Journal of Experimental Botany, Vol. 54, No. 381, pp. 259-270,
January 2, 2003
© 2003 Oxford University Press
Biochemical and physiological studies of Arabidopsis thaliana transgenic lines with repressed expression of the mitochondrial pyruvate dehydrogenase kinase1
Received 22 April 2002; Accepted 30 August 2002
2 National Research Council of Canada, Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, Saskatchewan S7N 0W9, Canada
3 The University of Guelph, Department of Plant Agriculture, Guelph, Ontario N1G 2W1, Canada
1 GenBank/EMBL Accession Number: AJ007312.
4 To whom correspondence should be addressed. Fax: +1 306 975 4839. E-mail: david.taylor{at}nrc.ca
Abbreviations: DAG, diacylglycerol; FFA, free fatty acid; GC, gas chromatography; PA, phosphatidic acid; PC, phosphatidylcholine; PL, polar lipid; SE, standard error; TLE, total lipid extract; TLC, thin layer chromatography; TAG, triacylglycerol.
Pyruvate dehydrogenase kinase (PDHK), a negative regulator of the mitochondrial pyruvate dehydrogenase complex (mtPDC), plays a pivotal role in controlling mtPDC activity, and hence, the TCA cycle and cell respiration. Previously, the cloning of a PDHK cDNA from Arabidopsis thaliana and the effects of constitutively down-regulating its expression on plant growth and development has been reported. The first detailed analyses of the biochemical and physiological effects of partial silencing of the mtPDHK in A. thaliana using antisense constructs driven by both constitutive and seed-specific promoters are reported here. The studies revealed an increased level of respiration in leaves of the constitutive antisense PDHK transgenics; an increase in respiration was also found in developing seeds of the seed-specific antisense transgenics. Both constitutive and seed-specific partial silencing of the mtPDHK resulted in increased seed oil content and seed weight at maturity. Feeding 3-14C pyruvate to bolted stems containing siliques (constitutive transgenics), or to isolated siliques or immature seeds (seed-specific transgenics) confirmed a higher rate of incorporation of radiolabel into all seed lipid species, particularly triacylglycerols. Neither constitutive nor seed-specific partial silencing of PDHK negatively affected overall silique and seed development. Instead, oil and seed yield, and overall plant productivity were improved. These findings suggest that a partial reduction of the repression of the mtPDC by antisense PDHK expression can alter carbon flux and, in particular, the contribution of carbon moieties from pyruvate to fatty acid biosynthesis and storage lipid accumulation in developing seeds, implicating a role for mtPDC in fatty acid biosynthesis in seeds.
Key words: Arabidopsis thaliana, early flowering, mitochondrial pyruvate dehydrogenase complex, plant development, pyruvate dehydrogenase kinase (EC 2.7.1.99), respiration, seed oil content, seed weight.
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