Branched‐chain amino acid metabolism in higher plants

Binder, Stefan; Knill, Tanja; Schuster, Joachim

doi:10.1111/j.1399-3054.2006.00800.x

Cited by 132 publications

(120 citation statements)

References 58 publications

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“…Furthermore, the branched chain amino acids Ile and Val, which derive from pyruvate (Binder et al, 2007), were significantly higher after 27 d of growth in the old5 mutant. Ile and Val have previously been documented to accumulate in mutants of the electron-transfer flavoprotein complex, which display accelerated dark-induced senescence (Ishizaki et al, , 2006.…”

Section: Old5 Is Characterized By Increased Tricarboxylic Acid Cycle mentioning

confidence: 99%

TheArabidopsis onset of leaf death5Mutation of Quinolinate Synthase Affects Nicotinamide Adenine Dinucleotide Biosynthesis and Causes Early Ageing

et al. 2008

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Leaf senescence in Arabidopsis thaliana is a strict, genetically controlled nutrient recovery program, which typically progresses in an age-dependent manner. Leaves of the Arabidopsis onset of leaf death5 (old5) mutant exhibit early developmental senescence. Here, we show that OLD5 encodes quinolinate synthase (QS), a key enzyme in the de novo synthesis of NAD. The Arabidopsis QS was previously shown to carry a Cys desulfurase domain that stimulates reconstitution of the oxygen-sensitive Fe-S cluster that is required for QS activity. The old5 lesion in this enzyme does not affect QS activity but it decreases its Cys desulfurase activity and thereby the long-term catalytic competence of the enzyme. The old5 mutation causes increased NAD steady state levels that coincide with increased activity of enzymes in the NAD salvage pathway. NAD plays a key role in cellular redox reactions, including those of the tricarboxylic acid cycle. Broad-range metabolite profiling of the old5 mutant revealed that it contains higher levels of tricarboxylic acid cycle intermediates and nitrogen-containing amino acids. The mutant displays a higher respiration rate concomitant with increased expression of oxidative stress markers. We postulate that the alteration in the oxidative state is integrated into the plant developmental program, causing early ageing of the mutant.

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Section: Old5 Is Characterized By Increased Tricarboxylic Acid Cycle mentioning

confidence: 99%

TheArabidopsis onset of leaf death5Mutation of Quinolinate Synthase Affects Nicotinamide Adenine Dinucleotide Biosynthesis and Causes Early Ageing

et al. 2008

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“…The next two enzymes in the isoleucine biosynthetic pathway, ketol-acid reductoisomerase (EC 1.1.1.86; At3g58610) and dihydroxy-acid dehydratase (EC 4.2.1.9; At3g23940) remain uncharacterized in A. thaliana (Binder et al, 2007). So far, genes encoding these enzymes have been identified and named based primarily on the similarity to those encoding ketol-acid reductoisomerase and dihydroxy-acid dehydratase in other species.…”

Section: Isoleucine Biosynthesismentioning

confidence: 99%

Aspartate-Derived Amino Acid Biosynthesis inArabidopsis thaliana

Jander

Joshi

2009

The Arabidopsis Book

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The aspartate-derived amino acid pathway in plants leads to the biosynthesis of lysine, methionine, threonine, and isoleucine. These four amino acids are essential in the diets of humans and other animals, but are present in growthlimiting quantities in some of the world's major food crops. Genetic and biochemical approaches have been used for the functional analysis of almost all Arabidopsis thaliana enzymes involved in aspartate-derived amino acid biosynthesis. The branch-point enzymes aspartate kinase, dihydrodipicolinate synthase, homoserine dehydrogenase, cystathionine gamma synthase, threonine synthase, and threonine deaminase contain well-studied sites for allosteric regulation by pathway products and other plant metabolites. In contrast, relatively little is known about the transcriptional regulation of amino acid biosynthesis and the mechanisms that are used to balance aspartatederived amino acid biosynthesis with other plant metabolic needs. The aspartate-derived amino acid pathway provides excellent examples of basic research conducted with A. thaliana that has been used to improve the nutritional quality of crop plants, in particular to increase the accumulation of lysine in maize and methionine in potatoes.

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“…Plant AHAS is inhibited by all three BCAAs, with valine and leucine being particularly potent (Miflin and Cave, 1972). In addition to AHAS, threonine dehydratase and isopropylmalate synthase are also inhibited by their end products, isoleucine and leucine, respectively (Singh and Shaner, 1995;Binder et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Genetic analysis of pathway regulation for enhancing branched‐chain amino acid biosynthesis in plants

et al. 2010

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SUMMARYThe branched-chain amino acids (BCAAs) valine, leucine and isoleucine are essential amino acids that play critical roles in animal growth and development. Animals cannot synthesize these amino acids and must obtain them from their diet. Plants are the ultimate source of these essential nutrients, and they synthesize BCAAs through a conserved pathway that is inhibited by its end products. This feedback inhibition has prevented scientists from engineering plants that accumulate high levels of BCAAs by simply over-expressing the respective biosynthetic genes. To identify components critical for this feedback regulation, we performed a genetic screen for Arabidopsis mutants that exhibit enhanced resistance to BCAAs. Multiple dominant allelic mutations in the VALINE-TOLERANT 1 (VAT1) gene were identified that conferred plant resistance to valine inhibition. Map-based cloning revealed that VAT1 encodes a regulatory subunit of acetohydroxy acid synthase (AHAS), the first committed enzyme in the BCAA biosynthesis pathway. The VAT1 gene is highly expressed in young, rapidly growing tissues. When reconstituted with the catalytic subunit in vitro, the vat1 mutantcontaining AHAS holoenzyme exhibits increased resistance to valine. Importantly, transgenic plants expressing the mutated vat1 gene exhibit valine tolerance and accumulate higher levels of BCAAs. Our studies not only uncovered regulatory characteristics of plant AHAS, but also identified a method to enhance BCAA accumulation in crop plants that will significantly enhance the nutritional value of food and feed.

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Branched‐chain amino acid metabolism in higher plants

Cited by 132 publications

References 58 publications

TheArabidopsis onset of leaf death5Mutation of Quinolinate Synthase Affects Nicotinamide Adenine Dinucleotide Biosynthesis and Causes Early Ageing

TheArabidopsis onset of leaf death5Mutation of Quinolinate Synthase Affects Nicotinamide Adenine Dinucleotide Biosynthesis and Causes Early Ageing

Aspartate-Derived Amino Acid Biosynthesis inArabidopsis thaliana

Genetic analysis of pathway regulation for enhancing branched‐chain amino acid biosynthesis in plants

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