Show simple item record

dc.contributor.advisorKock, J. L. F.
dc.contributor.authorLeeuw, Ntsoaki Joyce
dc.contributor.otherPohl, C. H.
dc.contributor.otherVan Wyk, P. W. J.
dc.date.accessioned2015-09-08T08:37:56Z
dc.date.available2015-09-08T08:37:56Z
dc.date.copyright2006-11
dc.date.issued2006-11
dc.date.submitted2006-11
dc.identifier.urihttp://hdl.handle.net/11660/1186
dc.description.abstractEnglish: In the early 1990’s, Kock and co-workers discovered acetylsalicylic acid (ASA)-sensitive oxylipins in yeasts. It was also reported that the site of production of these compounds may serve as important targets to control fungal infections. In 2004, researchers exposed another function for these oxylipins – they may act as lubricants during spore release from enclosed asci. Since oxylipin production in only a limited number of species representing Eremothecium was thus far studied, it became the aim of this project to further extend this study and to determine the type and distribution of 3- hydroxy (OH) oxylipins in the remaining species i.e. Eremothecium coryli, E. cymbalariae and E. gossypii. In addition, the possible functions of these oxylipins as well as ascospore shape and ornamentations were assessed. Finally, the antifungal activity of ASA was also investigated in this group of important plant pathogens as well as other yeasts. Eremothecium coryli is known to produce intriguing spindle-shaped ascospores with long and thin whip-like appendages. In this study, ultra structural studies using scanning electron microscopy, indicate that these appendages serve to coil around themselves and around ascospores causing spore aggregation. Furthermore, using immunofluoresence confocal laser scanning microscopy it was found that hydrophobic 3-OH oxylipins cover the surfaces of these ascospores. Using gas chromatography-mass spectrometry, only the oxylipin 3-OH 9:1 (a monounsaturated fatty acid consisting of a hydroxyl group on carbon 3) could be identified. Sequential digital imaging suggests that oxylipin-coated spindle-shaped ascospores are released from enclosed asci probably by protruding through an already disintegrating ascus wall. Using immunofluorescence microscopy and 3-OH oxylipin specific antibodies, it was possible to map the presence of these compounds also in other Eremothecium species. In E. cymbalariae, these oxylipins were found to cover mostly the spiky tips of narrowly triangular ascospores while in E. gossypii, oxylipins covered the whole spindle-shaped ascospore with terminal appendages. The presence of these oxylipins was confirmed by chemical analysis. When ASA, a 3-OH oxylipin inhibitor, was added to these yeasts in increasing concentrations, the sexual stage was found to be the most sensitive. Results suggest that 3-OH oxylipins, produced by mitochondria through incomplete β-oxidation, are associated with the development of the sexual stages in both yeasts. Strikingly, preliminary studies on yeast growth suggest that yeasts, characterized by mainly an aerobic respiration rather than a fermentative pathway, are more sensitive to ASA than yeasts characterized by both pathways. These data further support the role of mitochondria in sexual as well as asexual reproduction of yeasts and its role to serve as target for ASA antifungal action.en_ZA
dc.description.abstractAfrikaans; Kock en medewerkers het gedurende die vroeë 1990’s asetielsalisiensuur (ASS)- sensitiewe oksielipiene in giste ontdek. Dit is ook gerapporteer dat die setel van produksie van hierdie verbindings as belangrike teiken vir die beheer van fungale infeksies mag dien. In 2004 het navorsers nog ‘n funksie van hierdie oksielipiene blootgelê – hulle mag as smeermiddels gedurende die vrystelling van spore dien vanuit geslote aski. Aangesien oksielipienproduksie sover slegs in ‘n paar spesies van die genus Eremothecium bestudeer is, het dit die doel van hierdie projek geword om die studie uit te brei en om die tipe en verspreiding van 3-hidroksie (OH)-oksielipiene in die oorblywende spesies d.i. Eremothecium coryli, E. cymbalariae en E. gossypii, te bepaal. Verder is die moontlike funksies van die oksielipiene asook die askospoorvorm en ornamentasie ondersoek. Laastens is die antifungale aktiwiteit van ASS in hierdie groep belangrike plantpatogene asook in ander giste bestudeer. Dit is bekend dat Eremothecium coryli fassinerende naaldvormige askospore met lang, sweepagtige aanhangsels produseer. In hierdie studie is d.m.v. skandeerelektronmikroskopie van die ultrastruktuur, aangetoon dat die aanhangsels om mekaar en om askospore draai, om spooraggregasie tot gevolg te hê. Verder is d.m.v. immunofluoreserende konfokale laserskandeermikroskopie gevind dat hidrofobiese 3-OH-oksielipiene die oppervlaktes van die askospore bedek. Met behulp van gaschromatografie-massaspektrometrie kon slegs die oksielipien, 3-OH 9:1 (‘n mono-onversadigde vetsuur met ‘n hidroksielgroep op koolstof 3) geïdentifiseer word. Opeenvolgende digitale uitbeelding dui dat oksielipienbedekte, naaldvormige askospore deur vooraf disintegrerende askuswande vrygestel word, moontlik d.m.v. turgordruk. Met behulp van immunofluoresensiemikroskopie en 3-OH-oksielipienspesifieke teenliggaampies was dit moontlik om die teenwoordigheid van hierdie verbindings ook in ander Eremothecium spesies te karteer. In E. cymbalariae, is gevind dat die oksielipiene die skerp punte van die smal driehoekige askospore bedek, terwyl in die geval van E. gossypii, die hele naaldvormige askospoor en terminale aanhangsel met 3-OH-oksielipiene bedek is. Die teenwoordigheid van hierdie oksielipiene is deur chemiese analise bevestig. Indien ASS, ‘n 3-OH-oksielipieninhibeerder, in toenemende konsentrasies by die gis gevoeg word, is gevind dat die seksuele stadium die sensitiefste is. Resultate dui daarop dat 3- OH-oksielipiene, wat deur die mitochondria deur onvolledige β-oksidasie gevorm word, met die ontwikkeling van die geslagtelike fase in albei van laasgenoemde giste geassosieer is. Voorlopige studies dui daarop dat giste, gekarakteriseer deur hoofsaakllik aerobiese respirasie eerder as fermentasie, meer sensitief is vir ASS as giste wat deur beide metaboliese weë gekenmerk word. Hierdie data ondersteun die rol van mitochondria in seksuele en aseksuele voortplanting verder, asook die rol as teiken vir ASS se antifungale werking.af
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectEremotheciumen_ZA
dc.subjectAscosporesen_ZA
dc.subjectAscomycetesen_ZA
dc.subjectAcetylsalicylic aciden_ZA
dc.subjectAntifungalen_ZA
dc.subjectAspirinen_ZA
dc.subjectConfocal laser scanning microscopyen_ZA
dc.subjectEremothecium corylien_ZA
dc.subjectEremothecium cymbalariaeen_ZA
dc.subjectEremothecium gossypiien_ZA
dc.subjectMitochondriaen_ZA
dc.subject3-Hydroxy oxylipinsen_ZA
dc.subjectDissertation (M.Sc. (Microbial, Biochemical and Food Biotechnology))--University of the Free State, 2006en_ZA
dc.titleOxylipin distribution in Eremotheciumen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record