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Identification and characterization of the maize arogenate dehydrogenase gene family.

Holding DR, Meeley RB, Hazebroek J, Selinger D, Gruis F, Jung R, Larkins BA - J. Exp. Bot. (2010)

Bottom Line: In plants, the amino acids tyrosine and phenylalanine are synthesized from arogenate by arogenate dehydrogenase and arogenate dehydratase, respectively, with the relative flux to each being tightly controlled.A Mutator insertion at an equivalent position in AroDH-3, the most closely related family member to AroDH-1, is also associated with opaque endosperm and stunted vegetative growth phenotypes.Overlapping but differential expression patterns as well as subtle mutant effects on the accumulation of tyrosine and phenylalanine in endosperm, embryo, and leaf tissues suggest that the functional redundancy of this gene family provides metabolic plasticity for the synthesis of these important amino acids. mto140/arodh-1 seeds shows a general reduction in zein storage protein accumulation and an elevated lysine phenotype typical of other opaque endosperm mutants, but it is distinct because it does not result from quantitative or qualitative defects in the accumulation of specific zeins but rather from a disruption in amino acid biosynthesis.

View Article: PubMed Central - PubMed

Affiliation: Center for Plant Science Innovation, University of Nebraska, 1901 Vine St., Lincoln, NE 68588, USA. dholding2@unl.edu

ABSTRACT
In plants, the amino acids tyrosine and phenylalanine are synthesized from arogenate by arogenate dehydrogenase and arogenate dehydratase, respectively, with the relative flux to each being tightly controlled. Here the characterization of a maize opaque endosperm mutant (mto140), which also shows retarded vegetative growth, is described The opaque phenotype co-segregates with a Mutator transposon insertion in an arogenate dehydrogenase gene (zmAroDH-1) and this led to the characterization of the four-member family of maize arogenate dehydrogenase genes (zmAroDH-1-zmAroDH-4) which share highly similar sequences. A Mutator insertion at an equivalent position in AroDH-3, the most closely related family member to AroDH-1, is also associated with opaque endosperm and stunted vegetative growth phenotypes. Overlapping but differential expression patterns as well as subtle mutant effects on the accumulation of tyrosine and phenylalanine in endosperm, embryo, and leaf tissues suggest that the functional redundancy of this gene family provides metabolic plasticity for the synthesis of these important amino acids. mto140/arodh-1 seeds shows a general reduction in zein storage protein accumulation and an elevated lysine phenotype typical of other opaque endosperm mutants, but it is distinct because it does not result from quantitative or qualitative defects in the accumulation of specific zeins but rather from a disruption in amino acid biosynthesis.

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Aromatic amino acid pathway in plants.
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fig1: Aromatic amino acid pathway in plants.

Mentions: The characterization of additional starchy endosperm mutants can further our understanding of the mechanisms that lead to the formation of vitreous endosperm, and shed light on general processes of seed metabolism. Here a novel opaque mutant which co-segregates with a Mutator insertion in an arogenate dehydrogenase gene is described. This gene functions in the final steps of the aromatic amino acid pathway that produces tyrosine (Fig. 1). The arogenate route to tyrosine and phenylalanine is one of two distinct pathways that exist in plants, yeast, and bacteria (Stenmark et al., 1974). It involves the conversion of arogenate into tyrosine by arogenate dehydrogenase and into phenylalanine by arogenate dehydratase. The other route involves the transformation of prephenate into p-hydroxyphenyl pyruvate or phenylpyruvate, which are then transaminated into tyrosine or phenylalanine, respectively. Bacteria and yeast use various combinations of the above pathways, often resulting in complex feedback regulation (Legrand et al., 2006). Most plants exclusively use the arogenate pathway to synthesize tyrosine and phenylalanine, which are essential for protein synthesis and many phenylpropanoid compounds. The partitioning between tyrosine and phenylalanine is controlled by the sensitivity of arogenate dehydrogenase to feedback inhibition by tyrosine (Rippert and Matringe, 2002a, b). Control of the end-product is critical given that phenylalanine is the primary substrate for lignin biosynthesis. In this study, the identification and characterization of mutants in AroDH-1 and AroDH-3 genes which exhibit non-lethal opaque endosperm phenotypes are described, and this is discussed in the context of the redundantly expressed arogenate dehydrogenase gene family.


