Algal-lytic activities encoded by Chlorella virus CVK2

Using a halo assay with E. coli lysates expressing Chlorella virus CVK2 gen es on a cosmid contig, two different algal-lytic activities against Chlorel la 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 homo logous to PBCV-1 A215L and CVN1 CL-2. The vAL-1 gene was expressed at relat ively early stages of the virus life cycle; transcripts and translation pro ducts appeared at 60 and 90 min postinfection, respectively. The vAL-1 prot ein 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 re lease at the final stage of infection. Cell wall materials isolated from Ch lorella strain NC64A cells were digested by vAL-1 and degradation products were detected on TLC. In addition to Chlorella strain NC64A, vAL-1 lysed ce lls of four C. vulgaris strains as well as Chlorella sp. SAG-241-80. (C) 20 00 Academic Press.