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Expression of a single gene
encoding microbody NAD-malate dehydrogenase during glyoxysome and
peroxisome development in cucumber.
Kim DJ, Smith
SM.
Institute of Cell and Molecular Biology, University of
Edinburgh, UK.
A full-length cDNA clone encoding microbody
NAD(+)-dependent malate dehydrogenase (MDH) of cucumber has been
isolated. The deduced amino acid sequence is 97% identical to
glyoxysomal MDH (gMDH) of watermelon, including the amino terminal
putative transit peptide. The cucumber genome contains only a single
copy of this gene. Expression of this mdh gene increases dramatically in
cotyledons during the few days immediately following seed imbibition, in
parallel with genes encoding isocitrate lyase (ICL) and malate synthase
(MS), two glyoxylate cycle enzymes. The level of MDH, ICL and MS mRNAs
then declines, but then MDH mRNA increases again together with that of
peroxisomal NAD(+)-dependent hydroxypyruvate reductase (HPR). The mdh
gene is also expressed during cotyledon senescence, together with hpr,
icl and ms genes. These results indicate that a single gene encodes MDH
which functions in both glyoxysomes and peroxisomes. In contrast to icl
and ms genes, expression of the mdh gene is not activated by incubating
detached green cotyledons in the dark, nor is it affected by exogenous
sucrose in the incubation medium. The function of this microbody MDH and
the regulation of its synthesis are discussed.
PMID: 7858221
[PubMed - indexed for MEDLINE]
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