Earthworm and Nematode Metallothioneins
The earthworm and the nematode are primary soil sentinel and model invertebrate organisms. Their metallothioneins (MT) display striking structural and functional features. Firstly, the primary sequences, though remarkably conserved within species belonging to the same genus, have notable divergencies containing additional potentially metal-binding residues. Secondly, cadmium is the major transcriptional activator of MT expression in the intestinal cells. Thirdly, the MT promoters seemingly lack functional metal response elements which underlines the finding that MTF-1 is absent from the nematode and possibly the earthworm genome. This chapter highlights past, present, and future advances aiming to dissect the synergies and discrepancies of the metallothioneins from two evolutionary very distant relatives of soil dwelling worms.