Characterizing the tachyzoite to bradyzoite stage transition in Toxoplasma gondii

Toxoplasma gondii is an obligate intracellular protozoan parasite that can infect all mammals, including humans. It is estimated that more than one third of the world’s population is infected with T. gondii. Moreover, T. gondii is a close relative, and important molecular model, of Plasmodium falciparum, the causative agent of malaria. Acute and latent toxoplasmosis, the disease caused by T. gondii, involves the tachyzoite and bradyozoite forms of the parasite, respectively, and is generally asymptomatic. On the other hand, toxoplasmosis is one of the leading causes of fetal malformations and deaths in immunocompromised individuals, and has been linked to risky behavior and suicidal tendencies. Furthermore, the transition from tachyzoite to bradyozoite is poorly characterized. To better understand this shift, RNA was extracted from parasites undergoing the tachyzoite to bradyozoite conversion and was submitted for microarray analysis. In total, 71 genes, comprising 0.81% of the T. gondii transcriptome, were up-regulated early in the transition. Of these early up-regulated genes, 22 (31%) contained a 25 bp thymidine-rich consensus motif in their upstream regions. In addition, a hypothetical T. gondii transcription factor binds to this consensus motif and therefore poses a pivotal target for the development a T. gondii vaccine through its deletion