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Molecular cloning of cucumber phosphoenolpyruvate carboxykinase and developmental regulation of gene expression


Kim, D-J and Smith, SM, Molecular cloning of cucumber phosphoenolpyruvate carboxykinase and developmental regulation of gene expression, Plant Molecular Biology, 26, (1) pp. 423-434. ISSN 0167-4412 (1994) [Refereed Article]

Copyright Statement

Copyright 1994 Kluwer Academic Publishers

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DOI: doi:10.1007/BF00039551


A cDNA library from RNA of senescing cucumber cotyledons was screened for sequences also expressed in cotyledons during post-germinative growth. One clone encodes ATP-dependent phosphoenolpyruvate carboxykinase (PCK; EC, an enzyme of the gluconeogenic pathway. The sequence of a fulllength cDNA predicts a polypeptide of 74 397 Da which is 43 Yo, 49~o and 57~o identical to bacterial, trypanosome and yeast enzymes, respectively. The cDNA was expressed in Escherichia coli and antibodies raised against the resultant protein. The antibody recognises a single polypeptide of ca. 74 kDa, in extracts of cotyledons, leaves and roots. The cucumber genome contains a single pck gene. In the seven-day period after seed imbibition, PCK mRNA and protein steady-state levels increase in amount in cotyledons, peaking at days 2 and 3 respectively, and then decrease. Both accumulate again to a low level in senescing cotyledons. This pattern of gene expression is similar to that of isocitrate lyase (ICL) and malate synthase (MS). When green cotyledons are detached from seedlings and incubated in the dark, ICL and MS mRNAs increase rapidly in amount but PCK mRNA does not. Therefore it seems unlikely that the glyoxylate cycle serves primarily a gluconeogenic role in starved (detached) cotyledons, in contrast to post-germinative and senescing cotyledons where PCK, ICL and MS are coordinately synthesised. While exogenous sucrose greatly represses expression of icl and ms genes in dark-incubated cotyledons, it has a smaller effect on the level of PCK mRNA.

Item Details

Item Type:Refereed Article
Keywords:cucumber, Cucumis sativus, germination, gluconeogenesis, phosphoenolpyruvate carboxykinase, senescence
Research Division:Biological Sciences
Research Group:Plant biology
Research Field:Plant physiology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the biological sciences
UTAS Author:Smith, SM (Professor Steven Smith)
ID Code:101589
Year Published:1994
Web of Science® Times Cited:59
Deposited By:Plant Science
Deposited On:2015-06-26
Last Modified:2015-09-21

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