THE DISTRIBUTION AND ORGANIZATION OF TY1-COPIA-LIKE RETROTRANSPOSABLEELEMENTS IN THE GENOME OF VIGNA-UNGUICULATA (L) WALP (COWPEA) AND ITSRELATIVES

Ty1-copia-like retrotransposable elements were amplified from Vigna sp ecies by the polymerase chain reaction (PCR) with primers derived from the conserved region of the reverse transcriptase (RT) gene. Southern blots of genomic DNA digests from Vigna unguiculata and related speci es probed with the PCR derived sequences from V. unguiculata (rt-cow), V. unguiculata subsp. dekindtiana (rt-dek), V. luteola (rt-lut) and V . vexillata (rt-vex) showed variable hybridization patterns and intens ities, generally correlating with taxonomic relationships. Sequencing of four clones revealed homologies to the reverse transcriptase gene o f known Ty1-copia-like elements, although comparison of the predicted peptide sequences with each other and previously isolated reverse tran scriptase genes from other legumes typically showed less than 50% iden tity. Fluorescence in situ hybridization of the PCR products showed th at Ty1-copia elements represented a major fraction of the genome and w ere dispersed relatively uniformly over all chromosomes, with exclusio n from centromeric, subtelomeric and nucleolar organizing regions, and a few sites of greater abundance. We are now able to start to underst and the organization, variability and evolution of retrotransposons wi thin the Fabaceae. (C) 1997 Annals of Botany Company.