Molecular analysis of the AHAS gene of Porphridium sp (Rhodophyta) and of a mutant resistant to sulfometuron methyl

Acetohydroxyacid synthase (AHAS) is the target enzyme of the sulfonylurea h erbicides, and here we report the sequence of the gene from wild-type and h erbicide-resistant Porphyridium sp, (Rhodophyta), The resistant mutant has a single residue substitution at a position known to confer herbicide resis tance in E. coli and in plants. The rhodophyte gene is of cyanobacterial or igin and distinct from the nuclear-encoded chlorophyte gene, which may be o f mitochondrial origin.