EC Accepts, published online ahead of print on 6 November 2009

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Eukaryotic Cell doi:10.1128/EC.00255-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

The glycosylation pathway of Eimeria tenella is upregulated during gametocyte development and may play a role in oocyst wall formation

Robert A. Walker, Iveta Slapetova, Jan Slapeta, Catherine M. Miller, and Nicholas C. Smith^*

Institute for the Biotechnology of Infectious Diseases, University of Technology, Sydney, NSW, 2007, Australia

^* To whom correspondence should be addressed. Email: Nick.Smith{at}uts.edu.au.

Sexual stage glycoproteins of Eimeria are important components of the oocyst wall, a structure that ensures the efficient transmission of these and related parasites. In this study, the primary enzyme in the glycosylation pathway of Eimeria tenella, glucosamine: fructose-6-phosphate aminotransferase (EtGFAT), has been characterised as a macrogamete-specific protein. While transcription of EtGFAT was observed early in macrogamete development, protein expression was restricted to mature macrogametes, prior to their conversion into unsporulated oocysts. Genes coding for three other enzymes required for N-acetylgalactosamine (GalNAc) synthesis were also transcribed during E. tenella macrogamete development. Gene transcription of the enzyme responsible for the O-linked transfer of GalNAc to proteins, EtGalNAc-T, was upregulated primarily in unsporulated oocysts stages and, accordingly, a significant increase in GalNAc levels was observed in E. tenella gametocytes and oocysts. Gam56 and Gam82, two well characterised glycoproteins of Eimeria macrogametes and the oocyst wall, contain high levels of GalNAc and represent probable targets of GalNAc O-linkage. It appears that the glycosylation pathway, specifically relating to the formation of GalNAc O-links, is dramatically upregulated in E. tenella sexual stages and may play a role in directing a number of macrogamete proteins to the developing oocyst wall.