Mapping and expression of microneme genes in Eimeria tenella

Microneme organelles are located at the apical tip of invading stages of al l apicomplexan parasites and they contain proteins that are critical for pa rasite adhesion to host cells. In this paper, we have utilised the process of oocyst sporulation in Eimeria tenella to investigate the timing of expre ssion of components of the microneme organelle, at both mRNA and protein le vels. Two time-course studies showed that there is a high level of synchron y in the sporulation process, especially during the time period when sporoz oites are formed. Western blotting showed that the expression of five micro neme proteins (EtMIC1-5) is differentially regulated and highly co-ordinate d during sporulation with the proteins being detected only towards the end of the process, as the sporozoites matured within the sporocysts. In contra st, mRNA for all five of these microneme proteins was detected some 10-12 h earlier in sporulation than when the corresponding proteins were seen. Ove rall these data suggest that the expression of proteins destined for the: m icroneme is regulated both at the transcriptional and translational level. The single copy genes encoding EtMIC1-5 are not clustered on the genome, bu t are found on four different chromosomes. (C) 2000 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.