Ryan, Rachel Mary;
(2002)
Expression of microneme genes in Eimeria tenella.
Doctoral thesis (Ph.D), UCL (University College London).
![[thumbnail of out.pdf]](https://discovery.ucl.ac.uk/style/images/fileicons/text.png) |
Text
out.pdf Download (15MB) |
Abstract
Micronemal proteins, which are released from membrane-bound secretory organelles from invasive stages of the protozoan parasite Eimeria tenella, are believed to function as specialised adhesins, essential for substrate-dependent parasite motility and invasion of host cells. Little is known about the regulation of microneme protein expression, but ultrastructural studies suggest that micronemes are formed afresh during each successive zoite stage, appearing as the parasites mature. I set out to examine one broad aspect of the biology of microneme organelle formation, viz. the ways in which the appearance of some microneme proteins are regulated. A starting point was the development of an experimental system (oocyst sporulation leading to the formation of invasive sporozoites) so that events occurring during the de novo formation of micronemes could be examined. The sporulation of oocysts proved an excellent system to investigate the timings of expression of microneme proteins at both the mRNA and mature protein level. The appearance of microneme proteins, EtMIC1-5, was initially found to be highly co-ordinated as sporozoites matured (~22.5 h). RT-PCR analyses indicated that microneme-specific mRNAs were present after 6-12 h of sporulation and the level of synchronicity observed, suggested that expression was highly regulated. The locations of the microneme-coding genes within the genome was unlikely to be responsible for the co-ordination as the genes were found on different chromosomes. DNA sequence and 5'RACE analyses of the upstream regions of the genes EtMIC1-5 were undertaken and initiator regions surrounding the transcriptional start sites of the genes were identified - similar sequences are present in other genes from a variety of apicomplexan parasites. Transient transfection assays of E. tenella undertaken to identify the minimum promoter of the genes EtMIC1 and 2 revealed that 234 and 131 bp, respectively upstream of the ATG start codon were sufficient for expression. The initiator alone of EtMIC1 was not capable of driving gene expression, whereas the initiator of EtMIC2 was sufficient for basal level expression. Mutational analysis of the initiators of EtMIC1 and 2 identified motifs and nucleotides within these motifs that make an important contribution to gene expression.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Expression of microneme genes in Eimeria tenella |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| Keywords: | Biological sciences; Eimeria tenella |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10104543 |
Loading...
Loading...Loading...Loading...Archive Staff Only
 |
View Item |
