Hairpin Plasmids from the Plant Pathogenic Fungi Rhizoctonia solani and Fusarium oxysporum

This review focuses on the biology of the hairpin plasmids from the plant pathogenic fungi Rhizoctonia solani and Fusarium oxysporum. R. solani linear plasmid is single-stranded with covalently closed hairpin loops at each end. F. oxysporum plasmid, however, has a clothespin structure, which includes a terminal hairpin and noncovalently linked ends at the other terminus. We present the nucleotide sequence of the hairpin plasmids, the terminal hairpin structure, an analysis of an open reading frame in the sequence, the unique transcriptional form of this plasmid, and a proposed model for their replication.