Previous studies have shown that the mitochondrial orf224/ atp6 gene region is correlated with the Polima (pol) cytoplasmic male sterility (CMS) of Brassica napus, and that the effects of nuclear fertility restoration on orf224/ atp6 transcripts co-segregate with the pol restorer gene Rfp in genetic crosses. Results presented in this thesis indicate that the pol CMS restorer gene Rfp acts in an organ-specific manner to promote the processing of primary, dicistronic orf224/atp6 transcripts into new restorer-specific, monocistronic transcripts. The single 1.1 kb atp6 transcript of nap cytoplasm and some orfB transcripts of nap and pol cytoplasm B. napus mitochondria are shown to arise by removal of sequences from the 5' end of a longer precursor. Specific endonucleolytic cleavage of a precursor RNA, followed by non-specific 3' to 5' exonuclease action, may thus represent a common mechanism for tailoring transcripts in plant mitochondria. Northern analysis of a segregating F2 population indicates that the recessive rfp allele at the restorer gene locus, or a very tightly linked gene, acts as a dominant gene designated Mmt (modifier of mitochondrial transcripts). Mmt controls the presence of additional, smaller transcripts of the nad4 and ccl1-like (ccl1-l) genes. These results suggest that Rfp/Mmt is a novel nuclear genetic locus that affects the expression of multiple mitochondrial gene regions, with different alleles or haplotypes exerting specific effects on different mitochondrial genes. One of these genes, ccl1-l, is split in the B. napus mitochondrial genome into two widely separated and independently transcribed parts, contrasting with the situation in other plants where this gene is present as an uninterrupted ORF. Although transcripts of both parts are edited, no "trans-spliced" transcripts spanning both parts of the split ORF, that could be translated into a full sized protein product, were detected. Moreover, an antiserum directed against the product of t
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.35012 |
| Date | January 1998 |
| Creators | Menassa, Rima. |
| Contributors | Brown, Gregory G. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001641749, proquestno: NQ44513, Theses scanned by UMI/ProQuest. |
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