Transformation of the cultivated mushroom, Agaricus bisporus, to hygromycin B resistance.

Application of biotechnology to the cultivated mushroom, Agaricus bisporus, has been hampered thus far by the lack of a transformation system. Here, transformation of both a homo- and a heterokaryotic strain of A. bisporus to hygromycin B resistance is described. Transforming DNA was integrated into the A. bisporus genome and stably maintained throughout vegetative growth. Transformants of the heterokaryotic strain formed transgenic fruiting bodies. Promoters derived from the unrelated ascomycete Aspergillus nidulans and from A. bisporus itself, were able to drive expression of the hygromycin B resistance gene. Expression controlled by a fragment of 265 bp from the A. bisporus GPD promoter was sufficient to generate transformants. However, transformation efficiency was not enhanced by using this homologous promoter.