The genome of Eimeria spp., with special reference to Eimeria tenella - a coccidium from the chicken

Eimeria spp. contain at least four genomes. The nuclear genome is best stud ied in the avian species Eimeria tenella and comprises about 60 Mbp DNA con tained within ca. 14 chromosomes: other avian and lupine species appear to possess a nuclear genome of similar size. In addition, sequence data and hy bridisation studies have provided direct evidence for extrachromosomal mito chondrial and plastid DNA genomes, and double-stranded RNA segments have al so been described. The unique phenotype of "precocious" development that ch aracterises some selected lines of Eimeria spp. not only provides the basis for the first generation of live attenuated vaccines, but offers a signifi cant entree into studies on the regulation of an apicomplexan life-cycle. n e With a view to identifying loci implicated in the trait of precocious dev elopment, a genetic linkage map of the genome of E. tenella is being constr ucted in this laboratory from analyses of the inheritance of over 400 polym orphic DNA markers in the progeny of a cross between complementary drug-res istant and precocious parents. Other projects that impinge directly or indi rectly on the genome and/or genetics of Eimeria spp. are currently in progr ess in several laboratories, and include the derivation of expressed sequen ce tag data and the development of ancillary technologies such as transfect ion techniques. No large-scale genomic DNA sequencing projects have been re ported. (C) 2000 Published by Elsevier Science Ltd on behalf of the Austral ian Society for Parasitology Inc. All rights reserved.