controls hormone release via the neurohemal organ, the corpora cardiaca. In contrast to Drosophila, the CRY1-positive fibers additionally travel directly toward the corpora cardiaca and the close-by endocrine gland, corpora allata. This suggests a direct link between the circadian clock and the photoperiodic control of hormone release that can be studied in the future.}, language = {en} } @article{DeppischHelfrichFoersterSenthilan2022, author = {Deppisch, Peter and Helfrich-F{\"o}rster, Charlotte and Senthilan, Pingkalai R.}, title = {The gain and loss of cryptochrome/photolyase family members during evolution}, series = {Genes}, volume = {13}, journal = {Genes}, number = {9}, doi = {10.3390/genes13091613}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312873}, year = {2022}, abstract = {The cryptochrome/photolyase (CRY/PL) family represents an ancient group of proteins fulfilling two fundamental functions. While photolyases repair UV-induced DNA damages, cryptochromes mainly influence the circadian clock. In this study, we took advantage of the large number of already sequenced and annotated genes available in databases and systematically searched for the protein sequences of CRY/PL family members in all taxonomic groups primarily focusing on metazoans and limiting the number of species per taxonomic order to five. Using BLASTP searches and subsequent phylogenetic tree and motif analyses, we identified five distinct photolyases (CPDI, CPDII, CPDIII, 6-4 photolyase, and the plant photolyase PPL) and six cryptochrome subfamilies (DASH-CRY, mammalian-type MCRY, Drosophila-type DCRY, cnidarian-specific ACRY, plant-specific PCRY, and the putative magnetoreceptor CRY4. Manually assigning the CRY/PL subfamilies to the species studied, we have noted that over evolutionary history, an initial increase of various CRY/PL subfamilies was followed by a decrease and specialization. Thus, in more primitive organisms (e.g., bacteria, archaea, simple eukaryotes, and in basal metazoans), we find relatively few CRY/PL members. As species become more evolved (e.g., cnidarians, mollusks, echinoderms, etc.), the CRY/PL repertoire also increases, whereas it appears to decrease again in more recent organisms (humans, fruit flies, etc.). Moreover, our study indicates that all cryptochromes, although largely active in the circadian clock, arose independently from different photolyases, explaining their different modes of action.}, language = {en} } @article{DusikSenthilanMentzeletal.2014, author = {Dusik, Verena and Senthilan, Pingkalai R. and Mentzel, Benjamin and Hartlieb, Heiko and W{\"u}lbeck, Corina and Yoshii, Taishi and Raabe, Thomas and Helfrich-F{\"o}rster, Charlotte}, title = {The MAP Kinase p38 Is Part of Drosophila melanogaster's Circadian Clock}, series = {PLoS Genetics}, volume = {10}, journal = {PLoS Genetics}, number = {8}, issn = {1553-7404}, doi = {10.1371/journal.pgen.1004565}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-119433}, pages = {e1004565}, year = {2014}, abstract = {All organisms have to adapt to acute as well as to regularly occurring changes in the environment. To deal with these major challenges organisms evolved two fundamental mechanisms: the p38 mitogen-activated protein kinase (MAPK) pathway, a major stress pathway for signaling stressful events, and circadian clocks to prepare for the daily environmental changes. Both systems respond sensitively to light. Recent studies in vertebrates and fungi indicate that p38 is involved in light-signaling to the circadian clock providing an interesting link between stress-induced and regularly rhythmic adaptations of animals to the environment, but the molecular and cellular mechanisms remained largely unknown. Here, we demonstrate by immunocytochemical means that p38 is expressed in Drosophila melanogaster's clock neurons and that it is activated in a clock-dependent manner. Surprisingly, we found that p38 is most active under darkness and, besides its circadian activation, additionally gets inactivated by light. Moreover, locomotor activity recordings revealed that p38 is essential for a wild-type timing of evening activity and for maintaining ∼ 24 h behavioral rhythms under constant darkness: flies with reduced p38 activity in clock neurons, delayed evening activity and lengthened the period of their free-running rhythms. Furthermore, nuclear translocation of the clock protein Period was significantly delayed on the expression of a dominant-negative form of p38b in Drosophila's most important clock neurons. Western Blots revealed that p38 affects the phosphorylation degree of Period, what is likely the reason for its effects on nuclear entry of Period. In vitro kinase assays confirmed our Western Blot results and point to p38 as a potential "clock kinase" phosphorylating Period. Taken together, our findings indicate that the p38 MAP Kinase is an integral component of the core circadian clock of Drosophila in addition to playing a role in stress-input pathways.