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Title: Cloning of cDNAs for glyoxysomal malate dehydrogenase and for phosphoenolpyruvate carboxykinase of cucumber (Cucumis sativus L.) and gene expression in cotyledons during development
Author: Kim, Dae-Jae
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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In higher plants a massive conversion of the storage lipid to carbohydrate takes place in germinating seedlings. The conversion involves β-oxidation, the glyoxylate cycle and gluconeogenesis. The key glyoxylate cycle enzymes isocitrate lyase (ICL) and malate synthase (MS) are co-ordinately synthesised to high levels during germination and decline thereafter to undetectable levels. The enzymes reappear at the final stage of the growth, in senescent tissues. In this study the synthesis of other enzymes involved in the conversion of lipid to carbohydrate was investigated to determine if they are co-ordinately synthesised with ICL and MS, and whether the genes encoding them are subject to the same control of expression. Full length cDNA clones encoding glyoxysomal malate dehydrogenase (gMDH) and phosphoenolpyruvate carboxykinase (PEPCK) have been isolated from a Cucumis sativus senescent cotyledon cDNA library. gMDH is one of the glyoxylate cycle enzymes, and PEPCK is a key enzyme for gluconeogenesis, which had not previously been cloned from plants. The cDNA and predicted amino acid sequence of gMDH show very high homology (94% and 97% respectively) with watermelon counterparts. The amino acid sequence deduced from the cDNA encoding PEPCK shows 43 to 57% identity with bacterial, yeast and trypanosome enzymes, and includes a conserved ATP-binding domain. The sequence of a full length cDNA predicts a polypeptide of 74,397 Da. The cDNA was expressed in Escherichia coli and antibodies raised to the resultant protein. The cucumber genome was shown to contain single genes encoding gMDH and PEPCK, the expression of which was investigated by northern and western blotting.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available