Identification and characterization of the maize arogenate dehydrogenase gene family.

Holding DR, Meeley RB, Hazebroek J, Selinger D, Gruis F, Jung R, Larkins BA - J. Exp. Bot. (2010)

Aromatic amino acid pathway in plants.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2921203&req=5

fig1: Aromatic amino acid pathway in plants.
Mentions: The characterization of additional starchy endosperm mutants can further our understanding of the mechanisms that lead to the formation of vitreous endosperm, and shed light on general processes of seed metabolism. Here a novel opaque mutant which co-segregates with a Mutator insertion in an arogenate dehydrogenase gene is described. This gene functions in the final steps of the aromatic amino acid pathway that produces tyrosine (Fig. 1). The arogenate route to tyrosine and phenylalanine is one of two distinct pathways that exist in plants, yeast, and bacteria (Stenmark et al., 1974). It involves the conversion of arogenate into tyrosine by arogenate dehydrogenase and into phenylalanine by arogenate dehydratase. The other route involves the transformation of prephenate into p-hydroxyphenyl pyruvate or phenylpyruvate, which are then transaminated into tyrosine or phenylalanine, respectively. Bacteria and yeast use various combinations of the above pathways, often resulting in complex feedback regulation (Legrand et al., 2006). Most plants exclusively use the arogenate pathway to synthesize tyrosine and phenylalanine, which are essential for protein synthesis and many phenylpropanoid compounds. The partitioning between tyrosine and phenylalanine is controlled by the sensitivity of arogenate dehydrogenase to feedback inhibition by tyrosine (Rippert and Matringe, 2002a, b). Control of the end-product is critical given that phenylalanine is the primary substrate for lignin biosynthesis. In this study, the identification and characterization of mutants in AroDH-1 and AroDH-3 genes which exhibit non-lethal opaque endosperm phenotypes are described, and this is discussed in the context of the redundantly expressed arogenate dehydrogenase gene family.

Bottom Line: In plants, the amino acids tyrosine and phenylalanine are synthesized from arogenate by arogenate dehydrogenase and arogenate dehydratase, respectively, with the relative flux to each being tightly controlled.A Mutator insertion at an equivalent position in AroDH-3, the most closely related family member to AroDH-1, is also associated with opaque endosperm and stunted vegetative growth phenotypes.Overlapping but differential expression patterns as well as subtle mutant effects on the accumulation of tyrosine and phenylalanine in endosperm, embryo, and leaf tissues suggest that the functional redundancy of this gene family provides metabolic plasticity for the synthesis of these important amino acids. mto140/arodh-1 seeds shows a general reduction in zein storage protein accumulation and an elevated lysine phenotype typical of other opaque endosperm mutants, but it is distinct because it does not result from quantitative or qualitative defects in the accumulation of specific zeins but rather from a disruption in amino acid biosynthesis.

View Article: PubMed Central - PubMed

Affiliation: Center for Plant Science Innovation, University of Nebraska, 1901 Vine St., Lincoln, NE 68588, USA. dholding2@unl.edu

ABSTRACT
In plants, the amino acids tyrosine and phenylalanine are synthesized from arogenate by arogenate dehydrogenase and arogenate dehydratase, respectively, with the relative flux to each being tightly controlled. Here the characterization of a maize opaque endosperm mutant (mto140), which also shows retarded vegetative growth, is described The opaque phenotype co-segregates with a Mutator transposon insertion in an arogenate dehydrogenase gene (zmAroDH-1) and this led to the characterization of the four-member family of maize arogenate dehydrogenase genes (zmAroDH-1-zmAroDH-4) which share highly similar sequences. A Mutator insertion at an equivalent position in AroDH-3, the most closely related family member to AroDH-1, is also associated with opaque endosperm and stunted vegetative growth phenotypes. Overlapping but differential expression patterns as well as subtle mutant effects on the accumulation of tyrosine and phenylalanine in endosperm, embryo, and leaf tissues suggest that the functional redundancy of this gene family provides metabolic plasticity for the synthesis of these important amino acids. mto140/arodh-1 seeds shows a general reduction in zein storage protein accumulation and an elevated lysine phenotype typical of other opaque endosperm mutants, but it is distinct because it does not result from quantitative or qualitative defects in the accumulation of specific zeins but rather from a disruption in amino acid biosynthesis.

Show MeSH