TY - JOUR TI - Dissection of the in vitro developmental program of Hammondia hammondi reveals a link between stress sensitivity and life cycle flexibility in Toxoplasma gondii AU - Sokol, Sarah L AU - Primack, Abby S AU - Nair, Sethu C AU - Wong, Zhee S AU - Tembo, Maiwase AU - Verma, Shiv K AU - Cerqueira-Cezar, Camila K AU - Dubey, JP AU - Boyle, Jon P A2 - Soldati-Favre, Dominique VL - 7 PY - 2018 DA - 2018/05/22 SP - e36491 C1 - eLife 2018;7:e36491 DO - 10.7554/eLife.36491 UR - https://doi.org/10.7554/eLife.36491 AB - Most eukaryotic parasites are obligately heteroxenous, requiring sequential infection of different host species in order to survive. Toxoplasma gondii is a rare exception to this rule, having a uniquely facultative heteroxenous life cycle. To understand the origins of this phenomenon, we compared development and stress responses in T. gondii to those of its its obligately heteroxenous relative, Hammondia hammondi and have identified multiple H. hammondi growth states that are distinct from those in T. gondii. Of these, the most dramatic difference was that H. hammondi was refractory to stressors that robustly induce cyst formation in T. gondii, and this was reflected most dramatically in its unchanging transcriptome after stress exposure. We also found that H. hammondi could be propagated in vitro for up to 8 days post-excystation, and we exploited this to generate the first ever transgenic H. hammondi line. Overall our data show that H. hammondi zoites grow as stringently regulated, unique life stages that are distinct from T. gondii tachyzoites, and implicate stress sensitivity as a potential developmental innovation that increased the flexibility of the T. gondii life cycle. KW - Toxoplasma gondii KW - Hammondia hammondi KW - tissue cyst KW - bradyzoite KW - transcriptome KW - stress sensitivity JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -