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However, previous work at JHI additionally suggests reduced respiratory capacity in potato tubers after long term storage caused by oxidative damage to mitochondria.
The aim of the studentship is to elucidate the key mechanisms resulting in senescent sugar accumulation and to identify genes that may underlie variation in the trait. Metabolic processes associated with senescent sweetening Tubers of up to four different cultivars will be stored with sprout suppressants under standard industry conditions for up to 12 months and dry matter, sugar and starch content monitored.
At present, little is known regarding the mechanisms of sugar accumulation, the genes underlying the senescent sweetening trait or the pre- and post-harvest factors that promote it.
Aims/Objectives A number of hypotheses regarding mechanisms of senescent sweetening have been previously proposed including i) oxidative damage to the amyloplast membrane resulting in exposure of starch granules to amylolytic enzymes  and ii) increased respiratory demand for repair of oxidative damage in stored tubers triggering starch degradation .
Lyophilised material will be archived for subsequent analyses of the tuber metabolome using standard GC/MS procedures  and metabolite fluxes will be estimated following labelling with [U-13C]glucose.
Activities of enzymes associated with key flux control points will be estimated using standard assays. Transcriptome changes associated with senescent sweetening RNA will be extracted from lyophilized archived material at appropriate stages in sweetening development and subject to microarray transcriptome analysis.
Levels and redox status of the key redox buffers (ascorbate, glutathione, NAD(P)) will be monitored using a spectrophotometric plate method.
However, treatment of cells with EGCG results in production of hydrogen peroxide and hydroxyl radicals in the presence of Fe (III).
Thus, EGCG functions as a pro-oxidant in some cellular contexts.
Green tea is rich in polyphenol flavonoids including catechins.
Epigallocatechin 3-gallate (EGCG) is the most abundant and potent green tea catechin.