Characterisation of the coccolithovirus protein EHV298

Emiliania huxleyi virus (EhV) is associated with bloom termination of Emiliania huxleyi - the most abundant coccolithophore and one of the major primary producers in the oceans. This virus has a giant genome of approximately 400 kbp and between 470 and 510 predicted protein encoding sequences (CDSs), of which 80 % have no database homologs or known function. The virus gene ehv298 was found to be highly expressed shortly after infection and is located downstream of a putative promoter region. To date, EHV298 is the only EhV protein with a resolved crystal structure, which makes it an ideal candidate for investigation with regard to virus-host interaction. The diversity of the protein EHV298 was assessed by screening laboratory EhV strains and environmental samples for the ehv298 gene. To determine the prevalence of the protein on a broader scale, metagenomic databases from global oceanic cruises were searched for the EHV298 protein. Protein interaction was investigated by using DNA, RNA and protein from the host and the virus for pull down assays. Four different versions of the protein were identified between the isolated EhV strains, which were highly conserved at both the nucleotide and amino acid level. Three unknown ehv298 alleles were additionally amplified from the environmental samples. However conclusive genetic markers for EhV as well as ehv298 were absent from the global environmental databases. Therefore, all information to date on the Emiliania huxleyi virus is primarily based on strains from the North Atlantic. The global distribution of coccolithoviruses as well as that of ehv298 requires further investigation. Furthermore seven candidate binding proteins from E.huxleyi were identified, of which two are involved in the tricarboxylic acid cycle. Interaction between these proteins and EHV298 has yet to be confirmed.In collaboration with Plymouth Marine Laboratory (PML