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Developmental expression of the mitochondrial pyruvate dehydrogenase complex in pea ( Pisum sativum ) seedlings
Author(s) -
Luethy Michael H.,
Gemel Joanna,
Johnston Mark L.,
Mooney Brian P.,
Miernyk Jan A.,
Randall Douglas D.
Publication year - 2001
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2001.1120414.x
Subject(s) - pisum , biology , sativum , pyruvate dehydrogenase complex , photorespiration , protein subunit , biochemistry , dehydrogenase , glycine , photosynthesis , microbiology and biotechnology , botany , enzyme , gene , amino acid
In order to better understand control of the mitochondrial pyruvate dehydrogenase complex (PDC), total catalytic activity was determined during development of the primary leaves of pea ( Pisum sativum L.) seedlings, as well as in each leaf pair of 21‐day‐old plants. Activity of the PDC in clarified homogenates was highest in the youngest organs and then dropped dramatically as the leaves matured and became photosynthetically competent. As leaves began to senesce, total PDC activity dropped to zero. Steady‐state mRNA levels were determined using E1 and E3 cDNA probes. The overall pattern of transcript abundance matched the pattern observed for total PDC activity; transcript levels for E1 α and E1 β approached zero during senescence. Levels of the E1 α , E1 β , E2 and E3 subunits of the PDC were analyzed in the same samples, using specific antibodies. Quantitation of the immunoblotting results throughout this developmental series showed a pattern in parallel with that of catalytic activity and mRNA levels, although the relative changes in subunit protein levels were not as extreme as the changes in activity. The exception to the global pattern was that of the E3 subunit: lipoamide dehydrogenase. Expression of this enzyme was highest in mature, fully expanded leaves, which were active in photosynthesis and photorespiration, reflecting the additional role of E3 as a component of glycine decarboxylase.