Gibberellin regulates mitochondrial pyruvate dehydrogenase activity in rice.
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 microM 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 beta-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.
Jan
Asad
A
National Institute of Agrobiological Sciences, Tsukuba, 305-8602 Japan.
Nakamura
Hidemitsu
H
Handa
Hirokazu
H
Ichikawa
Hiroaki
H
Matsumoto
Hiroshi
H
Komatsu
Setsuko
S
D015152:Blotting, Northern; D003001:Cloning, Molecular; D004789:Enzyme Activation; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D017343:Genes, Plant; D005875:Gibberellins / Q000494:pharmacology* / Q000502:physiology; D005966:Glucuronidase / Q000235:genetics; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology*; D020411:Oligonucleotide Array Sequence Analysis; D012275:Oryza / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D018515:Plant Leaves / Q000201:enzymology; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D005875:Gibberellins; D007527:Isoenzymes; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011768:Pyruvate Dehydrogenase Complex; D011993:Recombinant Fusion Proteins; C007842:gibberellic acid; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D005966:Glucuronidase