Identification of repeated sequences in Coffea genomes

A library enriched in repeated sequences was obtained from a F1 hybrid issued from a cross between C pseudozanguebariae and C. liberica var. dewevrei. These two species differ in their nuclear DNA content, 1.3 pg and 1.43 pg respectivelly. 193 clones were isolated following retrohybridization. Already 60 clones have been sequenced and show a great proportion of repeated sequences (>90%). In addition to tandemly repeated sequences, several types of retrotransposons have been identified following similitude comparison (BLAST) with data bases. Both types gypsy-like and copia-like are present in Coffea genomes. Furthermore, other LINE retrotransposons were also detected. Probes corresponding to some of these repeated sequences were hybridized to nuclear DNA isolated from several Coffea species: C rasemosa, C. sessiflora, C. eugenioides, C. sp. Moloundou, C. canephora, C. congensis and C. heterocalyx. All the species contained sequencies similar to the used probes but the restriction pattern were different and identical phylogenetic groups to those determined by ribosomal DNA could be identified. Importance of repeated sequences in speciation of Coffea genus and their role in F1 sterility will be discussed. (Texte intégral