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Manipulation of pyrophosphate fructose 6-phosphate 1-phosphotransferase activity in sugarcane
Thesis (PhD (Genetics. Plant Biotechnology))--University of Stellenbosch, 2006.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : University of Stellenbosch
2006
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| _version_ | 1867613892456218624 |
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| access_status_str | Open Access |
| author | Groenewald, Jan-Hendrik |
| author2 | Botha, F. C. |
| author_browse | Botha, F. C. Groenewald, Jan-Hendrik |
| author_facet | Botha, F. C. Groenewald, Jan-Hendrik |
| author_sort | Groenewald, Jan-Hendrik |
| collection | Thesis |
| dc_rights_str_mv | University of Stellenbosch |
| description | Thesis (PhD (Genetics. Plant Biotechnology))--University of Stellenbosch, 2006. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/1089 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:43:21.794Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2006 |
| publishDateRange | 2006 |
| publishDateSort | 2006 |
| publisher | Stellenbosch : University of Stellenbosch |
| publisherStr | Stellenbosch : University of Stellenbosch |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/1089 Manipulation of pyrophosphate fructose 6-phosphate 1-phosphotransferase activity in sugarcane Groenewald, Jan-Hendrik Botha, F. C. University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics. Institute for Plant Biotechnology (IPB) Dissertations -- Plant biotechnology Theses -- Plant biotechnology Sugarcane -- Biotechnology Pyrophosphates Sugarcane -- Genetic engineering Thesis (PhD (Genetics. Plant Biotechnology))--University of Stellenbosch, 2006. The main aim of the work presented in this thesis was to elucidate the apparent role of pyrophosphate fructose 6-phosphate 1-phosphotransferase (PFP) in sucrose accumulation in sugarcane. PFP activity in sugarcane internodal tissue is inversely correlated to the sucrose content and positively to the water-insoluble component across varieties which differ in their capacities to accumulate sucrose. This apparent well defined and important role of PFP seems to stand in contrast to the ambiguity regarding PFP’s role in the general literature as well as the results of various transgenic studies where neither the downregulation nor the over-expression of PFP activity had a major influence on the phenotype of transgenic potato and tobacco plants. Based on this it was therefore thought that either the kinetic properties of sugarcane PFP is significantly different than that of other plant PFPs or that PFP’s role in sucrose accumulating tissues is different from that in starch accumulating tissues. In the first part of the study sugarcane PFP was therefore purified and its molecular and kinetic properties were determined. It consisted of two subunits which aggregated in dimeric, tetrameric and octameric forms depending on the presence of Fru 2,6-P2. Both the glycolytic and gluconeogenic reactions had broad pH optima and the kinetic parameters for all the substrates were comparable to that of other plant PFPs. The conclusion was therefore that sugarcane PFP’s molecular and kinetic characteristics do not differ significantly from that of other plant PFPs. The only direct way to confirm if PFP is involved in sucrose accumulation in sugarcane is to alter its levels in the same genetic background through genetic engineering. This was therefore the second focus of this study. PFP activity was successfully down-regulated in sugarcane. The transgenic plants showed no visible phenotype under greenhouse and field conditions and sucrose concentrations in their immature internodes were significantly increased. PFP activity was inversely correlated with sucrose content in the immature internodes of the transgenic lines. Both the immature and mature internodes of the transgenic plants had significantly higher fibre contents. This study suggests that PFP plays a significant role in glycolytic carbon flux in immature, metabolically active sugarcane internodal tissues. The data presented here confirm that PFP can indeed have an influence on the rate of glycolysis and carbon partitioning in these tissues. It also implies that there are no differences between the functions of PFP in starch and sucrose storing tissues and it supports the hypothesis that PFP provides additional glycolytic capacity to PFK at times of high metabolic flux in biosynthetically active tissue. This work will serve as a basis to refine future genetic manipulation strategies and could make a valuable contribution to the productivity of South African sugarcane varieties. Doctoral 2006-10-11T06:46:10Z 2010-06-01T08:12:13Z 2006-10-11T06:46:10Z 2010-06-01T08:12:13Z 2006-03 Thesis http://hdl.handle.net/10019.1/1089 en University of Stellenbosch 882248 bytes application/pdf application/pdf Stellenbosch : University of Stellenbosch |
| spellingShingle | Dissertations -- Plant biotechnology Theses -- Plant biotechnology Sugarcane -- Biotechnology Pyrophosphates Sugarcane -- Genetic engineering Groenewald, Jan-Hendrik Manipulation of pyrophosphate fructose 6-phosphate 1-phosphotransferase activity in sugarcane |
| title | Manipulation of pyrophosphate fructose 6-phosphate 1-phosphotransferase activity in sugarcane |
| title_full | Manipulation of pyrophosphate fructose 6-phosphate 1-phosphotransferase activity in sugarcane |
| title_fullStr | Manipulation of pyrophosphate fructose 6-phosphate 1-phosphotransferase activity in sugarcane |
| title_full_unstemmed | Manipulation of pyrophosphate fructose 6-phosphate 1-phosphotransferase activity in sugarcane |
| title_short | Manipulation of pyrophosphate fructose 6-phosphate 1-phosphotransferase activity in sugarcane |
| title_sort | manipulation of pyrophosphate fructose 6 phosphate 1 phosphotransferase activity in sugarcane |
| topic | Dissertations -- Plant biotechnology Theses -- Plant biotechnology Sugarcane -- Biotechnology Pyrophosphates Sugarcane -- Genetic engineering |
| url | http://hdl.handle.net/10019.1/1089 |
| work_keys_str_mv | AT groenewaldjanhendrik manipulationofpyrophosphatefructose6phosphate1phosphotransferaseactivityinsugarcane |