Induction of expression of a 14-3-3 gene in response to copper exposure in the marine alga, Fucus vesiculosus

Abstract

The macro-alga Fucus vesiculosus has a broad global and estuarine distribution and exhibits exceptional resistance to toxic metals, the molecular basis of which is poorly understood. To address this issue a cDNA library was constructed from an environmental isolate of F. vesiculosus growing in an area with chronic copper pollution. Characterisation of this library led to the identification of a cDNA encoding a protein known to be synthesised in response to toxicity, a full length 14-3-3 exhibiting a 71% identity to human/mouse epsilon isoform, 70-71% identity to yeast BMH1/2 and 95 and 71% identity to the Ectocarpus siliculosus 14-3-3 isoforms 1 and 2 respectively. Preliminary characterisation of the expression profile of the 14-3-3 indicated concentration- and time-dependent inductions on acute exposure of F. vesiculosus of copper (3-30 μg/l). Higher concentrations of copper (≥150 μg/l) did not elicit significant induction of the 14-3-3 gene compared with the control even though levels of both intracellular copper and the expression of a cytosolic metal chaperone, metallothionein, continued to rise. Analysis of gene expression within environmental isolates demonstrated up-regulation of the 14-3-3 gene associated with the known copper pollution gradient. Here we report for the first time, identification of a gene encoding a putative 14-3-3 protein in a multicellular alga and provide preliminary evidence to link the induction of this 14-3-3 gene to copper exposure in this alga. Interestingly, the threshold exposure profile may be associated with a decrease in the organism's ability to control copper influx so that it perceives copper as a toxic response.

Herbivore-induced defence response in the brown seaweedFucus vesiculosus(Phaeophyceae): temporal pattern and gene expression

“…Several genomic studies have provided insight into internal regulative processes in seaweeds, but these investigations were mainly focused on genes involved in carbohydrate synthesis (e.g. Zhou & Ragan, 1995), resistance to toxic metals (Owen et al, 2012) or epiphytes (Weinberger et al, 2011a) and acclimation to abiotic stresses (Dittami et al, 2009;Pearson et al, 2010;Heinrich et al, 2012b) (but see Cosse et al, 2009;de Oliveira et al, 2012). In contrast, cellular processes underlying the induction of anti-herbivory defences have been studied in detail for vascular plants.…”

Metal Accumulation and Metallothionein Response in Fucus spiralis

“…The MT gene has been identified in bladder wrack (Fucus vesiculosus) by Morris et al [24], which suggested that a protective mechanism against metal exposure exists for this species. Further studies suggest induction in this species following Cu exposure [9], as well as an ability to bind to As, Cd, and Zn [25,26]. This shows potential for MT to be developed as a biomarker in brown seaweeds.…”

“…Further studies confirmed its role as a detoxification mechanism for metals, and reported MT binding abilities to Zn, and As [25,26]. However, only Owen, et al [9] confirmed this role in the field in vivo. The study found MT to respond to Cu exposure, and this metal was found to be more important for MT induction, due to a stronger and more significant regression coefficient, compared to Zn and Fe.…”

“…Previous studies have not reported MT induction in Fucus spp. following exposure from these metals, with the exception of Fe [9]. However, these metals are known to induce MT in other species [53,54].…”

“…They have an ability to accumulate dissolved metals from seawater so their intracellular concentrations reflect time-integrated pollution loads in the marine environment [8]. As a consequence, seaweeds are established sentinels for metal contamination and are exploited for biomonitoring [9].…”