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Temperature-dependent Regulation of Sugar Metabolism During Cold Stress Responses
Zhao, Lu
2017, Doctor of Philosophy, Ohio State University, Horticulture and Crop Science.
Many plant crops of temperate origins, particularly those that overwinter in the field, are sensitive to cold temperatures. Following exposure to low temperatures, cold-sensitive crops experience disruptions to physiological process and cellular architectures, ultimately resulting in chilling and/or freeze injuries. In order to survive harsh winter, cold-tolerant plants have improved their freezing tolerance (FT) by undergoing a complex series of developmental processes as known as “cold acclimation”, following a period of exposure to low but non-freezing temperatures. As part of the acclimation responses, plants accumulated sugars in a tissue-specific fashion. These sugars have been proposed to play a role in mediating plant FT by serving as cryoprotectants, stabilizing the plasma membrane and/or depressing the cytosolic freezing point. To increase our understanding of the role of sugar metabolism and accumulation during cold stress responses, we have taken a metabolomics and molecular biology-based approach. To monitor the cold-induced changes in sugar levels during the cold acclimation process, an optimized capillary zone electrophoresis (CZE) method was developed and was used to separate and quantify mono-, di-, and oligosaccharides isolated from plant tissues. The optimized CZE method provides an average limit-of-detection (LOD) of 1.5 ng/µL for individual carbohydrates, with comparable or superior to the average LOD for these sugars using gas chromatography-mass spectrometry. This optimized CZE method was used to metabolically profile cold-induced shifts in sugar accumulation in two plant species (rubber-producing dandelions and grapevines), as well as to investigate the effect of ABA treatment on sugar accumulation during the development of FT. In addition to mono-, di-, and tri-saccharides, in studies using dandelions, we also monitored the accumulation of inulin. Inulin is a fructose polymer found in the storage organs of rubber-producing dandelions such as Taraxacum kok-saghyz (TK) and Taraxacum brevicorniculatum (TB). The sugar levels in TB roots were quantified following ambient or cold treatment using our CZE method. Our data indicated that exposure to cold increases the accumulation of mono-, di-, and inulin-type oligosaccharides in TB roots. Finally, based on our metabolomics data, we initiated a study to metabolically engineer increased cold tolerance in grapes by increasing the synthesis of raffinose family oligosaccharides (RFOs). In this work, the key enzymes in the synthetic pathway of RFOs, galactinol synthase and raffinose synthase were introduced into grape calli via particle bombardment. The transgenic grape calli obtained through this work will be used to generate transgenic grapevines for future FT analysis. In grapes, our data indicated that cold acclimation increased the accumulation of RFOs, confirming previously published studies. Overall, the work presented in this dissertation increases our knowledge of the regulatory roles of cold and hormone stresses on plant carbohydrate accumulation, and will help design strategies to manipulate carbon allocation in metabolic analysis and improve economic sustainability of rubber-producing dandelions and grapes.
Joshua Blakeslee (Advisor)
Katrina Cornish (Advisor)
Imed Dami (Committee Member)
Feng Qu (Committee Member)
240 p.

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Zhao, L. (2017). Temperature-dependent Regulation of Sugar Metabolism During Cold Stress Responses. (Electronic Thesis or Dissertation). Retrieved from https://etd.ohiolink.edu/

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Zhao, Lu. "Temperature-dependent Regulation of Sugar Metabolism During Cold Stress Responses." Electronic Thesis or Dissertation. Ohio State University, 2017. OhioLINK Electronic Theses and Dissertations Center. 09 Jul 2017.

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Zhao, Lu "Temperature-dependent Regulation of Sugar Metabolism During Cold Stress Responses." Electronic Thesis or Dissertation. Ohio State University, 2017. https://etd.ohiolink.edu/

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Full text release has been delayed at the author's request until May 07, 2022
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