Secondary structure proposed for representative members of the family Avsunviroidae. (Top) Secondary structure of variant X52041, which differs in just one substitution (C123 to U) from the reference variant of the exemplar isolate of avocado sunblotch viroid (J02020, species Avocado sunblotch viroid, genus Avsunviroid) as determined by in vivo SHAPE (López-Carrasco and Flores 2017). (Middle) Secondary structure proposed for the reference variant of the exemplar isolate of peach latent mosaic viroid (M83545, species Peach latent mosaic viroid, genus Pelamoviroid) (Hernández and Flores 1992); a similar structure was confirmed by in vitro SHAPE using another variant of PLMVd (Giguère et al., 2014). (Bottom) Secondary structure of the reference variant of the exemplar isolate of eggplant latent viroid (AJ536613, species Eggplant latent viroid, genus Elaviroid) as determined by in vitro SHAPE (López-Carrasco et al., 2016, Giguère et al., 2014). In the three panels, (+) and (-) sequence motifs conserved in most natural hammerhead structures are indicated by boxes, and self-cleavage sites by arrows. Closed and open boxes indicate the location of the hammerhead structures in the (+) and (-) strands, respectively. In the middle panel, residues involved in a kissing-loop interaction are indicated by red broken lines.