PLANT PHYSIOLOGY , Vol 114, Issue 3 1021-1029, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Differential Induction of Pyruvate Decarboxylase Subunits and Transcripts in Anoxic Rice Seedlings
J. Rivoal, S. Thind, A. Pradet and B. Ricard
Station de Physiologie Vegetale, Institut Nationale de la Recherche Agronomique, Centre de Recherches de Bordeaux, BP 81, 33 883 Villenave d'Ornon, France
In 2-d-old rice (Oryza sativa L.) seedlings subjected to anoxic stress,
pyruvate decarboxylase (PDC) activity increased 9-fold during a 168-h
period. A polyclonal PDC antiserum that recognized [alpha]- and
[beta]-subunits was used to quantify PDC protein by an enzyme-linked
immunosorbant assay and showed a 5.6-fold increase, suggesting that the
anoxically induced enzyme has a higher specific activity than the PDC
isoform present under normoxia. Immunoblot analysis showed that levels of
both PDC subunits were induced by anoxia. Immunoprecipitation of proteins
labeled in vivo during anoxic treatment demonstrated that the
[alpha]-subunit was preferentially synthesized at the onset of anoxia Two
partial cDNAs, including a novel sequence, were cloned from a cDNA library
made from seedlings subjected to anoxia for 6 h. Gene-specific probes used
to quantify northern blots showed that two or three PDC mRNAs are
differentially induced by anoxia in rice seedlings. Immunoprecipitation of
in vitro translation products of mRNAs isolated at different times of
anoxic treatment confirmed this finding. Our results suggest that anoxic
induction of rice PDC involves transcriptional and posttranscriptional
regulation of gene expression as well as differences in enzyme
characteristics.
