Transposable elements (TEs) account for a large portion of plant genomes, particularly in grasses, in which they correspond to 50%-80% of the genomic content. TEs have recently been shown to be a source of new genes and new regulatory networks. The most striking contribution of TEs is referred as “molecular domestication”, by which the element coding sequence loses its movement capacity and acquires cellular function. Recently, domesticated transposases known as mustang and derived from the Mutator element have been described in sugarcane. In order to improve our understanding of the function of these proteins, we identified mustang genes from Sorghum bicolor and Zea mays and performed a phenetic analysis to assess the diversity and evolutionary history of this gene family. This analysis identified orthologous groups and showed that mustang genes are highly conserved in grass genomes. We also explored the transcriptional activity of sugarcane mustang genes in heterologous and homologous systems. These genes were found to be ubiquitously transcribed, with shoot apical meristem having the highest expression levels, and were downregulated by phytohormones. Together, these findings suggest the possible involvement of mustang proteins in the maintenance of hormonal homeostasis.

O projeto de ESTs (Expressed sequence tag) da canade-açúcar (SUCEST) produziu um grande número de seqüências de cDNA de diferentes tecidos submetidos ou não a diferentes condições de estresse. Neste trabalho nós analisamos os resultados de uma busca, por Elementos de Transposição (TEs), que apresentou um grande numero de seqüências homólogas a TEs. Das 260.781 seqüências agrupadas em 81.223 clusters pelo programa Phrap (fragment assembly program), um total de 276 seqüências apresentaram homologia com TEs previamente descritos utilizando-se uma nota de corte estringente de 50 ou melhor. Clones homólogos aos grupos de retrotransposons com LTR (long terminal repeat) copia/Ty1 e Gypsy/ty3 foram achados porém nenhum retroelemento sem LTR foi identificado. A maioria das famílias de transposons estão representadas em cana-de-açucar incluindo Activator (Ac), Mutator (MuDR), Supressor-mutator (En/Spm) e Mariner. Para podermos comparar a diversidade dos TEs nos genoams das gramíneas, nós buscamos os TEs em espécies relacionadas a cana-de-açúcar tais como O sativa, Z. mays e S. bicolor. Nós também apresentamos os resultados preliminares do potencial uso de TEs como marcadores moleculares na identificação de cultivares.

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/Ty1 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.