title: Mutation at the circadian clock gene EARLY MATURITY 8 adapts domesticated barley (Hordeum vulgare) to short growing seasons.
abstract: The circadian clock is an autonomous oscillator that produces endogenous biological rhythms with a period of about 24 h. This clock allows organisms to coordinate their metabolism and development with predicted daily and seasonal changes of the environment. In plants, circadian rhythms contribute to both evolutionary fitness and agricultural productivity. Nevertheless, we show that commercial barley varieties bred for short growing seasons by use of early maturity 8 (eam8) mutations, also termed mat-a, are severely compromised in clock gene expression and clock outputs. We identified EAM8 as a barley ortholog of the Arabidopsis thaliana circadian clock regulator EARLY FLOWERING3 (ELF3) and demonstrate that eam8 accelerates the transition from vegetative to reproductive growth and inflorescence development. We propose that eam8 was selected as barley cultivation moved to high-latitude short-season environments in Europe because it allowed rapid flowering in genetic backgrounds that contained a previously selected late-flowering mutation of the photoperiod response gene Ppd-H1. We show that eam8 mutants have increased expression of the floral activator HvFT1, which is independent of allelic variation at Ppd-H1. The selection of independent eam8 mutations shows that this strategy facilitates short growth-season adaptation and expansion of the geographic range of barley, despite the pronounced clock defect.
authors.affiliation: Crop Genetics Department,  John Innes Centre, Norwich NR4 7UH,  United Kingdom.
authors.forename: Sebastien
authors.initials: S
authors.lastname: Faure
authors.forename: Adrian S
authors.initials: AS
authors.lastname: Turner
authors.forename: Damian
authors.initials: D
authors.lastname: Gruszka
authors.forename: Vangelis
authors.initials: V
authors.lastname: Christodoulou
authors.forename: Seth J
authors.initials: SJ
authors.lastname: Davis
authors.forename: Maria
authors.initials: M
authors.lastname: von Korff
authors.forename: David A
authors.initials: DA
authors.lastname: Laurie
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics; D061146:Chlorophyll Binding Proteins / Q000235:genetics; D002940:Circadian Rhythm / Q000235:genetics*; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D035264:Flowers / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D001467:Hordeum / Q000235:genetics* / Q000254:growth & development* / Q000502:physiology; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000502:physiology; D010641:Phenotype; D017440:Photoperiod; D012621:Seasons; D014157:Transcription Factors / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D061146:Chlorophyll Binding Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; D014157:Transcription Factors; C432430:At2g25930 protein, Arabidopsis