Two <i>Arabidopsis</i> Threonine Aldolases Are Nonredundant and Compete with Threonine Deaminase for a Common Substrate Pool

Joshi, Vijay; Laubengayer, Karen M.; Schauer, Nicolas; Fernie, Alisdair R.; Jander, Georg

doi:10.1105/tpc.106.044958

Cited by 86 publications

(77 citation statements)

References 52 publications

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“…First, a growing body of evidence points to major roles of amino acid catabolism and interconversion in regulating levels of six of the nine free essential amino acids (Ile, Leu, Lys, Met, Thr, and Val) in seeds of a variety of plants (Karchi et al, 1994;Zhu and Galili, 2003;Jander et al, 2004;Joshi et al, 2006;Lee et al, 2008;Gu et al, 2010;Lu et al, 2011;Angelovici et al, 2013). These results indicate that modifying catabolism has the potential to improve the nutritional quality of crop seeds and vegetative tissues.…”

Section: Broader Implicationsmentioning

confidence: 93%

The Impact of the Branched-Chain Ketoacid Dehydrogenase Complex on Amino Acid Homeostasis in Arabidopsis

Peng¹,

Uygun²

2015

Plant Physiol.

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The branched-chain amino acids (BCAAs) Leu, Ile, and Val are among nine essential amino acids that must be obtained from the diet of humans and other animals, and can be nutritionally limiting in plant foods. Despite genetic evidence of its importance in regulating seed amino acid levels, the full BCAA catabolic network is not completely understood in plants, and limited information is available regarding its regulation. In this study, transcript coexpression analyses revealed positive correlations among BCAA catabolism genes in stress, development, diurnal/circadian, and light data sets. A core subset of BCAA catabolism genes, including those encoding putative branched-chain ketoacid dehydrogenase subunits, is highly expressed during the night in plants on a diel cycle and in prolonged darkness. Mutants defective in these subunits accumulate higher levels of BCAAs in mature seeds, providing genetic evidence for their function in BCAA catabolism. In addition, prolonged dark treatment caused the mutants to undergo senescence early and overaccumulate leaf BCAAs. These results extend the previous evidence that BCAAs can be catabolized and serve as respiratory substrates at multiple steps. Moreover, comparison of amino acid profiles between mature seeds and darktreated leaves revealed differences in amino acid accumulation when BCAA catabolism is perturbed. Together, these results demonstrate the consequences of blocking BCAA catabolism during both normal growth conditions and under energy-limited conditions.The branched-chain amino acids (BCAAs) Leu, Ile, and Val are among nine amino acids essential for humans and other animals because they cannot be synthesized de novo (Harper et al., 1984). Plants synthesize BCAAs and are the main source of these essential nutrients in the diets of humans and agriculturally important animals. In addition to their nutritional value, BCAAs and BCAA-derived metabolites such as glucosinolates, fatty acids, and acyl sugars contribute to plant growth, development, defense, and flavor (Mikkelsen and Halkier, 2003;Taylor et al., 2004;Ishizaki et al., 2005;Slocombe et al., 2008;Araújo et al., 2010;Ding et al., 2012;Kochevenko et al., 2012).The BCAA biosynthetic pathway and its regulation have been investigated in Arabidopsis (Arabidopsis thaliana) and other plants for the past two decades, in large part because of the commercial importance of herbicides that inhibit acetohydroxy acid synthase, which is the committing enzyme of BCAA biosynthesis (Singh and Shaner, 1995;Aubert et al., 1997;Singh, 1999;McCourt et al., 2006;Tan et al., 2006;Binder, 2010;Chen et al., 2010;Yu et al., 2010). Strong correlations between the levels of free BCAAs were found in wildtype Arabidopsis seeds and tomato (Solanum lycopersicum) fruits Lu et al., 2008), which suggests coregulation of biosynthesis and/or degradation. This presumably is due, at least in part, to the fact that they share four common biosynthetic enzymes and three catabolic steps. However, despite long-term interest in the desirability of optim...

