Persistent virus integration into the genome of its algal host, Ectocarpussiliculosus (Phaeophyceae)

The brown alga Ectocarpus siliculosus frequently carries an endogenous viru s, E, siliculosus virus (EsV-1), the genome of which is a circular, doubles tranded DNA molecule of about 320 kbp, After infection, which occurs in the unicellular spores or gametes, the virus is present latently in all somati c cells of the host. Virus multiplication is restricted to cells of the rep roductive organs. It has been an open question whether the latent viral DNA occurs as a free episome or becomes integrated into the host genome. PCR s tudies showed that viral DNA co-migrates with high molecular mass DNA in pu lsed-field gel electrophoresis, which confirms that latent viral DNA is int egrated into the host genome.