Abstract
Transformation of fungi by complementation of auxotrophs is generally much more reliable than usage of antibiotic resistance markers. In order to establish such a system for the model zygomycete Absidia glauca, a stable methionine auxotrophic mutant was isolated after X‐ray mutagenesis of the minus mating type and characterized at the molecular level. The mutant is disrupted in the coding region of the Met2‐1 gene, encoding homoserine O‐acetyltransferase. The corresponding wild type gene was cloned, sequenced and inserted into appropriate vector plasmids. Transformants are prototrophs and show restored methionine‐independent growth, based on complementation by the autonomously replicating plasmids.