biostudies-literatureFu YNIAID NIH HHSNational Institutes of Healthe73011https://www.ebi.ac.uk/biostudies/studies/S-EPMC8683080biostudies-literatureUnknown10<i>Toxoplasma gondii</i> has evolved different developmental stages for disseminating during acute infection (i.e., tachyzoites) and establishing chronic infection (i.e., bradyzoites). Calcium ion (Ca²⁺) signaling tightly regulates the lytic cycle of tachyzoites by controlling microneme secretion and motility to drive egress and cell invasion. However, the roles of Ca²⁺ signaling pathways in bradyzoites remain largely unexplored. Here, we show that Ca²⁺ responses are highly restricted in bradyzoites and that they fail to egress in response to agonists. Development of dual-reporter parasites revealed dampened Ca²⁺ responses and minimal microneme secretion by bradyzoites induced in vitro or harvested from infected mice and tested ex vivo. RatiometreLife<i>Toxoplasma</i> bradyzoites exhibit physiological plasticity of calcium and energy stores controlling motility and egress.PMC8683080R01 AI034036R01 AI164473R01 AI162749R01 AI128356R01 AI143857R21 AI162033AI143857R01 AI118426AI034036AI128356Brown KMJones NGSibley LDFu YMoreno SNfalse<i>Toxoplasma</i> bradyzoites exhibit physiological plasticity of calcium and energy stores controlling motility and egress.<i>Toxoplasma gondii</i> has evolved different developmental stages for disseminating during acute infection (i.e., tachyzoites) and establishing chronic infection (i.e., bradyzoites). Calcium ion (Ca²⁺) signaling tightly regulates the lytic cycle of tachyzoites by controlling microneme secretion and motility to drive egress and cell invasion. However, the roles of Ca²⁺ signaling pathways in bradyzoites remain largely unexplored. Here, we show that Ca²⁺ responses are highly restricted in bradyzoites and that they fail to egress in response to agonists. Development of dual-reporter parasites revealed dampened Ca²⁺ responses and minimal microneme secretion by bradyzoites induced in vitro or harvested from infected mice and tested ex vivo. Ratiometr2021-01-01T00:00:00Z2021 Dec2026-05-09T12:01:54.809Z2022-02-11T15:48:03.772ZS-EPMC86830803486015610.7554/eLife.73011