Preliminary Findings of DNA Transfer from Transgenic Plants to a Wild-Type Strain of Aspergillus niger

Abstract

Nine different field isolates of bacteria and fungi were cocultivated with four species of transgenic plants or leaf material expressing the hygromycin B resistance gene (hph) in sterile microcosms to determine the possibility of gene transfer events of the resistance gene to the microorganisms. Significantly higher resistance levels were detected only for the filamentous fungus Aspergillus niger after coculture, reisolation and selection of propagated fungus material. The hph-gene, other vector sequences and plant specific sequences were detected in the DNA of some resistant colonies and in a recloned plasmid. However, the mitotic stability seemed to be low. Results of transformation experiments in the fungus with plant transforming vectors gave rise to the assumption that a high gene dose of the 35S-promoted hph-gene was necessary to resist the selection pressure. High cotransformation efficiencies and the recovering of altered vector plasmids from uncut DNA of transformed clones indicated a high recombination activity in fungal cells. The possible uptake of foreign DNA might have occured during the growth of fungal hyphae on the plant material. A special role of hyphal tips as the location of active growth and protein secretion could be assumed.