Present address: Metanomics GmbH, Tegeler Weg 33, 10589 Berlin, Germany.
Mutagenesis of cysteine 81 prevents dimerization of the APS1 subunit of ADP-glucose pyrophosphorylase and alters diurnal starch turnover in Arabidopsis thaliana leaves
Article first published online: 28 DEC 2011
© 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd
The Plant Journal
Volume 70, Issue 2, pages 231–242, April 2012
How to Cite
Hädrich, N., Hendriks, J. H.M., Kötting, O., Arrivault, S., Feil, R., Zeeman, S. C., Gibon, Y., Schulze, W. X., Stitt, M. and Lunn, J. E. (2012), Mutagenesis of cysteine 81 prevents dimerization of the APS1 subunit of ADP-glucose pyrophosphorylase and alters diurnal starch turnover in Arabidopsis thaliana leaves. The Plant Journal, 70: 231–242. doi: 10.1111/j.1365-313X.2011.04860.x
- Issue published online: 3 APR 2012
- Article first published online: 28 DEC 2011
- Accepted manuscript online: 18 NOV 2011 11:43PM EST
- Received 16 July 2011; revised 14 November 2011; accepted 17 November 2011; published online 28 December 2011.
- ADP-glucose pyrophosphorylase;
- Arabidopsis thaliana;
- site-directed mutagenesis;
Many plants, including Arabidopsis thaliana, retain a substantial portion of their photosynthate in leaves in the form of starch, which is remobilized to support metabolism and growth at night. ADP-glucose pyrophosphorylase (AGPase) catalyses the first committed step in the pathway of starch synthesis, the production of ADP-glucose. The enzyme is redox-activated in the light and in response to sucrose accumulation, via reversible breakage of an intermolecular cysteine bridge between the two small (APS1) subunits. The biological function of this regulatory mechanism was investigated by complementing an aps1 null mutant (adg1) with a series of constructs containing a full-length APS1 gene encoding either the wild-type APS1 protein or mutated forms in which one of the five cysteine residues was replaced by serine. Substitution of Cys81 by serine prevented APS1 dimerization, whereas mutation of the other cysteines had no effect. Thus, Cys81 is both necessary and sufficient for dimerization of APS1. Compared to control plants, the adg1/APS1C81S lines had higher levels of ADP-glucose and maltose, and either increased rates of starch synthesis or a starch-excess phenotype, depending on the daylength. APS1 protein levels were five- to tenfold lower in adg1/APS1C81S lines than in control plants. These results show that redox modulation of AGPase contributes to the diurnal regulation of starch turnover, with inappropriate regulation of the enzyme having an unexpected impact on starch breakdown, and that Cys81 may play an important role in the regulation of AGPase turnover.