Variability of the Pr77 sequence of L1Tc retrotransposon among six T. cruzi strains belonging to different discrete typing units (DTUs)

Abstract

All trypanosomatid genomes are colonized by non-LTR retrotransposons which exhibit a highly conserved 77-nt sequence at their 5′ ends, known as the Pr77-hallmark (Pr77). The wide distribution of Pr77 is expected to be related to the gene regulation processes in these organisms as it has promoter and HDV-like ribozyme activities at the DNA and RNA levels, respectively. The identification of Pr77 hallmark-bearing retrotransposons and the study of the associations of mobile elements with relevant genes have been analyzed in the genomes of six strains of Trypanosoma cruzi belonging to different discrete typing units (DTUs) and with different geographical origins and host/vectors. The genomes have been sequenced, assembled and annotated. BUSCO analyses indicated a good quality for the assemblies that were used in comparative analyses. The results show differences among the six genomes in the copy number of genes related to virulence processes, the abundance of retrotransposons bearing the Pr77 sequence and the presence of the Pr77 hallmarks not associated with retroelements. The analyses also show frequent associations of Pr77-bearing retrotransposons and single Pr77 hallmarks with genes coding for trans-sialidases, RHS, MASP or hypothetical proteins, showing variable proportion depending on the type of retroelement, gene class and parasite strain. These differences in the genomic distribution of active retroelements and other Pr77-containing elements have shaped the genome architecture of these six strains and might be contributing to the phenotypic variability existing among them