Characterization of two chitinase genes and one chitosanase gene encoded by chlorella virus PBCV-1

Chlorella virus PBCV-1 encodes two putative chitinase genes, a181/182r and a260r, and one chitosanase gene, a292l. The three genes were cloned and exp ressed in Escherichia coli. The recombinant A181/182R protein has endochiti nase activity, recombinant A260R has both endochitinase and exochitinase ac tivities, and recombinant A292L has chitosanase activity. Transcription of a181/182r, a260r, and a 292l genes begins at 30, 60, and 60 min p.i., respe ctively; transcription of all three genes continues until the cells lyse. A 181/182R, A260R, and A292L protein are first detected by Western blots at 6 0, 90, and 120 min p.i., respectively. Therefore, a181/182r is an early gen e and a260r and a292l are late genes. All three genes are widespread in chl orella viruses. Phylogenetic analyses indicate that the ancestral condition of the a181/182r gene arose from the most recent common ancestor of a gene found in tobacco, whereas the genealogical position of the a260r gene coul d not be unambiguously resolved. (C) 1999 Academic Press.