title: Constitutive or Inducible Protective Mechanisms against UV-B Radiation in the Brown Alga Fucus vesiculosus? A Study of Gene Expression and Phlorotannin Content Responses.
abstract: A role as UV sunscreens has been suggested for phlorotannins, the phenolic compounds that accumulate in brown algae in response to a number of external stimuli and take part in cell wall structure. After exposure of the intertidal brown alga Fucus vesiculosus to artificial UV-B radiation, we examined its physiological responses by following the transcript level of the pksIII gene encoding a phloroglucinol synthase, likely to be involved in the first step of phlorotannins biosynthesis. We also monitored the expression of three targeted genes, encoding a heat shock protein (hsp70), which is involved in global stress responses, an aryl sulfotransferase (ast), which could be involved in the sulfation of phlorotannins, and a vanadium bromoperoxidase (vbpo), which can potentially participate in the scavenging of Reactive Oxygen Species (ROS) and in the cross-linking and condensation of phlorotannins. We investigated whether transcriptional regulation of these genes is correlated with an induction of phlorotannin accumulation by establishing metabolite profiling of purified fractions of low molecular weight phlorotannins. Our findings demonstrated that a high dose of UV-B radiation induced a significant overexpression of hsp70 after 12 and 24 hours following the exposure to the UV-B treatment, compared to control treatment. The physiological performance of algae quantified by the photosynthetic efficiency (Fv/Fm) was slightly reduced. However UV-B treatment did not induce the accumulation of soluble phlorotannins in F. vesiculosus during the kinetics of four weeks, a result that may be related to the lack of induction of the pksIII gene expression. Taken together these results suggest a constitutive accumulation of phlorotannins occurring during the development of F.vesiculosus, rather than inducible processes. Gene expression studies and phlorotannin profiling provide here complementary approaches to global quantifications currently used in studies of phenolic compounds in brown algae.
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff cedex, France.
authors.forename: Emeline
authors.initials: E
authors.lastname: Creis
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff cedex, France.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Delage
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff cedex, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Charton
authors.affiliation: Centre de Ressources de Biologie Marine, MetaboMer Mass Spectrometry Core Facility, CNRS FR2424, Station Biologique de Roscoff, 29688, Roscoff cedex, Brittany, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Goulitquer
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff cedex, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Leblanc
authors.affiliation: Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff cedex, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Potin
authors.affiliation: Université Européenne de Bretagne, Université de Bretagne Occidentale, Laboratoire des Sciences de l'Environnement Marin, Unité Mixte de Recherche, Centre National de la Recherche Scientifique 6539, Institut Européen d'Etudes Marines-IUEM, 29280, Plouzané, Brittany, France.
authors.forename: Erwan
authors.initials: E
authors.lastname: Ar Gall
mesh_terms: D044645:Fucus / Q000235:genetics / Q000378:metabolism* / Q000502:physiology / Q000528:radiation effects*; D008970:Molecular Weight; D010696:Phloroglucinol / Q000737:chemistry / Q000378:metabolism*; D059467:Transcriptome / Q000528:radiation effects*; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D010696:Phloroglucinol