Sequence heterogeneity of theenvelope-like domain in cultivated allotetraploidGossypium species and their diploid progenitors
The objective of the current study was to analyze Ty1-copia group retrotransposons in cultivated G. barbadense L. cottons. DNA sequence analysis of 27 partial reverse transcriptase sequences revealed that these elements are heterogeneous and this heterogeneity is resolved into 11 distinct families. Phylogenetic analyses provided strong bootstrap support for a monophyletic origin of plant Ty1-copia group retrotransposons, yet showed high diversity within and between Gossypium species. Furthermore, G. Barbadense element topologies are incongruent with Gossypium phylogeny. The high ratio of synonymous to nonsynonymous changes indicates that the reverse transcriptase domain of these families is evolving under purifying selection. The antiquity and wide distribution of Ty1-copia group retrotransposons illustrate their active role in shaping and evolution of the Gossypium genome.