Positive selection vector using the KillerRed gene.

Plasmid pZK18S is a novel positive selection vector containing the genetically encoded photosensitizer KillerRed as the selection marker. When transformed into host cells (lacI(q) or lacI(+)), the common medical surgical light is sufficient to activate phototoxicity of KillerRed. Thus, only the recombinants with disrupted reading frame of KillerRed genes finally allow forming viable colonies. Because lethality of KillerRed relies on light irradiation, no special host and culture medium are required to amplify and prepare pZK18S vector in larger quantities. The pZK18S was reliable and highly efficient for constructing the serial analysis of gene expression (SAGE) library.