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Section: Broader Implicationsmentioning

confidence: 93%

The Impact of the Branched-Chain Ketoacid Dehydrogenase Complex on Amino Acid Homeostasis in Arabidopsis

Peng¹,

Uygun²

2015

Plant Physiol.

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“…In vitro enzyme assays, as well as complementation of an S. cerevisiae gly1 shm1 shm2 mutant, which is a glycine auxotroph (McNeil et al, 1994;Monschau et al, 1997), showed that two A. thaliana genes, At1g08630 (THA1) and At3g04520 (THA2) encode threonine aldolases (Jander et al, 2004;Joshi et al, 2006). Whereas tha1 mutations greatly increase seed threonine content (Jander et al, 2004), tha2 mutations cause a lethal albino phenotype (Joshi et al, 2006). Rescue of a tha1 tha2 double mutant by overexpression of threonine deaminase (At3g10050) shows that glycine formation from threonine is not essential for A. thaliana, and that the lethal effects of tha2 mutations may result from the accumulation of excess threonine.…”

Section: Threonine Catabolismmentioning

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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“…For amino acid analysis, samples were analyzed using a Waters 2790 HPLC system as described previously (Joshi et al, 2006), with a minor modification whereby the ratio of tissue to extraction buffer was 1:3. For measuring leaf DIMBOA-Glc content, sample extraction and HPLC analysis were performed as described previously (Mijares et al, 2013).…”

Section: Targeted and Untargeted Metabolite Assaysmentioning

confidence: 99%

Dynamic maize responses to aphid feeding are revealed by a time series of transcriptomic and metabolomic assays

et al. 2015

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(A.H.); 0000-0002-9675-934X (G.J.).As a response to insect attack, maize (Zea mays) has inducible defenses that involve large changes in gene expression and metabolism. Piercing/sucking insects such as corn leaf aphid (Rhopalosiphum maidis) cause direct damage by acquiring phloem nutrients as well as indirect damage through the transmission of plant viruses. To elucidate the metabolic processes and gene expression changes involved in maize responses to aphid attack, leaves of inbred line B73 were infested with corn leaf aphids for 2 to 96 h. Analysis of infested maize leaves showed two distinct response phases, with the most significant transcriptional and metabolic changes occurring in the first few hours after the initiation of aphid feeding. After 4 d, both gene expression and metabolite profiles of aphid-infested maize reverted to being more similar to those of control plants. Although there was a predominant effect of salicylic acid regulation, gene expression changes also indicated prolonged induction of oxylipins, although not necessarily jasmonic acid, in aphid-infested maize. The role of specific metabolic pathways was confirmed using Dissociator transposon insertions in maize inbred line W22. Mutations in three benzoxazinoid biosynthesis genes, Bx1, Bx2, and Bx6, increased aphid reproduction. In contrast, progeny production was greatly decreased by a transposon insertion in the single W22 homolog of the previously uncharacterized B73 terpene synthases TPS2 and TPS3. Together, these results show that maize leaves shift to implementation of physical and chemical defenses within hours after the initiation of aphid feeding and that the production of specific metabolites can have major effects in maize-aphid interactions.

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Two Arabidopsis Threonine Aldolases Are Nonredundant and Compete with Threonine Deaminase for a Common Substrate Pool

Cited by 86 publications

References 52 publications

The Impact of the Branched-Chain Ketoacid Dehydrogenase Complex on Amino Acid Homeostasis in Arabidopsis

The Impact of the Branched-Chain Ketoacid Dehydrogenase Complex on Amino Acid Homeostasis in Arabidopsis

Aspartate-Derived Amino Acid Biosynthesis inArabidopsis thaliana

Dynamic maize responses to aphid feeding are revealed by a time series of transcriptomic and metabolomic assays

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