Calypso is a LTR retroelement found in the genome Glycine max (Peterson-Burch et al. 2000). Calypso belongs to Athila clade, a lineage of possible retroviruses in plants (Wright and Voytas 2002), which is sibling of Tat clade, a lineage of plant LTR retrotransposons. Both lineages provide evidence of a shared ancestral lineage originally described as Class A by Wright and Voytas (1998). The full-length consensus for Calypso is 13 Kb in size including LTRs of 1.8 Kb. The internal region of this element displays a Primer Binding Site (PBS) complementary to a tRNAAsp, three Open Reading Frames (ORFs) for gag, pol, and env genes, and two Polypurine Tracts, PPT1 and PPT2, adjacent to the 3´LTR (Wright and Voytas 2002).
Figure not to scale. If present, long terminal repeats (LTRs) have been highlighted in blue. Amino acid motifs noted with lines indicate the conserved residues in each protein domain, abbreviations below mean:
|DU or DUT=dUTPase
|TAV or IBMP=transactivator/viroplasmin or inclusion body matrix protein
|PBS=primer binding site
|ATF=aphid transmission factor
|VAP=virion associated protein