}, language = {en} } @article{FischerHelfrichFoersterPeschel2016, author = {Fischer, Robin and Helfrich-F{\"o}rster, Charlotte and Peschel, Nicolai}, title = {GSK-3 Beta Does Not Stabilize Cryptochrome in the Circadian Clock of Drosophila}, series = {PLoS ONE}, volume = {11}, journal = {PLoS ONE}, number = {1}, doi = {10.1371/journal.pone.0146571}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-180370}, year = {2016}, abstract = {Cryptochrome (CRY) is the primary photoreceptor of Drosophila's circadian clock. It resets the circadian clock by promoting light-induced degradation of the clock protein Timeless (TIM) in the proteasome. Under constant light, the clock stops because TIM is absent, and the flies become arrhythmic. In addition to TIM degradation, light also induces CRY degradation. This depends on the interaction of CRY with several proteins such as the E3 ubiquitin ligases Jetlag (JET) and Ramshackle (BRWD3). However, CRY can seemingly also be stabilized by interaction with the kinase Shaggy (SGG), the GSK-3 beta fly orthologue. Consequently, flies with SGG overexpression in certain dorsal clock neurons are reported to remain rhythmic under constant light. We were interested in the interaction between CRY, Ramshackle and SGG and started to perform protein interaction studies in S2 cells. To our surprise, we were not able to replicate the results, that SGG overexpression does stabilize CRY, neither in S2 cells nor in the relevant clock neurons. SGG rather does the contrary. Furthermore, flies with SGG overexpression in the dorsal clock neurons became arrhythmic as did wild-type flies. Nevertheless, we could reproduce the published interaction of SGG with TIM, since flies with SGG overexpression in the lateral clock neurons shortened their free-running period. We conclude that SGG does not directly interact with CRY but rather with TIM. Furthermore we could demonstrate, that an unspecific antibody explains the observed stabilization effects on CRY.}, language = {en} } @article{FujiwaraHermannLuiblKatsuraetal.2018, author = {Fujiwara, Yuri and Hermann-Luibl, Christiane and Katsura, Maki and Sekiguchi, Manabu and Ida, Takanori and Helfrich-F{\"o}rster, Charlotte and Yoshii, Taishi}, title = {The CCHamide1 Neuropeptide Expressed in the Anterior Dorsal Neuron 1 Conveys a Circadian Signal to the Ventral Lateral Neurons in Drosophila melanogaster}, series = {Frontiers in Physiology}, volume = {09}, journal = {Frontiers in Physiology}, issn = {1664-042X}, doi = {10.3389/fphys.2018.01276}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-195940}, year = {2018}, abstract = {The fruit fly Drosophila melanogaster possesses approximately 150 brain clock neurons that control circadian behavioral rhythms. Even though individual clock neurons have self-sustaining oscillators, they interact and synchronize with each other through a network. However, little is known regarding the factors responsible for these network interactions. In this study, we investigated the role of CCHamide1 (CCHa1), a neuropeptide expressed in the anterior dorsal neuron 1 (DN1a), in intercellular communication of the clock neurons. We observed that CCHa1 connects the DN1a clock neurons to the ventral lateral clock neurons (LNv) via the CCHa1 receptor, which is a homolog of the gastrin-releasing peptide receptor playing a role in circadian intercellular communications in mammals. CCHa1 knockout or knockdown flies have a generally low activity level with a special reduction of morning activity. In addition, they exhibit advanced morning activity under light-dark cycles and delayed activity under constant dark conditions, which correlates with an advance/delay of PAR domain Protein 1 (PDP1) oscillations in the small-LNv (s-LNv) neurons that control morning activity. The terminals of the s-LNv neurons show rather high levels of Pigment-dispersing factor (PDF) in the evening, when PDF is low in control flies, suggesting that the knockdown of CCHa1 leads to increased PDF release; PDF signals the other clock neurons and evidently increases the amplitude of their PDP1 cycling. A previous study showed that high-amplitude PDP1 cycling increases the siesta of the flies, and indeed, CCHa1 knockout or knockdown flies exhibit a longer siesta than control flies. The DN1a neurons are known to be receptive to PDF signaling from the s-LNv neurons; thus, our results suggest that the DN1a and s-LNv clock neurons are reciprocally coupled via the neuropeptides CCHa1 and PDF, and this interaction fine-tunes the timing of activity and sleep.