Cloning of the Aspergillus oryzae 5-aminolevulinate synthase gene and its use as a selectable marker

The hemA gene encoding 5-aminolevulinate synthase, the first enzyme in heme biosynthesis, was cloned from Aspergillus oryzae and evaluated as a select able marker for the transformation of filamentous fungi. Deletion of the he mA gene resulted in a lethal phenotype that could be rescued either by the supplementation of culture media with 5-aminolevulinic acid (ALA) or by tra nsformation with the wild-type hemA gene, but not by growth on rich media, nor by the addition of exogenous heme. Transformation of a hemA deletion st rain with the hemA gene linked to a lipase expression cassette yielded ALA prototrophs expressing lipase. The hemA gene can therefore be used as a sel ectable marker for the transformation of A. oryzae.