OPEN ACCESS ARTICLE

This Article Free via Open Access: OA OA Full Text Full Text (PDF) Supplemental Data OA All Versions of this Article: 148/2/1055    most recent pp.108.125237v1 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 (2) Citing Articles via Google Scholar Google Scholar Articles by Haas, F. H. Articles by Hell, R. Search for Related Content PubMed PubMed Citation Articles by Haas, F. H. Articles by Hell, R. Agricola Articles by Haas, F. H. Articles by Hell, R.

BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Mitochondrial Serine Acetyltransferase Functions as a Pacemaker of Cysteine Synthesis in Plant Cells^{1,[C],[W],[OA]}

Heidelberg Institute for Plant Sciences, Heidelberg University, 69120 Heidelberg, Germany (F.H.H., C.H., M.W., R.H.); and German Cancer Research Center, 69120 Heidelberg, Germany (R.Q., A.B.)

Cysteine (Cys) synthesis in plants is carried out by two sequential reactions catalyzed by the rate-limiting enzyme serine acetyltransferase (SAT) and excess amounts of O-acetylserine(thiol)lyase. Why these reactions occur in plastids, mitochondria, and cytosol of plants remained unclear. Expression of artificial microRNA (amiRNA) against Sat3 encoding mitochondrial SAT3 in transgenic Arabidopsis (Arabidopsis thaliana) plants demonstrates that mitochondria are the most important compartment for the synthesis of O-acetylserine (OAS), the precursor of Cys. Reduction of RNA levels, protein contents, SAT enzymatic activity, and phenotype strongly correlate in independent amiSAT3 lines and cause significantly retarded growth. The expression of the other four Sat genes in the Arabidopsis genome are not affected by amiRNA-SAT3 according to quantitative real-time polymerase chain reaction and microarray analyses. Application of radiolabeled serine to leaf pieces revealed severely reduced incorporation rates into Cys and even more so into glutathione. Accordingly, steady-state levels of OAS are 4-fold reduced. Decrease of sulfate reduction-related genes is accompanied by an accumulation of sulfate in amiSAT3 lines. These results unequivocally show that mitochondria provide the bulk of OAS in the plant cell and are the likely site of flux regulation. Together with recent data, the cytosol appears to be a major site of Cys synthesis, while plastids contribute reduced sulfur as sulfide. Thus, Cys synthesis in plants is significantly different from that in nonphotosynthetic eukaryotes at the cellular level.

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: Rüdiger Hell (rhell{at}hip.uni-heidelberg.de).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.125237

^* Corresponding author; e-mail rhell{at}hip.uni-heidelberg.de.

Received June 24, 2008; accepted August 25, 2008; published August 27, 2008.

This article has been cited by other articles:

				L. Tabe, M. Wirtz, L. Molvig, M. Droux, and R. Hell Overexpression of serine acetlytransferase produced large increases in O-acetylserine and free cysteine in developing seeds of a grain legume J. Exp. Bot., November 25, 2009; (2009) erp338v1. [Abstract] [Full Text] [PDF]

				G. Queval, D. Thominet, H. Vanacker, M. Miginiac-Maslow, B. Gakiere, and G. Noctor H2O2-Activated Up-Regulation of Glutathione in Arabidopsis Involves Induction of Genes Encoding Enzymes Involved in Cysteine Synthesis in the Chloroplast Mol Plant, March 1, 2009; 2(2): 344 - 356. [Abstract] [Full Text] [PDF]