This Article Full Text Full Text (PDF) All Versions of this Article: 141/3/879    most recent pp.106.081174v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (9) Citing Articles via Google Scholar Google Scholar Articles by Weise, S. E. Articles by Sharkey, T. D. Search for Related Content PubMed PubMed Citation Articles by Weise, S. E. Articles by Sharkey, T. D. Agricola Articles by Weise, S. E. Articles by Sharkey, T. D.

BIOENERGETICS AND PHOTOSYNTHESIS

Carbon Balance and Circadian Regulation of Hydrolytic and Phosphorolytic Breakdown of Transitory Starch¹

Department of Botany, University of Wisconsin, Madison, Wisconsin 53726

Transitory starch is formed in chloroplasts during the day and broken down at night. Transitory starch degradation could be regulated by light, circadian rhythms, or carbon balance. To test the role of these potential regulators, starch breakdown rates and metabolites were measured in bean (Phaseolus vulgaris) and Arabidopsis (Arabidopsis thaliana) plants. In continuous light, starch and maltose levels oscillated in a circadian manner. Under photorespiratory conditions, transitory starch breakdown occurred in the light faster than at night and glucose-6-P (G6P) was elevated. Nonaqueous fractionation showed that the increase in G6P occurred in the chloroplast. When Arabidopsis plants lacking the plastidic starch phosphorylase enzyme were placed under photorespiratory conditions, G6P levels remained constant, indicating that the increased chloroplastic G6P resulted from phosphorolytic starch degradation. Maltose was increased under photorespiratory conditions in both wild type and plants lacking starch phosphorylase, indicating that regulation of starch breakdown may occur at a point preceding the division of the hydrolytic and phosphorolytic pathways. When bean leaves were held in N₂ to suppress photosynthesis and Suc synthesis without increasing photorespiration, starch breakdown did not occur and maltose and G6P levels remained constant. The redox status of the chloroplasts was found to be oxidized under conditions favoring starch degradation.

² Present address: Department of Metabolic Biology, John Innes Centre, Norwich NR4 7UH, UK.

³ Present address: U.S. Department of Agriculture Photosynthesis Research Unit, University of Illinois, 190 ERML, 1201 W. Gregory, Urbana, IL 61801.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Thomas D. Sharkey (tsharkey{at}wisc.edu).

Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.106.081174.

^* Corresponding author; e-mail tsharkey{at}wisc.edu; fax 608–262–7509.

Received March 29, 2006; returned for revision May 3, 2006; accepted May 7, 2006.

This article has been cited by other articles:

				A. M. Borland, H. Griffiths, J. Hartwell, and J. A. C. Smith Exploiting the potential of plants with crassulacean acid metabolism for bioenergy production on marginal lands J. Exp. Bot., July 1, 2009; 60(10): 2879 - 2896. [Abstract] [Full Text] [PDF]

				D. C. Fulton, M. Stettler, T. Mettler, C. K. Vaughan, J. Li, P. Francisco, M. Gil, H. Reinhold, S. Eicke, G. Messerli, et al. {beta}-AMYLASE4, a Noncatalytic Protein Required for Starch Breakdown, Acts Upstream of Three Active {beta}-Amylases in Arabidopsis Chloroplasts PLANT CELL, April 1, 2008; 20(4): 1040 - 1058. [Abstract] [Full Text] [PDF]

				S. Aluri and M. Buttner Identification and functional expression of the Arabidopsis thaliana vacuolar glucose transporter 1 and its role in seed germination and flowering PNAS, February 13, 2007; 104(7): 2537 - 2542. [Abstract] [Full Text] [PDF]