Systems-Based Analysis of the Sarcocystis neurona Genome Identifies Pathways That Contribute to a Heteroxenous Life Cycle

Blazejewski, Tomasz; Nursimulu, Nirvana; Pszenny, Viviana; Dangoudoubiyam, Sriveny; Namasivayam, Sivaranjani; Chiasson, Melissa A.; Chessman, Kyle; Tonkin, Michelle; Swapna, Lakshmipuram S.; Hung, Stacy S.; Bridgers, Joshua; Ricklefs, Stacy M.; Boulanger, Martin J.; Dubey, Jitender P.; Porcella, Stephen F.; Kissinger, Jessica C.; Howe, Daniel K.; Grigg, Michael E.; Parkinson, John

In general, RONs were well conserved in S. neurona and T. gondii, with RON2, RON3, RON5, and RON8 orthologs displaying significant sequence similarity across their entire length. Three paralogs of T. gondii RON3 (TgRON3) were identified on a single scaffold, suggesting a tandem duplication, two of which appear to be expressed as predicted by the RNA-Seq data. Putative S. neurona orthologs of RON4 and RON6 were identified through manual inspection of sequence alignments. A pattern of conservation and divergence was observed for a putative ortholog of TgRON9. In T. gondii, RON9 and RON10 form a stable complex distinct from the AMA1-RON2/4/5/8 complex, with disruption of either gene leading to the retention of its partner in the endoplasmic reticulum, followed by degradation. This complex does not play a role in T. gondii invasion and virulence but, because of its conservation with C. parvum, has been linked to interactions involving epithelial cells (33) . While an S. neurona protein could be aligned over~25% of the TgRON9 sequence, it was found to lack a single copy of the 22 copies of the PAEENAEEPKQAEEQANASQSSET motif associated with the T. gondii protein. No homologs to RON1 or RON10 could be identified.