Reduced activity of <i>Arabidopsis thaliana</i> HMT2, a methionine biosynthetic enzyme, increases seed methionine content

Lee, Minsang; Huang, Tengfang; Toro‐Ramos, Tatiana; Fraga, Michele; Last, Robert L.; Jander, Georg

doi:10.1111/j.1365-313x.2008.03419.x

Cited by 56 publications

(59 citation statements)

References 29 publications

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“…These results indicate that modifying catabolism has the potential to improve the nutritional quality of crop seeds and vegetative tissues. However, a variety of pleiotropic effects were seen for these examples, ranging from increased seed Cys in threonine aldolase1 mutants (Lu et al, 2008) to broader amino acid increases in Lys overproducing lines (Karchi et al, 1994;Zhu and Galili, 2003) and BCAA catabolic mutants (Gu et al, 2010;Lu et al, 2011;and this study), and defects in vegetative and seed development or seed viability (Zhu and Galili, 2004;Lee et al, 2008;Ding et al, 2012). It is not surprising that these relatively old processes are broadly connected and difficult to perturb without resultant undesirable effects (Milo and Last, 2012).…”

Section: Broader Implicationsmentioning

confidence: 66%

“…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: 99%

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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: 66%

Section: Broader Implicationsmentioning

confidence: 99%

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

Peng¹,

Uygun²

2015

Plant Physiol.

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“…However, despite the efficient transport capability of SMM, Arabidopsis and maize mmt mutants, which are unable to synthesize SMM, grow and reproduce normally, suggesting a minimal regulatory role for SMM in sulfur transport of at least these two species (Kocsis et al, 2003). Notwithstanding, a recent report (Lee et al, 2008) showed that a mutant Arabidopsis plant overaccumulating Met in its seeds is due to a mutation eliminating the activity of HMT2, one of the three Arabidopsis HMT isozymes that recycle SMM into Met (Lee et al, 2008). The HMT2 gene is expressed in vegetative tissues where it apparently shifts the balance from Met to SMM in these source tissues.…”

Section: Improving Met Content By Genetic Engineeringmentioning

confidence: 98%

Improving the Content of Essential Amino Acids in Crop Plants: Goals and Opportunities

2008

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“…The enzymes homocysteine methyltransferase and methionine methyltransferase catalyze the interconversion of methionine and S-methylmethionine (Figure 8), a metabolic cycle that functions in phloem loading and amino transport (Bourgis et al, 1999;Lee et al, 2008). Whereas homocysteine methyltransferase forms two molecules of methionine from S-methylmethionine and homocysteine, methionine methyltransferase uses S-adenosylmethionine as a methyl group donor to form S-methylmethionine from methionine.…”

Section: The S-methylmethionine Cyclementioning

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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Reduced activity of Arabidopsis thaliana HMT2, a methionine biosynthetic enzyme, increases seed methionine content

Cited by 56 publications

References 29 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

Improving the Content of Essential Amino Acids in Crop Plants: Goals and Opportunities

Aspartate-Derived Amino Acid Biosynthesis inArabidopsis thaliana

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