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

Recent genomic comparisons of Toxoplasma, Neospora, and Hammondia (the closest extant relative of T. gondii) have identified a series of ROP proteins whose expression targets hostspecific immune signaling pathways. ROP5, ROP16, and ROP18 have all been shown to affect parasite virulence and contribute to host specialization in the mouse model (4, 5) . Recently, an expanded repertoire of SRS proteins, previously implicated in host range expansion of T. gondii, were also identified in Neospora (7) . Modeling of T. gondii metabolism also identified strain-specific differences in growth potential, establishing metabolism as an evolutionary factor capable of influencing host adaptation (8) . To complement the recently generated Eimeria genome sequences and understand the transition from a purely enteric, monoxenous life cycle (e.g., Eimeria) to a heteroxenous one that includes the formation of tissue cysts, we sequenced the genome of Sarcocystis neurona.