title: The ectomycorrhizal basidiomycete Hebeloma circinans harbors a linear plasmid encoding a DNA- and RNA polymerase.
abstract: Bulk DNA isolated from the ectomycorrhizal basidiomycete Hebeloma circinans was treated with proteinase K and submitted to agarose gel electrophoresis. In addition to high molecular weight genomic DNA, three minor bands were detected. The band with the highest electrophoretic mobility (2.2 kbp) corresponds to double-stranded RNA. The two other bands, termed pHC1 and pHC2, were shown to be dsDNA molecules of 10.3 and 9.1 kbp, respectively. Treatment of the pHC elements with 3'- and 5'-specific exonucleases revealed a linear structure and proved that the 5' ends are protected from digestion; for pHC2, linearity was confirmed by restriction mapping. A 3.2 kbp HindIII fragment of pHC2 was cloned and sequenced; it contains two open reading frames encoding putative viral B type DNA and RNA polymerases. Thus, the fungus harbors a typical linear plasmid, up to now, rarely described for basidiomycetes and hitherto unknown for mycorrhizal species.
authors.affiliation: Westfälische Wilhelms-Universität Münster, Institut für Mikrobiologie, Corrensstrasse 3, 48149 Münster, Germany.
authors.forename: Xiyuan
authors.initials: X
authors.lastname: Bai
authors.forename: Jean Claude
authors.initials: JC
authors.lastname: Debaud
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schründer
authors.forename: Friedhelm
authors.initials: F
authors.lastname: Meinhardt