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Genes Dev. 2018 Oct 1;32(19-20):1332-1343. doi: 10.1101/gad.318592.118. Epub 2018 Sep 25.

Arabidopsis RUP2 represses UVR8-mediated flowering in noninductive photoperiods.

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Department of Botany and Plant Biology, Section of Biology, Faculty of Sciences, University of Geneva, 1211 Geneva 4, Switzerland.
Department of Plant Physiology, Center for Plant Molecular Biology (ZMBP), University of Tübingen, 72076 Tübingen, Germany.
Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland.
Research Unit Environmental Simulation, Helmholtz Zentrum München, 85764 Neuherberg, Germany.
Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 1211 Geneva 4, Switzerland.


Plants have evolved complex photoreceptor-controlled mechanisms to sense and respond to seasonal changes in day length. This ability allows plants to optimally time the transition from vegetative growth to flowering. UV-B is an important part intrinsic to sunlight; however, whether and how it affects photoperiodic flowering has remained elusive. Here, we report that, in the presence of UV-B, genetic mutation of REPRESSOR OF UV-B PHOTOMORPHOGENESIS 2 (RUP2) renders the facultative long day plant Arabidopsis thaliana a day-neutral plant and that this phenotype is dependent on the UV RESISTANCE LOCUS 8 (UVR8) UV-B photoreceptor. We provide evidence that the floral repression activity of RUP2 involves direct interaction with CONSTANS, repression of this key activator of flowering, and suppression of FLOWERING LOCUS T transcription. RUP2 therefore functions as an essential repressor of UVR8-mediated induction of flowering under noninductive short day conditions and thus provides a crucial mechanism of photoperiodic flowering control.


Arabidopsis; UV-B photoreceptor; UVR8; flowering; photoperiodism; plant–environment interaction; sun simulator

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