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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Parasitic Diseases Laboratory » Research » Publications at this Location » Publication #336721

Research Project: Detection and Control of Foodborne Parasites for Food Safety

Location: Animal Parasitic Diseases Laboratory

Title: The aromatic amino acid hydroxylase genes AAH1 and AAH2 in Toxoplasma gondii contribute to transmission in the cat

Author
item Wang, Zit - Washington University School Of Medicine
item Verma, Shiv - Non ARS Employee
item Dubey, Jitender
item Sibley, Lawrence - Washington University School Of Medicine

Submitted to: PLoS Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2017
Publication Date: 3/13/2017
Citation: Wang, Z., Verma, S., Dubey, J.P., Sibley, L. 2017. The aromatic amino acid hydroxylase genes AAH1 and AAH2 in Toxoplasma gondii contribute to transmission in the cat. PLoS Pathogens. 13(3):e1006272.

Interpretive Summary: Toxoplasma gondii is an intracellular parasite that infects up to one-quarter of humans worldwide. Although it can infect virtually any warmblooded animal, its definitive host is the cat where the sexual cycle occurs in enterocytes of the small intestine, producing microscopic, durable oocysts that are shed in feces and can remain infectious for extended periods of time in the environment. Of all known hosts, only cats can shed oocysts. Two parasite genes, AAH1 and AAH2, code for aromatic amino acid hydroxylases, which produce L-DOPA, the precursor to dopamine are thought to influence behavior in the infected hosts. In this paper, the authors found that removal of of the AAH genes resulted in reduced infection in the cat, lower oocyst yields, and decreased rates of sporulation. These findings suggest that the AAH genes play a predominant role in the development and maturation of the oocyst stage during the sexual cycle of T. gondii. These results will be of interest to biologists, microbiologists, and parasitologists.

Technical Abstract: The Toxoplasma gondii genome contains two aromatic amino acid hydroxylase genes, AAH1 and AAH2, which encode proteins that produce L-DOPA, which can serve as a precursor of catecholamine neurotransmitters. It has been suggested that this pathway elevates host dopamine levels thus making infected rodents less fearful of their definitive Felidae hosts. However, L-DOPA is also a structural precursor of melanins, secondary quinones, and dityrosine protein crosslinks, which are produced by many species. For example, dityrosine plays a major structural role in the oocyst walls of Eimeria and T. gondii. Here, we investigated the biology of AAH knockout parasites in the sexual reproductive cycle within cats. We found that ablation of the AAH genes resulted in reduced infection in the cat, lower oocyst yields, and decreased rates of sporulation. Our findings suggest that the AAH genes play a predominant role in the development and maturation of the oocyst stage during the sexual cycle of T. gondii.