Seasonal timing and molecular evolution of circadian photoresponsive genes in Drosophila

Lead Research Organisation: University of Leicester
Department Name: Genetics

Abstract

In temperate regions, many higher organisms use changes in temperature and daylength (photoperiod) to anticipate the coming season. Daylength is considered a more reliable cue than temperature, and numerous arthropod species, including fruitflies, detect the autumnal shortening of the day to initiate their hibernating (diapause) winter response. Population studies from the northern hemisphere in several insect species have demonstrated that the response to the change in daylength is correlated with latitude, so that northern populations initiate diapause earlier in the year than southern populations, because it gets colder earlier, even though days are still long. Daylength also plays an important role in regulating the daily circadian 24 h rhythms of behaviour and physiology. Northern populations are exposed to extremely long daylengths in the summer, and studies in the laboratory reveal that such light-dark regimes can disrupt circadian behaviour. Several studies have shown that northern populations respond to this challenge by reducing the light-sensitivity of their clock. We have recently analysed natural polymorphism in a gene called timeless (tim) that controls the 24-hour circadian rhythm of behaviour and physiology in the fruit fly. TIM protein is sensitive to light and mediate how the clock responds to light. We have found that a new allele of tim that arose in southern Europe 7-10,000 years ago, is spreading throughout Europe by directional selection. This new tim variant has an attenuated circadian and photoperiodic light response, with the result that in a seasonal environment such as Europe, it anticipates the oncoming winter earlier than flies carrying the tim gene and therefore has a better chance of surviving these harsh conditions. . The reason for this is that the new TIM protein, on stimulation by light, does not physically interact as readily, with a photoreceptor called cryptochrome (CRY). Thus the new mutant tim gene has spread through the population because of its altered photoperiodic behaviour, which in Europe, gives it a competitive advantage, ie Darwinism by natural selection. We have now observed that CRY, and a newly identified protein DAY, which interacts with CRY, and acts to repress its photoceptiveness, show unusually high levels of sequence variation. Some of these changes in the CRY protein make the photoreceptor less photoresponsive. We will examine how these CRY and DAY variants are distributed in Europe, and whether they show the signatures of being maintained by natural selection. We will also extend this approach to the rhodopsin (Rh) genes, which mediate the canonical visual pathway, after a functional assessment of which of the six genes may be the more relevant to diapause. We shall examine the functional consequences of the different cry, day and Rh variants on diapause and circadian light sensitivity, and also study their implications for Darwinian fitness. By correlating genetic variation (and spatial distribution) with phenotypic variation we will identify how populations adapt to different thermal and photoperiodic environments. Our work will have clear implications for developing biological markers for assessing climate change.

Publications

10 25 50
 
Description The ubiquitous circadian clock that drives daily 24 h rhythms in higher eukaryotes is composed of an evolutionary conserved genetic network. Our NERC supported research was aimed at identifying natural adaptive variation in circadian clock genes in Drosophila melanogaster, and exploring how these mutations might accommodate the circadian pacemaker to different environments. Our studies of a natural polymorphism in the clock gene timeless (tim), which were published in back-to-back papers in Science have been selected as a top NERC achievement, and was included in the NERC annual report in 2008. We extended this project by collecting flies from Spain and observing that this allelic variation in tim follows an opposite latitudinal cline to the one we originally reported for the Italian peninsula. This striking result supports our model of directional selection of the newly derived tim allele (as opposed to balancing selection based on a latitudinally associated environmental factor), and confirms the spread of the favoured allele from southern Italy where it was first derived ~3000ya (Zonato et al submitted). We also analysed variation in cryptochrome (cry), a blue-light photoreceptor which is important for circadian function in a broad range of organisms, including plants, insects and mammals. We identified a single nucleotide polymorphism (SNP) that is very common in all European populations and which involves a radical amino-acid change. To test the functional role of this SNP we generated transgenic flies that carry the different cry alleles and found that this polymorphism accounts for substantial variation in various circadian phenotypes. We have analysed the spatial distribution of the cry polymorphism from Scandinavia to the Mediterranean, and found that both alleles are common, which may be driven by photoperiodic-dependent assortative mating (homozygosity increases in Northern latitudes). A manusctipt summarising has been submitted (Pegoraro et al).
Exploitation Route Our finding provided the first molecular link between the circadian clock and the less -studied photoperiodic clock which is critical for seasonal timing. Our study contributed to the rising interest of the chronobiology field in identifying the molecular basis of the photoperiodic clock, which was reflected in the increased number of publications since then. It has also demonstrated the fruit-fly is a powerful model for both the circadian system and for seasonal timing and by that further contributed to replacement and reduction of animal use (the 3R's narrative).
Sectors Agriculture, Food and Drink,Other

 
Description Our finding were highly cited in the scientific litratue and helped in identifying another circadian clock gene. The economic/social impact has not been realized yet.
First Year Of Impact 2007
Sector Other
 
Description H2020-MSCA-ITN-2017
Amount € 3,809,005 (EUR)
Funding ID 765937 
Organisation European Commission H2020 
Sector Public
Country Belgium
Start 05/2018 
End 05/2021
 
