A novel YGGT family protein is localized in the apicoplast and is essential for the organelle inheritance

<i>Toxoplasma gondii</i> is an obligate intracellular apicomplexan parasite. Most apicomplexan parasites contain an endosymbiont-derived organelle called the apicoplast. This organelle is critical for the survival of parasites because it plays a role in several essential metabolic pathways. However, the molecular mechanisms involved in maintaining the apicoplast have not been well understood. In this study, we investigated the function of an apicoplast-residing protein called <i>Tg</i>YCAP in the inheritance of the apicoplast. Our results showed that conditional knockdown of <i>Tg</i>YCAP severely inhibited the growth of the parasite and disrupted the inheritance of the apicoplast. In addition, the YGGT domain is essential for its function in the apicoplast.