Reduced Arogenate Dehydratase Expression: Ramifications for Photosynthesis and Metabolism
Arogenate dehydratase (ADT) catalyzes the final step of phenylalanine biosynthesis. Previously, lignin contents of ADT deficient Arabidopsis thaliana mutant plants were measured, with these showing significant reductions that increased with the number of isoforms knocked-out. Here we describe the effects of ADT modulation on photosynthetic parameters and overall secondary metabolism in short day length grown plants. To do this, we employed our phenomics facility to determine significant effects on photosynthetic parameters. The data indicated that reduction of carbon flux into phenylalanine biosynthesis in ADT mutants impairs consumption of photosynthetically produced ATP leading to increased ATP/ADP ratio and over-accumulation of transitory starch and lower electron transport rates. The latter is caused by an increased proton motive force across the thylakoid membrane that activates down-regulation of photosystem II activity by the high energy quenching mechanism. At the same time, we have used UPLC-MS based metabolomics analyses to determine changes in secondary metabolite contents. Using this approach, the systemic effects of ADT modulation became apparent, establishing a reduction in flavonoid, phenylpropanoid, lignan and glucosinolate contents; this included glucosinolates that were not aromatic amino acid derived. On the other hand, we observed a significant increase in putatively annotated galactolipids and apocarotenoids. Additionally, we used real-time atmospheric monitoring mass spectrometry to measure differential respiration and carbon fixation rates between wild-type plants and our most extreme ADT knock-out mutant, adt3/4/5/6. We observed that respiration rates were not significantly, different but carbon fixation rates in the adt3/4/5/6 mutant were higher than in wild-type.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1503546
- Report Number(s):
- PNNL-SA-131412
- Journal Information:
- Plant Physiology (Bethesda), Vol. 177, Issue 1; ISSN 0032-0889
- Publisher:
- American Society of Plant Biologists
- Country of Publication:
- United States
- Language:
- English
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