A field study of the molecular response of brown macroalgae to heavy metal exposure: an (epi)genetic approach

Our understanding of the relative contribution of genetic and epigenetic mechanisms to organismal response to stress is largely biased towards specific taxonomic groups (e.g. seed plants) and environmental stresses (e.g., drought, salinity). In previous work, we found intraspecific differences in heavy metal (HM) uptake capacity in the brown macroalgae Fucus vesiculosus. The molecular mechanisms underlying these differences, however, remained unknown. Here, we determined the concentrations of HMs, and characterized the genetic (single nucleotide polymorphisms) and epigenetic (cytosine DNA methylation) variability in reciprocal transplants of F. vesiculosus between two polluted and two unpolluted sites on the NW Spanish coast after 90 days. Genetic and epigenetic differentiation did not explain the phenotypic differentiation observed, possibly due to the combined effect of multiple environmental factors acting on the algae in their natural habitats. Nonetheless, we provide further evidence of intraspecific genetic differentiation in F. vesiculosus at short spatial scales, as well as first evidence of population-specific epigenetic changes in brown macroalgae in response to changes in environmental conditions (i.e. transplantation ex situ). We propose that both genetic and, to some extent, epigenetic mechanisms might impinge upon the adaptive potential of this species to environmental change, but this needs to be further addressed.