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Published on July 11, 2008; 10.1104/pp.108.124057

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Received June 5, 2008
Accepted July 7, 2008

The Coenzyme A biosynthetic enzyme phosphopantetheine adenylyltransferase plays a crucial role for plant growth, salt/osmotic-stress resistance and seed lipid storage

Silvia Rubio , Lynne Whitehead , Tony R. Larson , Ian A. Graham , and Pedro L. Rodriguez *

Instituto de Biologia Molecular y Celular de Plantas, Universidad Politecnica de Valencia-Consejo Superior de Investigaciones Cientificas, ES-46022 Valencia, Spain; CNAP, Department of Biology, University of York, PO Box 373, York YO10 5YW, UK

* Corresponding author; email: prodriguez{at}ibmcp.upv.es.

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 work, we have characterized a viable 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 a ~90 % reduction in PPAT transcript levels and was severely impaired in plant growth and seed production. The sum of CoA and AcCoA 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 over-expressing (OE) lines showed on average ~1.6-fold higher levels of CoA + AcCoA levels, as well as enhanced vegetative and reproductive growth and salt/osmotic stress resistance. Interestingly, dry seeds of OE lines contained between 35-50% more FAs 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.






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