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

Abstract

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.

Phlorotannins of the Brown Algae Sargassum vulgare from the Mediterranean Sea Coast

“…Indeed, such compounds have been previously described in other species, such as Pleurophycus gardneri [ 66 ] and A. nodosum [ 65 ]. Moreover, according to Emeline et al [ 67 ], in Littorina littorea , upon the commencement of grazing activity, a significant increase in the gene expression of aryl sulfotransferase, an enzyme known to be involved in the sulfation of various compounds (including phenols), was observed in F. vesiculosus , which could be responsible for the sulfation of phlorotannins as part of its anti-grazing defense mechanism.…”

Marine natural products

“…A study of the temporal effects of herbivore (sea snail Littorina littorea) predation upon Fucus vesiculosus has shown that tannins have a role as an inducible chemical defence upon grazing by the snails, and that grazing has differential temporal effects upon the stress response of the alga. 390 5 Red algae A Japanese Laurencia yielded two new C 15 acetogenins 936 and 937, 391 while a Soliera was the source of new aromatic polyketide 938. 392 An ethanolic extract of a Chinese L. tristicha was the source of 4-isopropylbenzaldehyde-containing products, presumably formed by condensation with acetophenone, as exemplied by 939.…”

Aquatic Phlorotannins and Human Health: Bioavailability, Toxicity, and Future Prospects

“…Summarily, oxidative stress, herbivory activities, and UV-radiation are the central reported stimulants for phlorotannin secondary metabolite production. 57…”

“…Studies have implicated phlorotannins as an inducible metabolite, overproduced as an outcome of stress in several species of brown algae. 57,58 There is potential for some phlorotannins to act as insecticides based on their structural–function inference, although there are no studies at the time of this review to validate claims. Other bioactive roles from recent literature have shown phlorotannins to possess antioxidant, antimicrobial, anti-inflammatory, antiproliferative, antitumor, antidiabetic, radio-protective anti-adipogenic, and anti-allergic activities.…”

“…A few studies have shown that phlorotannins are inducible secondary metabolites induced by herbivory activities. 57 Stern et al 72 reported that phlorotannins act as an antifeedant as they form a covalent bond with the gut proteins of herbivores. Similarly, another study conducted by Koivikko et al 58 discovered increased phlorotannin content with increased herbivory activities.…”