Abstract
Photoperiodic flowering is a major factor determining crop performance and is controlled by interactions between environmental signals and the circadian clock. We proposed Hvlux1, an ortholog of the Arabidopsis circadian gene LUX ARRHYTHMO, as a candidate underlying the early maturity 10 (eam10) locus in barley (Hordeum vulgare L.).The link between eam10 and Hvlux1 was discovered using high-throughput sequencing of enriched libraries and segregation analysis. We conducted functional, phylogenetic, and diversity studies of eam10 and HvLUX1 to understand the genetic control of photoperiod response in barley and to characterize the evolution of LUX-like genes within barley and across monocots and eudicots.We demonstrate that eam10 causes circadian defects and interacts with the photoperiod response gene Ppd-H1 to accelerate flowering under long and short days. The results of phylogenetic and diversity analyses indicate that HvLUX1 was under purifying selection, duplicated at the base of the grass clade, and diverged independently of LUX-like genes in other plant lineages.Taken together, these findings contribute to improved understanding of the barley circadian clock, its interaction with the photoperiod pathway, and evolution of circadian systems in barley and across monocots and eudicots.
Highlights
Barley (Hordeum vulgare L.) is an important crop cultivated in a wide range of environments and has recently emerged as a model species for Triticeae as a result of its diploid nature and abundance of genomic resources (International Barley Sequencing Consortium (IBSC), 2012)
We present the characterization of the barley eam10 mutation, which causes an early-flowering phenotype under both short days (SDs) and long days (LDs). eam10 was described as an X-ray-induced mutation in Super Precoz (2H) of unknown parentage (Favret & Ryan, 1966; Gallagher et al, 1991; Gallagher & Franckowiak, 1997) and was mapped onto chromosome 3HL (B€orner et al, 2002)
We demonstrated that eam10 caused circadian defects and interacted with the major barley photoperiod response gene photoperiod response PHOTOPERIOD 1 gene (Ppd-H1) to accelerate flowering under LD and SD conditions
Summary
Barley (Hordeum vulgare L.) is an important crop cultivated in a wide range of environments and has recently emerged as a model species for Triticeae as a result of its diploid nature and abundance of genomic resources (International Barley Sequencing Consortium (IBSC), 2012). The dominant allele of Ppd-H1 is prevalent in the wild barley progenitor H. vulgare spp. spontaneum and in Mediterranean cultivated barley genotypes and accelerates flowering under LDs, as an adaptation to short growing seasons. A natural mutation in the conserved CCT domain of Ppd-H1 causes a reduced response to LDs and was selected for adaptation to long growing seasons (Turner et al, 2005; von Korff et al, 2006, 2010; Jones et al, 2008; Wang et al, 2010). Delayed flowering in genotypes with a mutated ppd-H1 allele was associated with reduced expression of HvFT1 (Turner et al, 2005; Campoli et al, 2012a)
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