Evidences for antimicrobial peptides in the colonial ascidian Botryllus schlosseri

Invertebrates have acquired many mechanisms of defence in order to overwhelm the risk of pathogen attack. In particular, the presence of various types of antimicrobial peptides (AMP) guarantees an efficient response, making them able to kill both gram positive and negative bacteria, fungi and viruses. In ascidians, AMPs have been isolated and described in different species, such as in Styela clava (Clavanins and Styelins) and in Ciona intestinalis (the recent Ci-MAM). Previous studies have revealed molecules, including phenoloxidase and rhamnose-binding lectins, with an antimicrobial effect also in Botryllus schlosseri. Here, we report that the growth of some bacteria strains is highly inhibited by extracts of haemocytes, showing alterations in their surface. Moreover, molecular analyses allowed us to identify a Botryllus sequence similar to Styelins that is abundantly transcribed in phagocytes.