title: Early evolution of the land plant circadian clock.
abstract: While angiosperm clocks can be described as an intricate network of interlocked transcriptional feedback loops, clocks of green algae have been modelled as a loop of only two genes. To investigate the transition from a simple clock in algae to a complex one in angiosperms, we performed an inventory of circadian clock genes in bryophytes and charophytes. Additionally, we performed functional characterization of putative core clock genes in the liverwort Marchantia polymorpha and the hornwort Anthoceros agrestis. Phylogenetic construction was combined with studies of spatiotemporal expression patterns and analysis of M. polymorpha clock gene mutants. Homologues to core clock genes identified in Arabidopsis were found not only in bryophytes but also in charophytes, albeit in fewer copies. Circadian rhythms were detected for most identified genes in M. polymorpha and A. agrestis, and mutant analysis supports a role for putative clock genes in M. polymorpha. Our data are in line with a recent hypothesis that adaptation to terrestrial life occurred earlier than previously expected in the evolutionary history of charophyte algae. Both gene duplication and acquisition of new genes was important in the evolution of the plant circadian clock, but gene loss has also contributed to shaping the clock of bryophytes.
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden.|The Linnean Centre for Plant Biology in Uppsala, Uppsala, Sweden.
authors.forename: Anna-Malin
authors.initials: AM
authors.lastname: Linde
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden.|The Linnean Centre for Plant Biology in Uppsala, Uppsala, Sweden.
authors.forename: D Magnus
authors.identifier: http://orcid.org/0000-0002-0576-7636
authors.initials: DM
authors.lastname: Eklund
authors.affiliation: Graduate School of Biostudies, Kyoto University, Kyoto, 606-8502, Japan.
authors.forename: Akane
authors.initials: A
authors.lastname: Kubota
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden.|The Linnean Centre for Plant Biology in Uppsala, Uppsala, Sweden.
authors.forename: Eric R A
authors.initials: ERA
authors.lastname: Pederson
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden.|The Linnean Centre for Plant Biology in Uppsala, Uppsala, Sweden.
authors.forename: Karl
authors.initials: K
authors.lastname: Holm
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden.|The Linnean Centre for Plant Biology in Uppsala, Uppsala, Sweden.
authors.forename: Niclas
authors.initials: N
authors.lastname: Gyllenstrand
authors.affiliation: Graduate School of Biostudies, Kyoto University, Kyoto, 606-8502, Japan.
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Nishihama
authors.affiliation: Department of Biology, Lund University, Ecology Building, SE-22362, Lund, Sweden.
authors.forename: Nils
authors.initials: N
authors.lastname: Cronberg
authors.affiliation: Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Muranaka
authors.affiliation: Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan.
authors.forename: Tokitaka
authors.initials: T
authors.lastname: Oyama
authors.affiliation: Graduate School of Biostudies, Kyoto University, Kyoto, 606-8502, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kohchi
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-75236, Uppsala, Sweden.|The Linnean Centre for Plant Biology in Uppsala, Uppsala, Sweden.
authors.forename: Ulf
authors.initials: U
authors.lastname: Lagercrantz
mesh_terms: D005075:Biological Evolution; D057906:Circadian Clocks / Q000235:genetics; D002940:Circadian Rhythm / Q000235:genetics; D019669:Embryophyta / Q000235:genetics / Q000502:physiology*; D035264:Flowers / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D017343:Genes, Plant; D017930:Genes, Reporter; D008156:Luciferases / Q000378:metabolism; D008163:Luminescent Measurements; D005810:Multigene Family; D009154:Mutation / Q000235:genetics; D010802:Phylogeny; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
chemical_list: D012333:RNA, Messenger; D008156:Luciferases
keywords: 
  Marchantia polymorpha
  ; bryophyte; circadian clock; evolution; transcription factor