Whole-genome assembly of a hybrid Trypanosoma cruzi strain assembled with Nanopore sequencing alone.

ABSTRACT

Trypanosoma cruzi is the causative agent of Chagas disease, which causes 10,000 deaths per year. Despite the high mortality associated with Chagas, relatively few parasite genomes have been assembled to date, with genome assemblies unavailable even for some commonly used laboratory strains. This is at least partially due to T. cruzi's highly complex and highly repetitive genome, which defies investigation using traditional short-read sequencing methods. In this study, we have generated a high-quality whole-genome assembly of the hybrid Tulahuen strain, a commercially available type VI strain, using long-read Nanopore sequencing without short-read scaffolding. The assembled genome contains 25% repeat regions, 17% variable multigene family members, and 27% transposable elements (TEs) and is of comparable quality with T. cruzi genome assemblies that utilized both long- and short-read data. Notably, we find that regions with TEs are significantly enriched for multicopy surface proteins, and that surface proteins are, on average, closer to TEs than to other coding regions. This finding suggests that mobile genetic elements such as transposons may drive recombination within surface protein gene families. This work demonstrates the feasibility of Nanopore sequencing to resolve complex regions of T. cruzi genomes, and with these resolved regions, provides support for a possible mechanism for genomic diversification.