Plugge, B., Becker, B., Gradmann D. and Wolf, A.H.
Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Universität Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany
We have isolated and characterized the major coat protein Vp49 and its corresponding gene from German Chlorella virus isolate CVG-1 (Phycodnaviridae). Three more open reading frames were identified and sequenced, which showed significant sequence similarity with Vp49. CVG-1 represents the European Pbi-subgroup of the Phycodnaviridae and neither infects nor attaches to Chlorella host strains of other subgroups. As this distinct host specificity may be linked to differences in capsid composition, the sequences were compared to data from virus isolates PBCV1 and CVK2, representing the NC64A-subgroup of the family. The major coat proteins have a high degree of homology and are similar in size, but differ in glycosylation. CVG-1 ORF8 corresponds well to a PBCV-1 gene similar in size and sequence, while ORF3 shows only weak homology to other virus genes. A fourth, incomplete CVG-1 ORF has the same aminoterminus as the major coat protein Vp49. The variability in certain regions of the major coat protein sequences could account for the viruses´ host specificity. Moreover, they show that viruses of the different subgroups did evolve separately, probably parallel to their respective host algae.