Metal influence on metallothionein synthesis in the hydrothermal vent mussel Bathymodiolus thermophilus

The present study reports on the metallothionein expression in the hydrothermal vent mussel Bathymodiolus thermophilus. Metal lothioneins (MT) are proteins involved in intracellular metal regulation and conserved throughout the animal kingdom. The hydrothermal vent environment presents peculiarities (high levels of sulfides and metals, low pH, anoxia) that may have driven associated species to develop original evolutionary ways to face these extreme living conditions. Mussels were exposed to different metal solutions at the atmospheric pressure. The MT mRNA levels and NIT contents were measured in gills and mantles of each exposed mussel. The intracellular metal distribution was estimated in fractions obtained after the centrifugation of tissue homogenates. A few of the tested metals (Ag, Cu, Cd, Hg and Zn) were able to significantly induce MT mRNA levels. Silver was the only one that produced a significant increase of the NIT protein level in both mantle and gills. The gills always presented higher NIT protein levels than the mantle did, while their MT mRNA levels were similar. Our data show that NIT mRNA and NIT protein levels do not follow a clear relationship in the gills and mantle of B. thermophilus and we assume that a posttranscriptional control occurs in these mussels. (c) 2006 Elsevier Inc. All rights reserved.