Role of earthworm MTs in stress response and innate immunity

Metallothioneins (MTs) are proteins responsible for metal detoxification, radical scavenging, and play a role in immunity and infection. MTs occur throughout the animal kingdom in earthworms three isoforms have been identified, one of which is specifically detoxifying Cadmium (Cd). Cd is introduced into the environment through agriculture and industry and can cause, depending on exposure concentration and duration, various kinds of cellular damage. Cd-induced induction of MTs is therefore important to survive in contaminated environments. We observed that MT gene expression during Cd stress was suppressed when earthworms were wounded and therefore suggested that the stress response and immune reaction are linked on the molecular level. The present project aims at understanding how and why MTs are downregulated during wound healing. We hypothesize that limitations of essential trace elements and/or energy reserves could lead to a decrease in MT gene activity. We will furthermore investigate transcriptional regulators to reveal the molecular coordination of these cellular processes. Revealing if the earthworms immune cells underlie a so-called metabolic switch that drives the function towards either detoxification or immunity will further our understanding of the cellular part of the innate immune response. Taken together, we will gain detailed information how earthworms cope with stress like Cadmium exposure and injury with a focus on stress-induced MT regulation.