Plant Physiol, October 2001, Vol. 127, pp. 615-623
Characterization of Two cDNAs Encoding Mitochondrial Lipoamide
Dehydrogenase from Arabidopsis1
Isabelle
Lutziger and
David J.
Oliver*
353 Bessey Hall, Department of Botany, Iowa State University, Ames,
Iowa 50011-1020
In contrast to peas (Pisum sativum), where
mitochondrial lipoamide dehydrogenase is encoded by a single gene and
shared between the 
-ketoacid dehydrogenase complexes and the Gly
decarboxylase complex, Arabidopsis has two genes encoding for two
mitochondrial lipoamide dehydrogenases. Northern-blot analysis revealed
different levels of RNA expression for the two genes in different
organs; mtLPD1 had higher RNA levels in green leaves
compared with the much lower level in roots. The mRNA for
mtLPD2 shows the inverse pattern. The other organs
examined showed nearly equal RNA expressions for both genes. Analysis
of etiolated seedlings transferred to light showed a strong induction
of RNA expression for mtLPD1 but only a moderate
induction of mtLPD2. Based on the organ and
light-dependent expression patterns, we hypothesize that
mtLPD1 encodes the protein most often associated with
the Gly decarboxylase complex, and mtLPD2 encodes the
protein incorporated into -ketoacid dehydrogenase complexes. Due to
the high level of sequence conservation between the two mtLPDs, we
assume that the proteins, once in the mitochondrial matrix, are
interchangeable among the different multienzyme complexes. If present
at high levels, one mtLPD might substitute for the other. Supporting
this hypothesis are results obtained with a T-DNA knockout mutant,
mtlpd2, which shows no apparent phenotypic change under
laboratory growth conditions. This indicates that mtLPD1 can substitute
for mtLPD2 and associate with all these multienzyme complexes.
1
This research was supported by the U.S.
Department of Agriculture National Research Initiative Competitive
Grants Office and is a publication of the Iowa Agricultural Experiment Station.
*
Corresponding author; e-mail doliver{at}iastate.edu; fax
515-294-1337.
© 2001 American Society of Plant Physiologists
