Expression of a chitinase gene and lysis of the host cell wall during Chlorella virus CVK2 infection

A chitinase gene (vChti-1) encoded by the Chlorella virus CVK2 was cloned a nd characterized. The vChti-1 open reading frame consisted of 2508 bp corre sponding to 836 amino acid residues. The predicted amino acid sequence cont ained two sets of a family 18 catalytic domain that is responsible for chit inase activity. Northern blot analysis revealed that the vChti-1 gene was e xpressed in virus-infected Chlorella cells late in infection, when a single transcript of about 2.5 kb appeared at 120 min postinfection. This result was confirmed by Western blotting with a specific anti-vChti-1 protein anti body; a protein of about 94 kDa was detected specifically beginning at 240 min postinfection and was present until cell lysis. The protein was not inc orporated into viral particles but remained in the medium after cell lysis. The vChti-1 protein produced in virus-infected cells showed chitinase acti vity on zymogram assays. (C) 1999 Academic Press.