Algal-lytic activities encoded by Chlorella virus CVK2

Using a halo assay with E. coli lysates expressing Chlorella virus CVK2 genes on a cosmid contig, two different algal-lytic activities against Chlorella strain NC64A cells were found to be encoded on the CVK2 genome. The gene for vAL-1, one of the two activities, encoded a 349-aa ORF, which was homologous to PBCV-1 A215L and CVN1 CL-2. The vAL-1 gene was expressed at relatively early stages of the virus life cycle; transcripts and translation products appeared at 60 and 90 min postinfection, respectively. The vAL-1 protein was not incorporated into the viral particles but remained in the cell lysate, suggesting a role in the digestion of the cell wall before viral release at the final stage of infection. Cell wall materials isolated from Chlorella strain NC64A cells were digested by vAL-1 and degradation products were detected on TLC. In addition to Chlorella strain NC64A, vAL-1 lysed cells of four C. vulgaris strains as well as Chlorella sp. SAG-241-80. (C) 2000 Academic Press.