Genomic organization of ssDNA virus-like transposons in fungi (A) and lower eukaryotes (B). (A) The genomic organization of geminivirus-like transposon in Tuber melanosporum. Arrowhead boxes indicate ORFs (orange, Rep-like gene; blue, transposase gene). The black vertical lines in the arrowhead boxes indicate stop codons. Green rectangular box indicates microsatellite sequence. The sequence of terminal inverted repeat (TIR) is shown at the top to the right. (B) The genomic organization and comparison of parvovirus-like transposon with related exogenous planaria virus. Yellow arrowhead boxes indicate Rep-like ORFs. Swallow tails indicate terminal inverted repeats (TIRs). The annotated ORF names are indicated. Purple rectangular boxes indicate protein domains and the domain family names are shown: Parvo_NS1, Parvovirus non-structural protein NS1 (pfam01057); Parvo_coat_N, Parvovirus coat protein VP1 (pfam08398); PPV_E1_C, Papillomavirus helicase (pfam00519). Gray sectors connect corresponding homologous regions and the % nucleotide (nt) or amino acid (aa) identity are indicated. The Planaria asexual strain-specific virus-like element has not been found to integrate in the host genome.