Induction of Phlorotannins and Gene Expression in the Brown Macroalga Fucus vesiculosus in Response to the Herbivore Littorina littorea

Mechanisms related to the induction of phlorotannin biosynthesis in marine brown algae remain poorly known. Several studies undertaken on fucoid species have shown that phlorotannins accumulate in the algae for several days or weeks after being exposed to grazing, and this is measured by direct quantification of soluble phenolic compounds. In order to investigate earlier inducible responses involved in phlorotannin metabolism, Fucus vesiculosus was studied between 6 and 72 h of grazing by the sea snail Littorina littorea. In this study, the quantification of soluble phenolic compounds was complemented by a Quantitative real-time PCR (qRT-PCR) approach applied on genes that are potentially involved in either the phlorotannin metabolism or stress responses. Soluble phlorotannin levels remained stable during the kinetics and increased significantly only after 12 h in the presence of grazers, compared to the control, before decreasing to the initial steady state for the rest of the kinetics. Under grazing conditions, the expression of vbpo, cyp450 and ast6 genes was upregulated, respectively, at 6 h, 12 h and 24 h, and cyp450 gene was downregulated after 72 h. Interestingly, the pksIII gene involved in the synthesis of phloroglucinol was overexpressed under grazing conditions after 24 h and 72 h. This study supports the hypothesis that phlorotannins are able to provide an inducible chemical defense under grazing activity, which is regulated at different stages of the stress response

Diversité des peuplements de macroalgues de Bretagne

National audienc

Antiallergic properties

International audienceA brief introduction gives the state of the art concerning allergies related to the consumption of seafoods. In this type of product, allergenic substances are mainly muscle proteins and thus largely concern fish, shellfish, mollusks, and crustaceans. The literature available regarding food intolerance caused by eating seaweeds is very restricted. Paradoxically, many works have been carried out on the antiallergic properties of macroalgae. This chapter deals with the species shown to be active against allergies and the specific compounds involved, including phenols, in particular phlorotannins in Phaeophyceae, and polysaccharides, such as alginates and porphyrans. Perspectives for using some seaweeds in the development of functional foods are discussed. The harmlessness of most edible seaweeds is also mentioned

Intercalibration de l'indicateur "macroalgues intertidales" : Mission Asturies-Eaux de transition - Rapport final - Convention 2010 - Action 5

La mission "Asturies" - MET du Lébham s’est déroulée du 13 juin au 18 juin 2010. Le but de cette mission était double. Il s’agissait d’une part de prendre connaissance des techniques utilisées en Asturies pour suivre l’élément macroalgues dans les eaux de transition, et, d’autre part, de voir si le protocole en développement sur les estuaires bretons était transposable aux estuaires asturiens. Cette mission s’est malheureusement déroulée pendant un fort épisode d’inondations qui a perturbé la partie terrain, l’accès à certains secteurs d’étude étant impossible

Première observation de l’algue rouge Centroceras clavulatum (Agardh) Montagne dans les eaux bretonnes et plus largement sur les côtes nord-européennes

International audienceUne espèce d’algue rouge,Centroceras clavulatum(Agardh) Montagne est décrite pour la première fois dans le golfe du Morbihan. Plus largement, il s’agit de la première observation de cette espèce sur les côtes nord-européennes

The microbiome of Codium tomentosum: original state and in the presence of copper

WOS:000492408400001International audienceCodium tomentosum, as all organisms, hosts transiently and permanently numerous microorganisms. These holobionts can undergo environmental pressures influencing both partners creating modifications/imbalances within the associations, which may directly influence their physiological status by selecting tolerant bacteria. Furthermore, the capability of remediation of the associated bacterioflora, in particular of metallic trace elements, may provide the host with survival potential in polluted environments. In this context, we incubated C. tomentosum thalli in the presence of copper and studied its influence on the reference bacteriome. Whatever the concentration of copper, no shift was evidenced on the bacteriome at the phylum level. However, a high copper concentration enriched the bacteriome of C. tomentosum in both the genera Clostridium and Pseudolteromonas

Development of a quality index to evaluate the structure of macroalgal communities

International audienceA quality index Ics (= index of community structure) has been developed as a single numeric descriptor to assess the structural state of macroalgal communities and to evaluate their relative development on rocky shores. Coverage of seaweed species were sampled on the field and treated by taxonomic groups, size classes and structural - functional groups (SFG), giving sub-indices It (= taxonomic index), Is (= stratification index) and Io (= organization index), respectively. Six macroalgal communities corresponding to canopies (belts) distributed vertically on the shore have been investigated for several years in 14 sites of Brittany (France). Communities developing at high topographic levels could be distinguished from those occurring at mid-tide to low levels by la values. Communities were globally stable over the sampling period, with few geographical discrepancies. Seasonal or sub-community variations could be tracked by sub-index values. The value of Ics to demonstrate the potential evolution of seaweed communities is discussed by comparison to other quality indices and in the perspective of ecological perturbations