}, language = {en} } @article{HornMitesserHovestadtetal.2019, author = {Horn, Melanie and Mitesser, Oliver and Hovestadt, Thomas and Yoshii, Taishi and Rieger, Dirk and Helfrich-F{\"o}rster, Charlotte}, title = {The circadian clock improves fitness in the fruit fly, Drosophila melanogaster}, series = {Frontiers in Physiology}, volume = {10}, journal = {Frontiers in Physiology}, number = {1374}, issn = {1664-042X}, doi = {10.3389/fphys.2019.01374}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-195738}, year = {2019}, abstract = {It is assumed that a properly timed circadian clock enhances fitness, but only few studies have truly demonstrated this in animals. We raised each of the three classical Drosophila period mutants for >50 generations in the laboratory in competition with wildtype flies. The populations were either kept under a conventional 24-h day or under cycles that matched the mutant's natural cycle, i.e., a 19-h day in the case of pers mutants and a 29-h day for perl mutants. The arrhythmic per0 mutants were grown together with wildtype flies under constant light that renders wildtype flies similar arrhythmic as the mutants. In addition, the mutants had to compete with wildtype flies for two summers in two consecutive years under outdoor conditions. We found that wildtype flies quickly outcompeted the mutant flies under the 24-h laboratory day and under outdoor conditions, but perl mutants persisted and even outnumbered the wildtype flies under the 29-h day in the laboratory. In contrast, pers and per0 mutants did not win against wildtype flies under the 19-h day and constant light, respectively. Our results demonstrate that wildtype flies have a clear fitness advantage in terms of fertility and offspring survival over the period mutants and - as revealed for perl mutants - this advantage appears maximal when the endogenous period resonates with the period of the environment. However, the experiments indicate that perl and pers persist at low frequencies in the population even under the 24-h day. This may be a consequence of a certain mating preference of wildtype and heterozygous females for mutant males and time differences in activity patterns between wildtype and mutants.}, language = {en} } @article{JoschinskiBeerHelfrichFoersteretal.2016, author = {Joschinski, Jens and Beer, Katharina and Helfrich-F{\"o}rster, Charlotte and Krauss, Jochen}, title = {Pea Aphids (Hemiptera: Aphididae) Have Diurnal Rhythms When Raised Independently of a Host Plant}, series = {Journal of Insect Science}, volume = {16}, journal = {Journal of Insect Science}, number = {1}, doi = {10.1093/jisesa/iew013}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-168783}, pages = {31}, year = {2016}, abstract = {Seasonal timing is assumed to involve the circadian clock, an endogenous mechanism to track time and measure day length. Some debate persists, however, and aphids were among the first organisms for which circadian clock involvement was questioned. Inferences about links to phenology are problematic, as the clock itself is little investigated in aphids. For instance, it is unknown whether aphids possess diurnal rhythms at all. Possibly, the close interaction with host plants prevents independent measurements of rhythmicity. We reared the pea aphid Acyrthosiphon pisum (Harris) on an artificial diet, and recorded survival, moulting, and honeydew excretion. Despite their plant-dependent life style, aphids were independently rhythmic under light-dark conditions. This first demonstration of diurnal aphid rhythms shows that aphids do not simply track the host plant's rhythmicity.