JXB Advance Access published online on February 4, 2008
Journal of Experimental Botany, doi:10.1093/jxb/erm312
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Decreased expression of plastidial adenylate kinase in potato tubers results in an enhanced rate of respiration and a stimulation of starch synthesis that is attributable to post-translational redox-activation of ADP-glucose pyrophosphorylase
1Max-Planck-Institute of Molecular Plant Physiology, Am Muehlenberg 1, D-14476 Potsdam-Golm, Germany
2CINVESTAV-IPN, Campus Guanajuato, 36821 Inapuato, Mexico
* To whom correspondence should be addressed. E-mail: geigenberger{at}mpimp-golm.mpg.de
Adenine nucleotides are of general importance for many aspects of cell function, but their role in the regulation of biosynthetic processes is still unclear. It was previously reported that decreased expression of plastidial adenylate kinase, catalysing the interconversion of ATP and AMP to ADP, leads to increased adenylate pools and starch content in transgenic potato tubers. However, the underlying mechanisms were not elucidated. Here, it is shown that decreased expression of plastidial adenylate kinase in growing tubers leads to increased rates of respiratory oxygen consumption and increased carbon fluxes into starch. Increased rates of starch synthesis were accompanied by post-translational redox-activation of ADP-glucose pyrophosphorylase (AGPase), catalysing the key regulatory step of starch synthesis in the plastid, while there were no substantial changes in metabolic intermediates or sugar levels. A similar increase in post-translational redox-activation of AGPase was found after supplying adenine to wild-type potato tuber discs to increase adenine nucleotide levels. Results provide first evidence for a link between redox-activation of AGPase and adenine nucleotide levels in plants.
Key words: Adenylate kinase, ADPglucose pyrophosphorylase, plastid, redox-regulation, potato, respiration, starch
Received 18 September 2007; Revised 12 November 2007 Accepted 13 November 2007
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