Key roles of amylopectin synthesis and degradation enzymes in the establishment and reactivation of chronic toxoplasmosis

Abstract Toxoplasma gondii ( T. ) is an obligate intracellular parasite with a wide range of hosts, including humans and many warm-blooded animals. The exists in two interconvertible forms, namely tachyzoites bradyzoites intermediate hosts that are responsible for acute chronic infections respectively. Mature accumulate large amounts amylopectin granules but their roles have not been fully characterized. In this study, the predicted key enzymes involved synthesis (UDP-sugar pyrophospharylase, USP) degradation (alpha-glucan water dikinase, GWD) ME49 strain were individually knocked out, then bradyzoite-related phenotyping experiments vitro vivo performed to dissect during growth development. Deletion usp or gwd gene type II reduced replication rates virulence vivo, suggesting metabolism important optimal tachyzoite growth. Interestingly, Δusp mutant grew slightly faster than parental under stress conditions induced bradyzoite transition, which was likely due decreased efficiency formation mutant. Although Δgwd could convert robustly vitro, it significantly impaired establishing infection vivo. Both mutants showed dramatic reduction reactivation model. Together, these results suggest USP GWD, growth, as well .