Analysis of intermediate carbon metabolism in strawberry plants

Simple item page
dc.contributor.advisorGroenewald, J.-H.en_ZA
dc.contributor.advisorBauer, R.en_ZA
dc.contributor.authorBasson, Carin Elizabethen_ZA
dc.contributor.otherStellenbosch University. Faculty of AgriSciences. Dept. of Genetics. Institute for Plant Biotechnology.
dc.date.accessioned2008-11-24T09:50:35Zen_ZA
dc.date.accessioned2010-06-01T08:45:23Z
dc.date.available2008-11-24T09:50:35Zen_ZA
dc.date.available2010-06-01T08:45:23Z
dc.date.issued2008-12
dc.descriptionThesis (MSc (Genetics. Institute for Plant Biotechnology)--Stellenbosch University, 2008.
dc.description.abstractStrawberry (Fragaria x ananassa) fruit quality is largely determined by the relative amounts of sugars and organic acids present, as well as soluble solid content. This study had three components: 1) Characterisation of cytosolic carbohydrate metabolism and carbon partitioning to sugars and organic acids in two commercial varieties, 2) analysis of transgenic strawberry fruit with increased pyrophosphate: D-fructose-6-phosphate 1-phosphotransferase (PFP) activity and 3) analysis of transgenic strawberry fruit with increased ß-fructosidase (invertase) activity in either cytosol or apoplast. Analyses of transgenic strawberry may inform similar attempts in grape berries. Festival and Ventana, two popular commercial strawberry cultivars in South Africa, were fairly similar with respect to sugar and organic acid content. Twelve cytosolic enzymes were investigated. Temporal differences in maximum catalytic activity were observed for invertase, PFP, pyruvate kinase and ADP-glucose pyrophosphorylase (AGPase). Invertase, PFP and AGPase activity also differed between the cultivars. One enzyme, SuSy, could not be analysed effectively, due to the purification method employed. These analyses established methodology for the analysis of transgenic berries. Constructs were designed to constituitively express Giardia lamblia PFP (GL-PFP), or to express Saccharomyces cerevisiae invertase (SCI) in a fruit-specific manner. A second invertase construct was designed to target SCI to the apoplast. Strawberry (cv. Selekta) was transformed and the presence of each transgene confirmed by PCR. Untransformed Selekta was used as control in both transgenic studies. Transgenic lines were selected based on GL-PFP activity in leaves and total PFP activity in ripe fruit. Sugar and organic acid content of ripe berries with high PFP activity was determined. Although berries displayed marked changes in sugar composition, the total sugar content was similar to controls, in all except one line. Organic acid content was decreased, leading to a clear reduction in organic acid-to-sugar ratio. This points to a gluconeogenic role for PFP in strawberry fruit. Transgenic berries were screened for SCI activity. Berries containing untargeted SCI exhibited total invertase activity similar to controls and were not analysed further. Berries with apoplasttargeted SCI displayed three-fold increases in invertase activity compared to controls. Total sugar content was reduced and exhibited reduced sucrose content relative to hexoses. Despite the effect of increased invertase activity on metabolites, maximum catalytic activity of enzymes involved in cytosolic sucrose, hexose and organic acid metabolism were unchanged. Transgenic plants selected in these studies were subsequently vegetatively replicated and future work will include immature fruit.en_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/2295
dc.language.isoenen_ZA
dc.publisherStellenbosch : Stellenbosch University
dc.rights.holderStellenbosch University
dc.subjectCarbon metabolism of strawberriesen_ZA
dc.subjectBiotechnologyen_ZA
dc.subjectPyrophosphateen_ZA
dc.subjectCarbon partitioning in plantsen_ZA
dc.subjectTheses -- Plant biotechnologyen_ZA
dc.subjectDissertations -- Plant biotechnologyen_ZA
dc.subject.lcshStrawberries -- Metabolismen-ZA
dc.subject.otherGeneticsen_ZA
dc.subject.otherInstitute for Plant Biotechnologyen_ZA
dc.titleAnalysis of intermediate carbon metabolism in strawberry plantsen_ZA
dc.typeThesisen_ZA
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
basson_analysis_2008.pdf
Size:
560.35 KB
Format:
Adobe Portable Document Format
Description:
Download
Collections
Masters Degrees (Genetics)