Description Light entrainment of the circadian clock: identifying natural molecular adaptations
Amount £293,672 (GBP)
Funding ID BB/G02085X/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 02/2010 
End 01/2013
 
Description Molecular and Cellular Dissection of Morning and Evening Chronotypes in Drosophila melanogaster
Amount £629 (GBP)
Funding ID BB/H018093/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 02/2011 
End 01/2014
 
Description The genetics and genomics of adaptive sex ratio behaviour
Amount £588,581 (GBP)
Funding ID NE/J024481/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 04/2012 
End 03/2015
 
Description Timeless and diapause in Drosophila
Amount £491 (GBP)
Funding ID BB/F014082/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 01/2008 
End 12/2012
 
Title Differential expression of microRNA associated with photoperiod in Drosophila 
Description global expression of microRNA 
Type Of Material Database/Collection of data 
Year Produced 2011 
Provided To Others? Yes  
Impact This is the first demonstration of the role of microRNA in seasonal timing, and regulation of insect diapause. 
 
Title Photoperiodic induction of gene expression in Drosophila 
Description Microarray data 
Type Of Material Database/Collection of data 
Year Produced 2011 
Provided To Others? Yes  
Impact This database provides, for the first time, a list of candidate genes associated with seasonal timing and the photoperiodic response. 
 
Description CINCHRON 
Organisation Academy of Sciences of the Czech Republic
Country Czech Republic 
Sector Learned Society 
PI Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in our laboratory.
Collaborator Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in their laboratory.
Impact MSCA-ITN-ETN award by the Eurpean Comission (proposal number 765937). 3,809,005 EUR.
Start Year 2016
 
Description CINCHRON 
Organisation Hebrew University of Jerusalem
Country Israel 
Sector Academic/University 
PI Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in our laboratory.
Collaborator Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in their laboratory.
Impact MSCA-ITN-ETN award by the Eurpean Comission (proposal number 765937). 3,809,005 EUR.
Start Year 2016
 
Description CINCHRON 
Organisation Jagiellonian University
Country Poland 
Sector Academic/University 
PI Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in our laboratory.
Collaborator Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in their laboratory.
Impact MSCA-ITN-ETN award by the Eurpean Comission (proposal number 765937). 3,809,005 EUR.
Start Year 2016
 
Description CINCHRON 
Organisation National Center for Scientific Research (Centre National de la Recherche Scientifique CNRS)
Country France 
Sector Public 
PI Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in our laboratory.
Collaborator Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in their laboratory.
Impact MSCA-ITN-ETN award by the Eurpean Comission (proposal number 765937). 3,809,005 EUR.
Start Year 2016
 
Description CINCHRON 
Organisation University of Leicester
Department Department of Genetics
Country United Kingdom 
Sector Academic/University 
PI Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in our laboratory.
Collaborator Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in their laboratory.
Impact MSCA-ITN-ETN award by the Eurpean Comission (proposal number 765937). 3,809,005 EUR.
Start Year 2016
 
Description CINCHRON 
Organisation University of Padova
Country Italy 
Sector Academic/University 
PI Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in our laboratory.
Collaborator Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in their laboratory.
Impact MSCA-ITN-ETN award by the Eurpean Comission (proposal number 765937). 3,809,005 EUR.
Start Year 2016
 
Description CINCHRON 
Organisation University of Wurzburg
Country Germany 
Sector Academic/University 
PI Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in our laboratory.
Collaborator Contribution Planning and preparation of the consortium research proposal for a Marie Curie ETN (CINCHRON). Supervision and training of PhD students in their laboratory.
Impact MSCA-ITN-ETN award by the Eurpean Comission (proposal number 765937). 3,809,005 EUR.
Start Year 2016
 
Description 'Plasticity in Circadian Rhythms and Sleep' workshop 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact An invited talk at the 'Plasticity in Circadian Rhythms and Sleep' workshop at the Hebrew University orgenised by the Jerusalem Brain Community. The talk was entitled 'Epigenetic regulation of the photoperiodic clock' and sparked questions and discussion afterwards.
Year(s) Of Engagement Activity 2018
URL https://scholars.huji.ac.il/jbc/event/save-date-jbc-organized-workshop-plasticity-circadian-rhythms-...
 
Description Careers fair and Science Guest Night, Oakham School 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Inroducing genetic research to six-form students at Oakham School

After my visit, a few of the pupils indicate their interest the pursue the studies of genetics at the university.
Year(s) Of Engagement Activity 2009
 
Description School Visit (Haifa) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Giving a lecture on using Drosophila as a model system in genetic research in the local high school. 50 pupils (Year 11) have attended. The school reported increased interest in the related subject area.
Year(s) Of Engagement Activity 2017
 
Description Science Guest Night, Oakham School 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Introducing genetic research to six-form students; talk sparked questions and discussion afterwards.

After my talk, students show interest in visiting my lab.
Year(s) Of Engagement Activity 2012
 
Description Seminar at the University of Veterinary Medicine (Vienna) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation keynote/invited speaker
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Seminar title: Molecular evolution of circadian-clock genes in Drosophila

I am not aware of any impact.
Year(s) Of Engagement Activity 2010
URL http://www.univie.ac.at/evolvienna/?page_id=1260&event_id=37