}, language = {en} } @article{ReinhardSchubertBertolinietal.2022, author = {Reinhard, Nils and Schubert, Frank K. and Bertolini, Enrico and Hagedorn, Nicolas and Manoli, Giulia and Sekiguchi, Manabu and Yoshii, Taishi and Rieger, Dirk and Helfrich-F{\"o}rster, Charlotte}, title = {The neuronal circuit of the dorsal circadian clock neurons in Drosophila melanogaster}, series = {Frontiers in Physiology}, volume = {13}, journal = {Frontiers in Physiology}, issn = {1664-042X}, doi = {10.3389/fphys.2022.886432}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-272527}, year = {2022}, abstract = {Drosophila's dorsal clock neurons (DNs) consist of four clusters (DN1as, DN1ps, DN2s, and DN3s) that largely differ in size. While the DN1as and the DN2s encompass only two neurons, the DN1ps consist of ∼15 neurons, and the DN3s comprise ∼40 neurons per brain hemisphere. In comparison to the well-characterized lateral clock neurons (LNs), the neuroanatomy and function of the DNs are still not clear. Over the past decade, numerous studies have addressed their role in the fly's circadian system, leading to several sometimes divergent results. Nonetheless, these studies agreed that the DNs are important to fine-tune activity under light and temperature cycles and play essential roles in linking the output from the LNs to downstream neurons that control sleep and metabolism. Here, we used the Flybow system, specific split-GAL4 lines, trans-Tango, and the recently published fly connectome (called hemibrain) to describe the morphology of the DNs in greater detail, including their synaptic connections to other clock and non-clock neurons. We show that some DN groups are largely heterogenous. While certain DNs are strongly connected with the LNs, others are mainly output neurons that signal to circuits downstream of the clock. Among the latter are mushroom body neurons, central complex neurons, tubercle bulb neurons, neurosecretory cells in the pars intercerebralis, and other still unidentified partners. This heterogeneity of the DNs may explain some of the conflicting results previously found about their functionality. Most importantly, we identify two putative novel communication centers of the clock network: one fiber bundle in the superior lateral protocerebrum running toward the anterior optic tubercle and one fiber hub in the posterior lateral protocerebrum. Both are invaded by several DNs and LNs and might play an instrumental role in the clock network.}, language = {en} } @article{SchlichtingRiegerCusumanoetal.2018, author = {Schlichting, Matthias and Rieger, Dirk and Cusumano, Paola and Grebler, Rudi and Costa, Rodolfo and Mazzotta, Gabriella M. and Helfrich-F{\"o}rster, Charlotte}, title = {Cryptochrome interacts with actin and enhances eye-mediated light sensitivity of the circadian clock in Drosophila melanogaster}, series = {Frontiers in Molecular Neuroscience}, volume = {11}, journal = {Frontiers in Molecular Neuroscience}, number = {238}, doi = {10.3389/fnmol.2018.00238}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-177086}, year = {2018}, abstract = {Cryptochromes (CRYs) are a class of flavoproteins that sense blue light. In animals, CRYs are expressed in the eyes and in the clock neurons that control sleep/wake cycles and are implied in the generation and/or entrainment of circadian rhythmicity. Moreover, CRYs are sensing magnetic fields in insects as well as in humans. Here, we show that in the fruit fly Drosophila melanogaster CRY plays a light-independent role as "assembling" protein in the rhabdomeres of the compound eyes. CRY interacts with actin and appears to increase light sensitivity of the eyes by keeping the "signalplex" of the phototransduction cascade close to the membrane. By this way, CRY also enhances light-responses of the circadian clock.}, language = {en} } @article{SenthilanHelfrichFoerster2016, author = {Senthilan, Pingkalai R. and Helfrich-F{\"o}rster, Charlotte}, title = {Rhodopsin 7-The unusual Rhodopsin in Drosophila}, series = {PeerJ}, volume = {4}, journal = {PeerJ}, doi = {10.7717/peerj.2427}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-177998}, year = {2016}, abstract = {Rhodopsins are the major photopigments in the fruit fly Drosophila melanogaster. Drosophila express six well-characterized Rhodopsins (Rh1-Rh6) with distinct absorption maxima and expression pattern. In 2000, when the Drosophila genome was published, a novel Rhodopsin gene was discovered: Rhodopsin 7 (Rh7). Rh7 is highly conserved among the Drosophila genus and is also found in other arthropods. Phylogenetic trees based on protein sequences suggest that the seven Drosophila Rhodopsins cluster in three different groups. While Rh1, Rh2 and Rh6 form a "vertebrate-melanopsin-type"-cluster, and Rh3, Rh4 and Rh5 form an "insect-type"-Rhodopsin cluster, Rh7 seem to form its own cluster. Although Rh7 has nearly all important features of a functional Rhodopsin, it differs from other Rhodopsins in its genomic and structural properties, suggesting it might have an overall different role than other known Rhodopsins.}, language = {en} }