title: Diatom Phytochromes Reveal the Existence of Far-Red-Light-Based Sensing in the Ocean.
abstract: The absorption of visible light in aquatic environments has led to the common assumption that aquatic organisms sense and adapt to penetrative blue/green light wavelengths but show little or no response to the more attenuated red/far-red wavelengths. Here, we show that two marine diatom species, Phaeodactylum tricornutum and Thalassiosira pseudonana, possess a bona fide red/far-red light sensing phytochrome (DPH) that uses biliverdin as a chromophore and displays accentuated red-shifted absorbance peaks compared with other characterized plant and algal phytochromes. Exposure to both red and far-red light causes changes in gene expression in P. tricornutum, and the responses to far-red light disappear in DPH knockout cells, demonstrating that P. tricornutum DPH mediates far-red light signaling. The identification of DPH genes in diverse diatom species widely distributed along the water column further emphasizes the ecological significance of far-red light sensing, raising questions about the sources of far-red light. Our analyses indicate that, although far-red wavelengths from sunlight are only detectable at the ocean surface, chlorophyll fluorescence and Raman scattering can generate red/far-red photons in deeper layers. This study opens up novel perspectives on phytochrome-mediated far-red light signaling in the ocean and on the light sensing and adaptive capabilities of marine phototrophs.
authors.affiliation: Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, CNRS, Laboratoire de Biologie Computationnelle et Quantitative UMR 7238, 75006 Paris, France.
authors.forename: Antonio Emidio
authors.identifier: http://orcid.org/0000-0002-3173-5742
authors.initials: AE
authors.lastname: Fortunato
authors.affiliation: Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, CNRS, Laboratoire de Biologie Computationnelle et Quantitative UMR 7238, 75006 Paris, France.
authors.forename: Marianne
authors.identifier: http://orcid.org/0000-0001-5419-5796
authors.initials: M
authors.lastname: Jaubert
authors.affiliation: Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo 153-8902, Japan.
authors.forename: Gen
authors.initials: G
authors.lastname: Enomoto
authors.affiliation: Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, CNRS, Laboratoire de Biologie Computationnelle et Quantitative UMR 7238, 75006 Paris, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Bouly
authors.affiliation: Stazione Zoologica Anton Dohrn, 80121 Naples, Italy.
authors.forename: Raffaella
authors.identifier: http://orcid.org/0000-0002-3680-2043
authors.initials: R
authors.lastname: Raniello
authors.affiliation: Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, CNRS, Laboratoire de Biologie Computationnelle et Quantitative UMR 7238, 75006 Paris, France.
authors.forename: Michael
authors.initials: M
authors.lastname: Thaler
authors.affiliation: Ecole Normale Supérieure, PSL Research University, Institut de Biologie de l'Ecole Normale Supérieure, CNRS UMR 8197, INSERM U1024, F-75005 Paris, France.
authors.forename: Shruti
authors.initials: S
authors.lastname: Malviya
authors.affiliation: Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, CNRS, Laboratoire de Biologie Computationnelle et Quantitative UMR 7238, 75006 Paris, France.
authors.forename: Juliana Silva
authors.initials: JS
authors.lastname: Bernardes
authors.affiliation: Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 75005 Paris, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Rappaport
authors.affiliation: Sorbonne Universités, UPMC Univ-Paris 6, CNRS, UMR 7093, Laboratoire d'Océanologie de Villefranche, F-06230 Villefranche/mer, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Gentili
authors.affiliation: Protistology and Aquatic Ecology, Department of Biology, Ghent University, B-9000 Gent, Belgium Department of Plant Systems Biology, VIB, B-9052 Gent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, B-9052 Gent, Belgium.
authors.forename: Marie J J
authors.initials: MJ
authors.lastname: Huysman
authors.affiliation: Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, CNRS, Laboratoire de Biologie Computationnelle et Quantitative UMR 7238, 75006 Paris, France Institut Universitaire de France, 75005 Paris, France.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Carbone
authors.affiliation: Ecole Normale Supérieure, PSL Research University, Institut de Biologie de l'Ecole Normale Supérieure, CNRS UMR 8197, INSERM U1024, F-75005 Paris, France.
authors.forename: Chris
authors.initials: C
authors.lastname: Bowler
authors.affiliation: Stazione Zoologica Anton Dohrn, 80121 Naples, Italy maurizio@szn.it angela.falciatore@upmc.fr.
authors.forename: Maurizio Ribera
authors.identifier: http://orcid.org/0000-0002-5492-9961
authors.initials: MR
authors.lastname: d'Alcalà
authors.affiliation: Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo 153-8902, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Ikeuchi
authors.affiliation: Sorbonne Universités, UPMC, Institut de Biologie Paris-Seine, CNRS, Laboratoire de Biologie Computationnelle et Quantitative UMR 7238, 75006 Paris, France maurizio@szn.it angela.falciatore@upmc.fr.
authors.forename: Angela
authors.initials: A
authors.lastname: Falciatore
mesh_terms: D000222:Adaptation, Physiological; D002734:Chlorophyll / Q000378:metabolism; D017377:Diatoms / Q000502:physiology* / Q000528:radiation effects; D055537:Light Signal Transduction / Q000528:radiation effects*; D009792:Oceans and Seas; D010834:Phytochrome / Q000528:radiation effects*; D010944:Plants / Q000528:radiation effects*; D013059:Spectrum Analysis, Raman; D013472:Sunlight
chemical_list: D010834:Phytochrome; D002734:Chlorophyll