Show simple item record

dc.contributor.advisorKaminskyj, Susan G. W.en_US
dc.creatorYang, Yien_US
dc.date.accessioned2003-07-16T20:56:45Zen_US
dc.date.accessioned2013-01-04T04:45:02Z
dc.date.available2004-09-03T08:00:00Zen_US
dc.date.available2013-01-04T04:45:02Z
dc.date.created2003-08en_US
dc.date.issued2003-08-12en_US
dc.date.submittedAugust 2003en_US
dc.identifier.urihttp://hdl.handle.net/10388/etd-07162003-205645en_US
dc.description.abstractThis study aimed to identify the genetic basis of the Aspergillus nidulans hypB5 mutant phenotype. A. nidulans is a filamentous fungus that is widely used as a cell biological and molecular genetic model system. Its hyphae grow by localized polar secretion, producing tubular cells. A. nidulans hypercellular strains define five unlinked genes, hypA1-hypE2, which cause hyphal morphogenesis defects at 42°C. hypA is orthologous to Saccharomyces TRS120, which mediates Golgi transit and is widely conserved. The hypB5 restrictive phenotype resembles hypA1: wide hyphae, short basal cells and small nuclei. Like hypA1, shifting hypB5 mutants from 28°C to 42°C causes cessation of tip growth but isotropic expansion of basal cells. A hypA1, hypB5 double mutant was impaired for growth at 28°C, suggesting these genes have related roles, but neither was epistatic at 37°C so they function in different pathways. The A. nidulans pRG3-AMA1 genomic library was used to clone hypB5 complementing DNA by phenotype rescue, and subcloned to a 5 kb KpnI fragment, pYY2. pYY2 was disrupted and sequenced by Tn1000 insertional mutagenesis. The pYY2 sequence is 4975 bp and encodes a putative Sec7 domain which has 81% identity to the Saccharomyces SEC7 domain. The Sec7 domain is highly conserved from yeasts to mammals. Saccharomyces SEC7 encodes a guanine nucleotide exchange factor involved in COPI vesicle formation and Golgi biogenesis. Insertions in the pYY2 non-Sec7 domain coding region complemented hypB5 efficiently, whereas those in the Sec7 domain did not, indicating that the Sec7 domain is sufficient for function. A point mutation was found in the hypB5 strain Sec7 domain, which could explain temperature sensitivity. However, the pYY2 sequence is found on chromosome I whereas hypB maps to chromosome VII. Although the origin and functional role of the point mutation in the hypB5 strain Sec7 protein remains unresolved, it appears that pYY2 contains an extragenic suppressor. Thus hypB likely encodes an element in the COPI vesicle assembly pathway.en_US
dc.language.isoen_USen_US
dc.subjecthyphaeen_US
dc.subjectmorphogenesisen_US
dc.subjectSec7en_US
dc.subjectendomembraneen_US
dc.subjecthypBen_US
dc.subjectAspergillus nidulansen_US
dc.titleCloning and analysis of an Aspergillus nidulans Sec7 domain coding geneen_US
thesis.degree.departmentBiologyen_US
thesis.degree.disciplineBiologyen_US
thesis.degree.grantorUniversity of Saskatchewanen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Science (M.Sc.)en_US
dc.type.materialtexten_US
dc.type.genreThesisen_US
dc.contributor.committeeMemberFowke, Larry C.en_US
dc.contributor.committeeMemberWei, Yangdouen_US


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record