Analysis for Pathogenicity and Development of Transgenic Eimeria tenella Expressing both Yellow Fluorescent Protein and TgDHFR-TS Genes

In order to determine the effect of foreign genes on a transgenic parasite,the pathogenicity and development in chickens of transgenic E.tenella strain TE1,which expresses yellow fluorescent protein (YFP) and dihydrofolate reductase thymidylate synthase derived from Toxoplasma gondii(TgDHFR-TS), were compared with that of the parental strain BJ.Results indicated that the fecundity of the transgenic parasite(TE1) was reduced at least 4 times relative to that of the BJ strain.Low dosage of the TE1 strain induced less pathogenesis in chickens than did the BJ strain,but chickens inoculated with a higher dosage of TE1 oocysts displayed severe pathogenicity and mortality as did the BJ strain.In addition,trophozoites, the first generation and the second generation meronts and merozoites,microgamonts and macrogamonts of the transgenic parasite TE1 were seen by fluorescence microscopy.More interestingly,not all four sporonts in the sporulating transgenic oocysts express YFP.These findings suggest that the expression of YFP and TgDHFR-TS genes to some extent reduced pathogenicity and reproductive potential of transgenic E.tenella.Recombination between homologous or non-homologous chromosomes occurred during zygotic meiosis in E.tenella strain TE1.