Protoporphyrinogen oxidase having an activity of imparting acifluorfen
resistance and gene thereof are provided. Cyanobacterium
protoporphyrinogen oxidase gene is identified by introducing a
protoporphyrinogen oxidase gene of Arabidopsis into cyanobacterium,
disrupting a cyanobacterium gene with a transposon, selecting a mutant
strain in which protoporphyrinogen oxidase gene is disrupted, identifying
the disrupted protoporphyrinogen oxidase gene, and isolating the
disrupted protoporphyrinogen oxidase gene. This procedure is effective as
a gene isolation technique when a protein derived from other organism
species that is homologous to a known protein (e.g., protoporphyrinogen
oxidase from cyanobacterium) can not be found in a gene database of the
other species.