Different classes of retrotransposons in coniferous spruce species.

We have used the conservation of reverse transcriptase and integrase domains among retroelements to PCR-amplify three well-known types of these mobile genetic elements. Reverse transcriptase sequences from Ty1-copia were identified in spruce in this way, as well as integrase sequences from the Ty3-gypsy group. Using these sequences as probes against a Picea glauca genomic bank, individual members from the LTR (long terminal direct repeat) groups were obtained. A partial Ty1-copia-type element named Spcl was isolated along with a Ty3-gypsy-type element named Spdl. Genomic Southern hybridizations revealed the complexity and high copy number of LTR retrotransposons in black and white spruce.