Plastid in human parasites

• Published in: Nature (London) Vol. 381; no. 6582; p. 482
• Main Authors: McFadden, Geoffrey I, Reith, Michael E, Munholland, Janet, Lang-Unnasch, Naomi
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 06-06-1996
• Subjects: Animals; Genomes; Humans; In Situ Hybridization; Membranes; Microorganisms; Parasites; Plasmodium; Plasmodium falciparum - genetics; Plasmodium falciparum - ultrastructure; Plastids; Protozoa; Ribonucleic acid; RNA; RNA, Ribosomal, 16S - analysis; Toxoplasma - genetics; Toxoplasma - ultrastructure; Toxoplasma gondii
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/381482a0

The discovery in malarial and toxoplasmodial parasites of genes normally occurring in the photosynthetic organelle of plants and algae has prompted speculation that these protozoans might harbour a vestigial plastid. To determine whether a plastid is present, we used high-resolution in situ hybridization to localize transcripts of a plastid-like 16S ribosomal RNA gene from Toxoplasma gondii, the causative agent of toxoplasmosis. Transcripts accumulate in a small, ovoid organelle located anterior to the nucleus in the mid-region of the cell. Our preliminary experiments with Plasmodium falciparum, the causative agent of the most lethal form of malaria, identify an organelle which appears similar to the T. gondii plastid. The presence of a plastid in apicomplexan parasites probably explains their sensitivity to certain herbicides and drugs inhibiting plastid metabolism. The plastid is thus a welcome new, parasite-specific target for therapeutic agents.