The Toxoplasma genome encodes the capacity for distinct architectures underlying cell cycle progression in a life cycle stage-dependent manner. Replication in intermediate hosts occurs by endodyogeny, whereas a hybrid of schizogony and endopolygeny occurs in the gut of the definitive feline host. Here, we characterize the consequence of the loss of a cell cycle-regulated ovarian tumor (OTU family) deubiquitinase, OTUD3A of Toxoplasma gondii (TgOTUD3A; TGGT1_258780), in T. gondii tachyzoites. Rather than the mutation being detrimental, mutant parasites exhibited a fitness advantage, outcompeting the wild type. This phenotype was due to roughly one-third of TgOTUD3A-knockout (TgOTUD3A-KO) tachyzoites exhibiting deviations from endodyogeny by employing replication strategies that produced 3, 4, or 5 viable progeny within a gravid mother instead of the usual 2. We established the mechanistic basis underlying these altered replication strategies to be a dysregulation of centrosome duplication, causing a transient loss of stoichiometry between the inner and outer cores that resulted in a failure to terminate S phase at the attainment of 2N ploidy and/or the decoupling of mitosis and cytokinesis. The resulting dysregulation manifested as deviations in the normal transitions from S phase to mitosis (S/M) (endopolygeny-like) or M phase to cytokinesis (M/C) (schizogony-like). Notably, these imbalances are corrected prior to cytokinesis, resulting in the generation of normal progeny. Our findings suggest that decisions regarding the utilization of specific cell cycle architectures are controlled by a ubiquitin-mediated mechanism that is dependent on the absolute threshold levels of an as-yet-unknown target(s). Analysis of the TgOTUD3A-KO mutant provides new insights into mechanisms underlying the plasticity of apicomplexan cell cycle architecture.
Digital Object Identifier (DOI)
This work was supported by Kentucky Science and Engineering Foundation grant number KSEF-2624-RDE-015 and National Institutes of Health grant number NIH R21 AI122894 (both awarded to A.P.S.).
Supplemental material for this article may be found at https://doi.org/10.1128/mBio.01846-17.
Dhara, Animesh; de Paula Baptista, Rodrigo; Kissinger, Jessica C.; Snow, Ernest Charles; and Sinai, Anthony P., "Ablation of an Ovarian Tumor Family Deubiquitinase Exposes the Underlying Regulation Governing the Plasticity of Cell Cycle Progression in Toxoplasma gondii" (2017). Microbiology, Immunology, and Molecular Genetics Faculty Publications. 96.
inline-supplementary-material-1.tif (184 kB)
inline-supplementary-material-2.tif (421 kB)
inline-supplementary-material-3.tif (339 kB)
inline-supplementary-material-4.tif (458 kB)
inline-supplementary-material-5.tif (282 kB)
inline-supplementary-material-6.tif (631 kB)
inline-supplementary-material-8.tif (13191 kB)
inline-supplementary-material-9.pdf (113 kB)