title: CONSTANS Controls Floral Repression by Up-Regulating VERNALIZATION2 (VRN-H2) in Barley.
abstract: In barley (Hordeum vulgare), PHOTOPERIOD1 (Ppd-H1) acts as a major positive regulator of flowering under long-day conditions, while VERNALIZATION2 (VRN-H2) is a strong repressor of flowering under long days before vernalization. By contrast, CONSTANS (CO) plays a key role in the photoperiodic regulation of flowering in Arabidopsis (Arabidopsis thaliana). Here, we study the role of the closest barley CO homologs, HvCO1 and HvCO2, in the long day-dependent control of flowering and their interactions with Ppd-H1 and VRN-H2. HvCO2 overexpression in spring barley, with a natural deletion of the VRN-H2 locus, caused a Ppd-H1-dependent induction of flowering and FLOWERING LOCUS T1 (HvFT1) expression. In winter barley, which carries the VRN-H2 locus, overexpression of HvCO1/CO2 caused an up-regulation of VRN-H2, resulting in a reduced expression of HvFT1 and delayed flowering under long- and short-day conditions. In addition, natural variation at Ppd-H1 altered the expression of VRN-H2 in wild-type plants under long days. VRN-H2, in turn, was involved in the down-regulation of Ppd-H1 and HvCO2, demonstrating strong reciprocal interactions between HvCO2, Ppd-H1, and VRN-H2. Consequently, this study showed that the induction of the floral repressor VRN-H2 and the floral activator HvFT1 was regulated by the same genes, Ppd-H1 and HvCO1/CO2. Our findings provide a novel insight into the photoperiodic regulation of the vernalization pathway in barley.
authors.affiliation: Max Planck Institute for Plant Breeding Research, D-50829 Cologne, Germany (M.A.M., M.v.K.);Institute of Plant Genetics, Heinrich-Heine-University, 40225 Duesseldorf, Germany (M.A.M., M.v.K.); andCluster of Excellence on Plant Sciences, From Complex Traits towards Synthetic Modules, 40225 Duesseldorf, Germany (M.v.K.).
authors.forename: Muhammad Aman
authors.identifier: http://orcid.org/0000-0003-3511-537X
authors.initials: MA
authors.lastname: Mulki
authors.affiliation: Max Planck Institute for Plant Breeding Research, D-50829 Cologne, Germany (M.A.M., M.v.K.);Institute of Plant Genetics, Heinrich-Heine-University, 40225 Duesseldorf, Germany (M.A.M., M.v.K.); andCluster of Excellence on Plant Sciences, From Complex Traits towards Synthetic Modules, 40225 Duesseldorf, Germany (M.v.K.) korff@mpipz.mpg.de.
authors.forename: Maria
authors.identifier: http://orcid.org/0000-0002-6816-586X
authors.initials: M
authors.lastname: von Korff
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D035264:Flowers / Q000235:genetics / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D001467:Hordeum / Q000235:genetics / Q000502:physiology*; D017440:Photoperiod; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D014157:Transcription Factors / Q000235:genetics; D015854:Up-Regulation
chemical_list: D029681:Arabidopsis Proteins; C092776:CONSTANS protein, Arabidopsis; D004268:DNA-Binding Proteins; D010940:Plant Proteins; D014157:Transcription Factors