Reme1, a Copia retrotransposon in melon, is transcriptionally induced by UV light

Abstract

For the first time, numerous sequences of Copia and Gypsy retrotransposons from the Cucumis melo genome have been obtained and analyzed. Phylogenetic analyses of sequences of both types of long terminal repeat (LTR) retrotransposons were carried out. The melon genome contains approximately 20,000 Gypsy and 6,800 Copia elements, comprising about 26% of its total size. Starting from a retrotransposon fragment, we have cloned and characterized an entire melon retrotransposon, named Reme1, which is 5,149 bp long. Reme1 belongs to the Superfamily Copia retrotransposons by its protein domain order and sequence similarity to other Copia elements of dicotyledons. The haploid genome of melon (var. "Piel de Sapo") contains about 120 copies of Reme1. Several copies of Reme1 are transcriptionally active, although at low levels, in melon leaves as analyzed by reverse-transcription PCR (RT-PCR) and sequencing. However, the transcript pool is considerably increased when melon leaves are treated with UV light, as has been seen for various retroelements in many organisms. The cDNAs of Reme1 transcripts showed less diversity than do Reme1 genomic sequences, suggesting that a subfamily of these elements is differentially responsive to UV.