Authors

A H Abbas²; N Hall¹; C Hertz-Fowler²; A C Darby²;  ¹ Earlham Institute;  ² University of Liverpool

Discussion

Trypanosome Mini-chromosomes (MCs) are important genomic regions as these chromosomes carry genes that help the parasite to avoid host immune system. MCs of T. brucei range in their size from (30 to 100 kbp). However, the sequence of T. congolense MCs is uncovered yet. To unravel the nucleotide sequence of these regions, we used PACBIO single-molecule Real-time sequencing to sequence T. congolense IL3000 gDNA. We generated 1.7 Gb of PACBIO reads with an average read length of 8kb, were assembled with HGAP v3 into 1541 contigs, with total assembly size of ~39Mbp, contig N50 156kb, max contig length 1.4Mb. Seven putative complete T. c  MCs (TcMCs) were identified and 60 partial TcMCs. The structure of the TcMCs can be simplified and subdivide into four regions: 1. A central palindromic repeat with a ~369bp repeating unit, which represents 32% - 65% of the total length of the TcMC. 2. A conserved GC rich sequence of 1.5 - 2kbp. 3. Variable subtelomeric region stretched of ~5Kbp which can contain a number of features which include variant surface glycoprotein genes (VSG). 4. Telomeric repeats. The results suggest that the subtelomeric region 3 are highly variable carrying expression site association genes (ESAG), VSG or DEAH/D box RNA helicase genes. Our findings proposed that the length of the TcMCs depends on the length of the central palindromic repeat region.