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BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

The Coenzyme A Biosynthetic Enzyme Phosphopantetheine Adenylyltransferase Plays a Crucial Role in Plant Growth, Salt/Osmotic Stress Resistance, and Seed Lipid Storage^1,[W]

Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia/Consejo Superior de Investigaciones Científicas, ES–46022 Valencia, Spain (S.R., P.L.R.); and Centre for Novel Agricultural Products, Department of Biology, University of York, York YO10 5YW, United Kingdom (L.W., T.R.L., I.A.G.)

Coenzyme A (CoA) is an essential cofactor in the metabolism of both prokaryotic and eukaryotic organisms and a universal five-step pathway is utilized to synthesize CoA from pantothenate. Null mutations in two of the five steps of this pathway led to embryo lethality and therefore viable reduction-of-function mutations are required to further study its role in plant biology. In this article, we have characterized a viable Arabidopsis (Arabidopsis thaliana) T-DNA mutant affected in the penultimate step of the CoA biosynthesis pathway, which is catalyzed by the enzyme phosphopantetheine adenylyltransferase (PPAT). This ppat-1 knockdown mutation showed an approximately 90% reduction in PPAT transcript levels and was severely impaired in plant growth and seed production. The sum of CoA and acetyl-CoA levels was severely reduced (60%–80%) in ppat-1 seedlings compared to wild type, and catabolism of storage lipids during seedling establishment was delayed. Conversely, PPAT overexpressing lines showed, on average, approximately 1.6-fold higher levels of CoA + acetyl-CoA levels, as well as enhanced vegetative and reproductive growth and salt/osmotic stress resistance. Interestingly, dry seeds of overexpressing lines contained between 35% to 50% more fatty acids than wild type, which suggests that CoA biosynthesis plays a crucial role in storage oil accumulation. Finally, biochemical analysis of the recombinant PPAT enzyme revealed an inhibitory effect of CoA on PPAT activity. Taken together, these results suggest that the reaction catalyzed by PPAT is a regulatory step in the CoA biosynthetic pathway that plays a key role for plant growth, stress resistance, and seed lipid storage.

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: Pedro L. Rodriguez (prodriguez{at}ibmcp.upv.es).

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

www.plantphysiol.org/cgi/doi/10.1104/pp.108.124057

^* Corresponding author; e-mail prodriguez{at}ibmcp.upv.es.

Received June 5, 2008; accepted July 7, 2008; published July 11, 2008.