Constitutive or Inducible Protective Mechanisms against UV-B Radiation in the Brown Alga Fucus vesiculosus? A Study of Gene Expression and Phlorotannin Content Responses
|Author(s)||Creis Emeline1, Delage Ludovic1, Charton Sophie1, Goulitquer Sophie2, Leblanc Catherine1, Potin Philippe1, Gall Erwan Ar3|
|Affiliation(s)||1 : Univ Paris 06, Sorbonne Univ, CNRS,CS 90074, UMR Integrat Biol Marine Models 8227,Stn Biol Ros, F-29688 Roscoff, France.
2 : CNRS, Ctr Ressources Biol Marine, MetaboMer Mass Spectrometry Core Facil, Stn Biol Roscoff,FR2424, F-29688 Roscoff, Brittany, France.
3 : Univ Bretagne Occidentale, Univ Europeenne Bretagne, CNRS 6539,Unite Mixte Rech, Inst Europeen Etud Marines IUEM,Lab Sci Environm, F-29280 Plouzane, Brittany, France.
|Source||Plos One (1932-6203) (Public Library Science), 2015-06 , Vol. 10 , N. 6 , P. -|
|WOS© Times Cited||9|
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.