Journal Article

Gibberellin Regulates Mitochondrial Pyruvate Dehydrogenase Activity in Rice

Asad Jan, Hidemitsu Nakamura, Hirokazu Handa, Hiroaki Ichikawa, Hiroshi Matsumoto and Setsuko Komatsu

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 47, issue 2, pages 244-253
Published in print February 2006 | ISSN: 0032-0781
Published online February 2006 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci241
Gibberellin Regulates Mitochondrial Pyruvate Dehydrogenase Activity in Rice

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Pyruvate dehydrogenase kinase (PDK) is a negative regulator of the mitochondrial pyruvate dehydrogenase complex (mtPDC) that plays a key role in intermediary metabolism. OsPDK1 was identified as a gibberellin-up-regulated gene using a cDNA microarray. The full-length cDNA for OsPDK1 was 1498 bp and encoded a predicted polypeptide of 363 amino acids. Genomic DNA analysis showed the presence of another isoform of PDK, OsPDK2, in rice. Reverse transcriptase–PCR analysis revealed differential expression of the two isoforms. OsPDK1 was expressed in leaf blade and leaf sheath but not in callus and root, while OsPDK2 was expressed constitutively in all tissues examined. Maximum expression of OsPDK1 in leaf sheath was detected by Northern blot analysis when seedlings were treated with 5 µM GA3 for 24 h. OsPDK1 expression was up-regulated by GA3, and there was little effect of other plant hormones. Mitochondrial pyruvate dehydrogenase (PDH) activity was reduced compared with control plants in 2-week-old seedlings treated with GA3. The β-glucuronidase (GUS) reporter gene, driven by a 2,067 bp OsPDK1 promoter region fragment, was mainly expressed in the aleurone layer of germinating seed and leaf sheath. Transgenic rice expressing PDK1 RNAi had altered vegetative growth with reduced accumulation of vegetative tissues. These results suggest that gibberellin modulates the activity of mtPDC by regulating OsPDK1 expression and subsequently controlling plant growth and development.

Keywords: Elongation; Gibberellin; Leaf sheath; Mitochondrial pyruvate dehydrogenase; Rice; Acs, acetyl-CoA synthetase; Adh, alcohol dehydrogenase; Aldh,acetaldehyde dehydrogenase; BA, 6-benzyladenine; BL, brassinolide; CaMV, cauliflower mosaic virus; GA3, gibberellic acid; GUS, β-glucuronidase; Pdc, pyruvate decarboxylase; PDC, pyruvate dehydrogenase complex; PDH, pyruvate dehydrogenase; PDK, pyruvate dehydrogenase kinase; PDP, pyruvate dehydrogenase phosphatase; PHK, protein histidine kinase; PPAR-α, peroxisome proliferator-activated receptor-α; RACE, rapid amplification of cDNA ends; RNAi, RNA interference; RT–PCR, reverse transcription–PCR; TCA, tricarboxylic acid; UTR, untranslated region

Journal Article.  6943 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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