Survey of transposable elements in sugarcane expressed sequence tags (ESTs)

The sugarcane expressed sequence tag (SUCEST) project has produced a large number of cDNA sequences from several plant tissues submitted or not to different conditions of stress. In this paper we report the result of a search for transposable elements (TEs) revealing a surprising amount of expressed TEs homologues. Of the 260,781 sequences grouped in 81,223 fragment assembly program (Phrap) clusters, a total of 276 clones showed homology to previously reported TEs using a stringent cut-off value of e-50 or better. Homologous clones to Copia/Tyl and Gypsy/Ty3 groups of long terminal repeat (LTR) retrotransposons were found but no non-LTR retroelements were identified. All major transposon families were represented in sugarcane including Activator (Ac), Mutator (MuDR), Suppressor-mutator (En/Spm) and Mariner. In order to compare the TE diversity in grasses genomes, we carried out a search for TEs described in sugarcane related species O.sativa, Z. mays and S. bicolor. We also present preliminary results showing the potential use of TEs insertion pattern polymorphism as molecular markers for cultivar identification.