The analysis and reduction of starch in sugarcane by silencing ADP-glucose pyrophosphorylase and over-expressing β-amylase

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dc.contributor.advisor Groenewald, J-H.
dc.contributor.advisor Lloyd, J. R.
dc.contributor.author Ferreira, Stephanus Johannes
dc.date.accessioned 2008-03-26T12:07:17Z en_ZA
dc.date.accessioned 2010-06-01T09:00:44Z
dc.date.available 2008-03-26T12:07:17Z en_ZA
dc.date.available 2010-06-01T09:00:44Z
dc.date.issued 2007-12
dc.identifier.uri http://hdl.handle.net/10019.1/2880
dc.description Thesis (MSc (Plant Biotechnology))--University of Stellenbosch, 2007.
dc.description.abstract Sugarcane is cultivated because of the high levels of sucrose it stores in its internodes. Starch metabolism has been a neglected aspect of sugarcane research despite the problems caused by it during sugarcane processing. Currently there is no information available on the starch content in different South African commercial sugarcane varieties. This project had two main aims of which the first was to determine the starch content in the internodal tissues of six commercial sugarcane varieties. The activities of ADP-Glucose Pyrophosphorylase (AGPase) and β- amylase were also determined. The second aim of the project was to manipulate starch metabolism in sugarcane using transgenesis. To achieve this, transformation vectors for the down-regulation of AGPase activity and over-expression of β-amylase activity were designed. These vectors were then used to transform sugarcane calli and the results were analysed in suspension cultures. Starch levels in sugarcane internodal tissue increased more than 4 times from young to mature internodes. There were also large differences between varieties. When mature tissues of different varieties were compared, their starch concentration varied between 0.18 and 0.51 mg g-1 FW, with the majority of the varieties having a starch concentration between 0.26 and 0.32 mg g-1 FW. NCo376’s starch concentration was much lower than the rest at 0.18 mg g-1 FW and N19’s was much higher at 0.51 mg. g-1 FW. There was also a very strong correlation between starch and sucrose concentration (R2 = 0.53, p ≤ 0.01) which could be due to the fact that these metabolites are synthesized from the same hexose-phosphate pool. No correlation was evident between starch concentration and AGPase activity. This was true for correlations based on either tissue maturity or variety. β-amylase activity expressed on a protein basis was almost 5 times higher in the young internodes compared to mature internodes, suggesting that carbon might be cycled through starch in these internodes. AGPase activity in the transgenic suspension cultures was reduced by between 0.14 and 0.54 of the activity of the wild type control. This reduction led to a reduction in starch concentration of between 0.38 and 0.47 times that of the wild type control. There was a significant correlation between the reduction in AGPase activity and the reduction in starch (R2 = 0.58, p ≤ 0.05). β-amylase activity in the transgenic suspension cultures was increased to 1.5-2 times that of the wild type control. This led to a reduction in starch concentration of between 0.1 and 0.4 times that of the wild type control. Once again the increase in β-amylase activity could be correlated to the reduction in starch concentration of the transgenic suspension cultures (R2 = 0.68, p ≤ 0.01). In both experiments there was no significant effect on sucrose concentration. en
dc.format.extent 825429 bytes en_ZA
dc.format.mimetype application/pdf en_ZA
dc.language.iso en
dc.publisher Stellenbosch : University of Stellenbosch
dc.subject Sugarcane en
dc.subject ADP-Glucose pyrophosphorylase en
dc.subject Beta amylase en
dc.subject Dissertations -- Plant biotechnology en
dc.subject Theses -- Plant biotechnology en
dc.subject Sugarcane -- Biotechnology en
dc.subject Starch -- Synthesis en
dc.subject ADP-glucose pyrophosphorylase
dc.subject β-amylase en
dc.title The analysis and reduction of starch in sugarcane by silencing ADP-glucose pyrophosphorylase and over-expressing β-amylase en
dc.type Thesis
dc.rights.holder University of Stellenbosch


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