Mutation to Herbicide Resistance Maps Within the psbA Gene of Anacystis nidulans R2

A psbA gene encoding the target of photosystem II herbicide inhibition, the 32,000-dalton thylakoid membrane protein, has been cloned from a mutant of Anacystis nidulans R2, which is resistant to 3-(3,4-dichlorophenyl)-1,1-dimethylurea-(diuron). A cloned DNA fragment from within the coding region of this gene transforms wild-type cells to herbicide resistance, proving that mutation within psbA is responsible for that phenotype. The mutation consists of a single nucleotide change that replaces serine at position 264 of the wild-type protein with alanine in that of the diuron-resistant mutant.