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

Proteins involved in host regulation in T. gondii are not well conserved in S. neurona. In addition to RONs, rhoptries also secrete a battery of ROP proteins, the products of a group of genes displaying high levels of correlated expression (Fig. 3B) . ROP proteins are secreted into the host cytosol to interact with host cell targets, manipulating pathways that protect the intracellular parasite against clearance. To identify putative S. neurona ROP ho- (39) . In addition to the eight SnROPKs reported previously (39), our phylogenetic analysis identified seven new ROPK orthologs, including: ROP20, ROP26, ROP33, ROP34, and ROP45, as well as two SnROPKs that appear unique to S. neurona (Fig. 5A) . RNA-Seq data support the expression of six of these (ROP14, ROP21, ROP27, ROP30, ROP35, and ROP37) during the merozoite stage, despite this stage's lack of rhoptries and the ability of schizonts to develop in host cell cytoplasm in the absence of a PV (3).