Radiations UV et composés photoprotecteurs (étude comparée chez deux végétaux marins, l'algue brune Pelvetia canaliculata et l'angiosperme Salicornia ramosissima)

Les fortes intensités lumineuses, et notamment l augmentation actuelle de l intensité des radiations UV-B due à l amincissement de la couche d ozone, peuvent être des facteurs stressants majeurs pour la plupart des organismes phototrophes peuplant les écosystèmes terrestres et aquatiques. L algue brune Pelvetia canaliculata et l angiosperme des marais salés littoraux Salicornia ramosissima sont deux végétaux marins peuplant les hauts niveaux de l estran, zone où ils sont soumis à de longues périodes d exondation, exposés de manière directe au rayonnement solaire et susceptibles de posséder des mécanismes de photoprotection convergents efficaces. Dans cette étude, grâce à la mise au point d un système de co-culture, leurs réponses métaboliques contre l exposition â différentes niveaux de radiations UV-B ont été comparées en conditions contrôlées, notamment la synthèse de composés photoprotecteurs impliqués dans le maintien de la photosynthèse par la filtration des radiations UV et la défense contre le stress oxydatif. Les résultats montrent que les composés phénoliques semblent être la classe majoritaire de composés photoprotecteurs impliquée chez les deux espèces, avec un rôle écran préférentiel des flavonoïdes chez Salicornia ramosissima et une forte activité antioxydante des phlorotannins chez Pelvetia canaliculata. Cependant, les deux espèces pourraient moduler la composition de leur pool de composés phénoliques en jouant sur une de ces activités protectrices ou sur les deux, en fonction des conditions lumineuses. La fonction spécifique de filtration des radiations UV des composés photoprotecteurs a été mise en évidence après le développement d une nouvelle méthode de mesure in vitro de l activité écran d extraits végétaux.High light irradiances, especially enhanced UV-B radiations due to present stratospheric ozone depletion, may be major stress factors for many phototrophic organisms in both aquatic and terrestrial ecosystems. The brown seaweed Pelvetia canaliculata and the coastal salt marsh angiosperm Salicornia ramosissima are two marine plants growing in the upper intertidal zone, where they are subjected to long emersion periods, to direct solar exposure and are likely to have convergent efficient photoprotective mechanisms. In this study, thanks to the development of a coculture system, their metabolic responses against various UV-B radiation levels have been compared in controlled conditions, especially the synthesis of photoprotective compounds implied in the photosynthesis maintaining by either a UV-absorbing function or a defence capacity against oxidative stress. Results show that phenols seem to be the main class of photoprotective compounds in both species, with a preferential sunscreen function of flavonoids in Salicornia ramosissima and a strong antioxidant activity of phlorotannins in Pelvetia canaliculata. However, both species could modulate the composition of their phenol pool through either 011e protective function or both depending on light conditions. The specific UV-absorbing function of these compounds has been evidenced thanks to the development of a new in vitro method for evaluating the sunscreen activity of plant extracts.BREST-BU Droit-Sciences-Sports (290192103) / SudocPLOUZANE-Bibl.La Pérouse (290195209) / SudocSudocFranceF

Influence of day-night and tidal cycles on phenol content and antioxidant capacity in three temperate intertidal brown seaweeds

International audienceThe daily variations of phenol contents and antioxidant capacities were surveyed in a 32-h field experiment in three temperate brown seaweeds belonging to Fucales - Pelvetia canaliculata, Ascophyllum nodosum and Bifurcaria bifurcata - living at different intertidal levels -- high-, mid- and low-tide level, respectively. Phenolic compounds of brown seaweeds are secondary metabolites involved in many different protection mechanisms, as for example against grazer and pathogen attack as well as UV damage. This study was thus aimed at understanding the influence of both day/night and tidal cycles on the brown seaweed phenol pool with respect to their bathymetric level on the shore. These cycles affect the quantity and quality of light received by intertidal seaweeds (protection via the water layer during immersion), and the photoprotective role of phlorotannins was thus evaluated. Phenol levels and antioxidant capacities were monitored every hour during a tidal cycle and a half at the equinox spring tide, in March 2003. The three species contained rather high phenol levels, i.e. about 3, 6 and 4% DW in P. canaliculata, A. nodosum and B. bifurcata, respectively. Antioxidant capacities globally paralleled phenol contents in the three species under study. Moreover, the measured antioxidant capacities and the phenol contents of the extracts were significantly and positively correlated in the three species. Significant effect of neither cycles nor their interaction was observed in any species despite a trend to follow day/night alternation for P. canaliculata, and emersion/immersion cycle for A. nodosum. No trend was observed for the third species. However, significant correlations between phenol levels of P. canaliculata and A. nodosum and measured air-temperature were found. Our results suggested an effect of aerial, aquatic and both conditions on the phenolic pool of P. canaliculata, B. bifurcata and A. nodosum, respectively, and a fast evolution of the phenolic pool on a day time scale