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

Abstract

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.

Diacylglycerol Acyltransferase 1 Is Regulated by Its N-Terminal Domain in Response to Allosteric Effectors

“…Previously, CoA was found to be a feedback inhibitor of phosphopantetheine adenylyltransferase, which is a regulatory enzyme catalyzing the second last reaction involved in CoA biosynthesis (Rubio et al, 2008). The IC 50 of CoA for phosphopantetheine adenylyltransferase is about 39 mM, which is close to the IC 50 of about 47 mM for the CoA-BnaDGAT1 interaction based on our kinetic analysis.…”

Duplicate Maize Wrinkled1 Transcription Factors Activate Target Genes Involved in Seed Oil Biosynthesis

“…However, it is known that CoA is present in all compartments and that precursors are shuttled between compartments (Rubio et al, 2008). In addition, the overexpression of a CoA biosynthetic enzyme has been shown to lead to increased seed oil content in Arabidopsis (Rubio et al, 2008). The maize acetyl-CoA acetyltransferase shows similarity to ACAT1 and ACAT2 from Arabidopsis, suggesting a function in the mevalonate pathway leading to isoprenoid biosynthesis rather than in the degradation of Lys or Ile (Carrie et al, 2007).…”

“…At first sight, their predicted localization in mitochondria (ketopantoate hydroxymethyltransferase, carbonic anhydrase) or the cytoplasm (acetyl-CoA acetyltransferase) makes it difficult to establish a direct link to fatty acid biosynthesis localized in plastids. However, it is known that CoA is present in all compartments and that precursors are shuttled between compartments (Rubio et al, 2008). In addition, the overexpression of a CoA biosynthetic enzyme has been shown to lead to increased seed oil content in Arabidopsis (Rubio et al, 2008).…”

Development of transgenic plants in jatropha with drought tolerance

“…Phosphopanthetheine adenylyltransferase (PPAT) catalyzes the penultimate step in the CoA biosynthetic pathway (Kupke et al 2003). Recently, the action of the PPAT gene of Arabidopsis (AtPPAT) was analyzed (Rubio et al 2008). e knockdown mutant of the gene exhibited severely impaired growth and seed production.…”

“…e last overexpresses the Synechococcus GSMT and DMT genes encoding glycine sarcosine methyltransferase and sarcosine dimethylglycine methyltransferase, respectively, both of which catalyze glycine betaine production. Transgenic Arabidopsis plants that overexpress either of these gene sets exhibit improved drought tolerance (Rubio et al 2008;Nelson et al 2007;Waditee et al 2005). PPAT improves drought tolerance by enhancing metabolic activitiy; NF-YB enhances the response to the drought stress by affecting the expressions of downstream genes; and glycine betaine diminishes drought stress as an osmolyte.…”