Phylogenetic and molecular evolutionary analyses of gypsy group retrotransposon families in the Egyptian cotton Gossypium barbadense

Abstract

Gypsy group retrotransposons in the Egyptian cotton, Gossypium barbadense, was examined by 
phylogenetic and molecular evolutionary analyses. DNA sequences of gypsy group retrotransposons 
in two G. barbadense cultivars revealed that these sequences are heterogeneous and represent two 
distinct families. Sequence variation between these families seems to preserve coding information of 
the reverse transcriptase domain. The high ratio of synonymous to nonsynonymous changes 
indicates that the reverse transcriptase domain of these families is evolving under purifying selection. 
Our phylogenetic analysis revealed that the closest relatives of cotton retroelements are found in 
other plants gypsy group retrotransposons. Cotton retroelements-encoded transcripts were detected 
in their related respective young seedlings using RNA slot-blot hybridization, suggesting their 
transcriptional activity. The wide distribution of gypsy group retrotransposons and the detection of 
their encoded transcripts illustrate their active role in the Gossypium genome.