Architecture, Chromatin and Gene Organization of Toxoplasma gondii Subtelomeres

SUSANA M. CONTRERAS; CRISTALDI, CONSTANZA; ROMINA T. ZAMBRANO SIRI; LAURA KAMENETZKY; MARINA CLEMENTE; ANGEL, SERGIO O.; JOSEFINA OCAMPO; ELÍAS M. RIVERA; KAMI KIM; VANAGAS, LAURA

epigenomes

MDPI

Año: 2022

2075-4655

Subtelomeres (ST) are chromosome regions that separate telomeres from euchromatin andplay relevant roles in various biological processes of the cell. While their functions are conserved,ST structure and genetic compositions are unique to each species. This study aims to identifyand characterize the subtelomeric regions of the 13 Toxoplasma gondii chromosomes of the Me49strain. Here, STs were defined at chromosome ends based on poor gene density. The length ofSTs ranges from 8.1 to 232.4 kbp, with a gene density of 0.049 genes/kbp, lower than the Me49genome (0.15 kbp). Chromatin organization showed that H3K9me3, H2A.X, and H3.3 are highlyenriched near telomeres and the 50 end of silenced genes, decaying in intensity towards euchromatin.H3K4me3 and H2A.Z/H2B.Z are shown to be enriched in the 50 end of the ST genes. Satellite DNAwas detected in almost all STs, mainly the sat350 family and a novel satellite named sat240. Beyondthe STs, only short dispersed fragments of sat240 and sat350 were found. Within STs, there were12 functional annotated genes, 59 with unknown functions (Hypothetical proteins), 15 from multigeneFamB, and 13 from multigene family FamC. Some genes presented low interstrain synteny associatedwith the presence of satellite DNA. Orthologues of FamB and FamC were also detected in Neosporacaninum and Hammondia hammondi. A re-analysis of previous transcriptomic data indicated thatST gene expression is strongly linked to the adaptation to different situations such as extracellularpassage (evolve and resequencing study) and changes in metabolism (lack of acetyl-CoA cofactor).In conclusion, the ST region of the T. gondii chromosomes was defined, the STs genes were determined,and it was possible to associate them with high interstrain plasticity and a role in the adaptability ofT. gondii to environmental changes.