Fig. 4

Retrozymes in the genome of the strawberry (Fragaria ananassa). a Northern blot analysis of RNA extracts (~20 μg) of F. ananassa flowers and leaves carried out as described in Fig. 3. One ng of a (+)RNA transcript of F. ananassa was included as a marker. The positions of the linear and circular RNAs are indicated. Approximate positions of the bands corresponding to the RNA marker are indicated for clarity. b Northern blot analysis of RNA extracts (~20 μg) of F. ananassa flowers and leaves run in a 5 % denaturing polyacrylamide gel and detected using a F. ananassa retrozyme fragment of the positive polarity as a probe. 0.1 ng of a (–)RNA transcript of F. ananassa was included. Ethidium bromide staining of the 5S rRNA band is shown at the bottom of panels a and b as a loading control. c Minimum free energy secondary structure prediction for a retrozyme RNA from F. ananassa leaves (clone Fa_049, 674 nt). Numbering, colors and natural sequence heterogeneity are shown as in Fig. 3. d Schematic representation of the circular retrozyme RNA and the position of the oligos used for RT and PCR experiments