Craver Mary Patricia J, Rooney Peggy J, Knoll Laura J
Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, United States.
Mol Biochem Parasitol. 2010 Feb;169(2):120-3. doi: 10.1016/j.molbiopara.2009.10.006. Epub 2009 Oct 30.
Within warm-blooded animals, Toxoplasma gondii switches from an actively replicating form called a tachyzoite into a slow growing encysted form called a bradyzoite. To uncover the genes involved in bradyzoite development, we screened over 8000 T. gondii insertional mutants by immunofluorescence microscopy. We identified nine bradyzoite development mutants that were defective in both cyst wall formation and expression of a bradyzoite specific heat shock protein. One of these mutants, named 42F5, contained an insertion into the predicted gene TGME49_097520. The disrupted protein is serine/proline-rich with homology to proteophosphoglycans from Leishmania. T. gondii proteophosphoglycan (GU182879) expressed from the native promoter was undetectable in tachyzoites, but bradyzoites show punctate spots within the parasite and staining around the parasitophorous vacuole. Complementation of the 42F5 mutant with GU182879 expressed from either the alpha-tubulin or native promoter restores cyst wall formation. Overall, GU182879 is upregulated in bradyzoites and enhances cyst wall component expression and assembly.
在温血动物体内，刚地弓形虫会从一种名为速殖子的活跃复制形式转变为一种生长缓慢的包囊形式，即缓殖子。为了揭示参与缓殖子发育的基因，我们通过免疫荧光显微镜对8000多个刚地弓形虫插入突变体进行了筛选。我们鉴定出9个缓殖子发育突变体，它们在包囊壁形成和一种缓殖子特异性热休克蛋白的表达方面均存在缺陷。其中一个名为42F5的突变体，其预测基因TGME49_097520发生了插入。被破坏的蛋白质富含丝氨酸/脯氨酸，与利什曼原虫的蛋白磷酸聚糖具有同源性。从天然启动子表达的刚地弓形虫蛋白磷酸聚糖（GU182879）在速殖子中无法检测到，但缓殖子在寄生虫体内显示出点状斑点，并在寄生泡周围染色。用从α-微管蛋白或天然启动子表达的GU182879对42F5突变体进行互补，可恢复包囊壁的形成。总体而言，GU182879在缓殖子中上调，并增强包囊壁成分的表达和组装。
