In this study potato plant with lowered D-enzyme activity were investigated. It was found previously that lack of D-enzyme resulted in a reduction in the tuber yield of these plants and a delay in tuber sprouting. In this study the reduction in tuber yield was characterised further. It was found that tuber fresh weight per plant was reduced but percentage dry matter and starch content were unaltered. In addition, the extent of the reduction in fresh weight tuber yield was dependent on irradiance. Lack of D-enzyme also resulted in a delay in sugar accumulation in tuber during prolonged storage. No differences were detected in the rates of starch synthesis and starch turnover in tubers with lowered D-enzyme activity compared to controls. One reason for this could have been that the labelling experiments employed to investigate tuber metabolism were not sensitive enough to detect small differences. To address this, D-enzyme activity was lowered in transgenic potato plants which exhibit exaggerated rates of starch synthesis and turnover due to the expression of a heterologous ADPglucose pyrophosphorylase gene. It was hypothesised that differences in starch metabolism would be more likely to be resolved in tubers from these plants. Surprisingly, no appreciable differences between the starch metabolism of tubers with exaggerated rates of starch turnover and lowered D-enzyme activity and control tubers were detected. However, the level of D-enzyme activity in these tubers was 14% of wild type and this could have been high enough for the <i>in vivo</i> role(s) of the enzyme to be fulfilled. Rates of starch breakdown in leaf tissue lacking D-enzyme were slightly reduced compared to controls during darkness. Lack of D-enzyme did not affect rates of starch synthesis during the light. These results are consistent with those from the D-enzyme mutant of <i>A. thaliana</i> and suggest that D-enzyme may have a role in potato leaf starch degradation during darkness and that this could in turn influence tuber growth.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:662227 |
| Date | January 2000 |
| Creators | Snow, Juliette Elizabeth |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/11421 |
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