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evolution
plant ADTs and prephenate dehydratases, EC 4.2.1.51, share many common features allowing them to act as dehydratase/decarboxylases, but group independently conferring distinct substrate specificities, sequence comparisons, overview
malfunction
ADT1 suppression leads to downregulation of carbon flux toward shikimic acid, but exogenous supply of shikimate bypasses this negative regulation and results in elevated arogenate accumulation
malfunction
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the rice mtr1 mutant accumulates Phe and Trp. Calli overexpressing mtr1 mutant show elevated levels of Phe, Trp, phenylpropanoids and an indole alkaloid, and is resistant to 5-methyltryptophan treatment. Mtr1 mutants display the same short culm and reduced spikelet number that are observed in transgenic rice accumulating Trp, but Mtr1 mutants show slightly better germination frequency and spikelet fertility
malfunction
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phenotypes of adt isozyme knockout mutants, overview
malfunction
addition of Phe to the medium dramatically increases anthocyanin content in the wild-type plants and rescues the phenotype of the adt1 adt3 double mutant regarding the anthocyanin accumulation. mRNA levels of ADTs ae dramatically increased in transgenic plants. ADT1/3 mutation greatly affects cold-induced anthocyanin accumulation. Single mutants have no obvious defects in plant growth compared with the wild-type, except for isozme ADT2, whereas the adt4/5 double mutant and adt4/5 combined with other mutants including adt1, adt3, adt1/3, adt3/6, and adt1/3/6 display a dwarf phenotype. In all triple mutants, the mutants with adt1/3 produce the lowest levels of anthocyanin, about 40%-55% of wild-type, compared with other triple mutants such as adt1/4/5. Although the quintuple adt1/3/4/5/6 mutant produce the lowest level (about 35% of the wild-type level) of anthocyanin, no significant difference is detected between the quintuple and quadruple mutants (adt1/3/4/5, adt1/3/4/6, and adt1/3/5/6). The anthocyanin profile is not altered in adt mutants, the adt1/3/4/5/6 quintuple mutant still produces about 30% of wild-type anthocyanin content, overview
malfunction
addition of Phe to the medium dramatically increases anthocyanin content in the wild-type plants and rescues the phenotype of the adt1 adt3 double mutant regarding the anthocyanin accumulation. mRNA levels of ADTs are dramatically increased in transgenic plants. ADT1/3 mutation greatly affects cold-induced anthocyanin accumulation. Single mutants have no obvious defects in plant growth compared with the wild-type, except for isozyme ADT2, whereas the adt4/5 double mutant and adt4/5 combined with other mutants including adt1, adt3, adt1/3, adt3/6, and adt1/3/6 display a dwarf phenotype. In all triple mutants, the mutants with adt1/3 produce the lowest levels of anthocyanin, about 40%-55% of wild-type, compared with other triple mutants such as adt1/4/5. Although the quintuple adt1/3/4/5/6 mutant produce the lowest level (about 35% of the wild-type level) of anthocyanin, no significant difference is detected between the quintuple and quadruple mutants (adt1/3/4/5, adt1/3/4/6, and adt1/3/5/6). The anthocyanin profile is not altered in adt mutants, the adt1/3/4/5/6 quintuple mutant still produces about 30% of wild-type anthocyanin content, overview
malfunction
ADT-deficient Arabidopsis thaliana mutants have significantly reduced lignin contents, with stronger reductions in lines that have deficiencies in more ADT isoforms, effects of the modulation of ADT on photosynthetic parameters and secondary metabolism, metabolomics, overview. A reduced carbon flux into L-Phe biosynthesis in ADT mutants impairs the consumption of photosynthetically produced ATP, leading to an increased ATP/ADP ratio, overaccumulation of transitory starch, and lower electron transport rates. The effect on electron transport rates is caused by an increase in proton motive force across the thylakoid membrane that downregulates photosystem II activity by the high-energy quenching mechanism. ADT mutants show reduced flavonoid, phenylpropanoid, lignan, and glucosinolate contents, including glucosinolates that are not derived from aromatic amino acids, and significantly increased contents of putative galactolipids and apocarotenoids. Concerning respiration and carbon fixation rates, ADT knockout mutant adt3/4/5/6 does reveal no significant difference in both night- and day-adapted plants. Transitory starch in chloroplasts might serve, at least in part, as an alternative carbon sink in ADT-deficient plants. In the adt3/4/5/6 knockout, the starch content is increased by more than 60%. Phenomics analysis with the adt3/4/5/6 mutant and metabolic analysis of rosette leaves
malfunction
ADT-deficient Arabidopsis thaliana mutants have significantly reduced lignin contents, with stronger reductions in lines that have deficiencies in more ADT isoforms, effects of the modulation of ADT on photosynthetic parameters and secondary metabolism, metabolomics, overview. A reduced carbon flux into Phe biosynthesis in ADT mutants impairs the consumption of photosynthetically produced ATP, leading to an increased ATP/ADP ratio, overaccumulation of transitory starch, and lower electron transport rates. The effect on electron transport rates is caused by an increase in proton motive force across the thylakoid membrane that downregulates photosystem II activity by the high-energy quenching mechanism. ADT mutants show reduced flavonoid, phenylpropanoid, lignan, and glucosinolate contents, including glucosinolates that are not derived from aromatic amino acids, and significantly increased contents of putative galactolipids and apocarotenoids. Concerning respiration and carbon fixation rates, ADT knockout mutant adt3/4/5/6 does reveal no significant difference in both night- and day-adapted plants. Transitory starch in chloroplasts might serve, at least in part, as an alternative carbon sink in ADT-deficient plants. In the adt3/4/5/6 knockout, the starch content is increased by more than 60%. Phenomics analysis with the adt3/4/5/6 mutant and metabolic analysis of rosette leaves
malfunction
ADT4/5 mutation greatly affects cold-induced anthocyanin accumulation. mRNA levels of ADTs are dramatically increased in transgenic plants. Single mutants have no obvious defects in plant growth compared with the wild-type, except for isozyme ADT2, whereas the adt4/5 double mutant and adt4/5 combined with other mutants including adt1, adt3, adt1/3, adt3/6, and adt1/3/6 display a dwarf phenotype. In all triple mutants, the mutants with adt1/3 produce the lowest levels of anthocyanin, about 40%-55% of wild-type, compared with other triple mutants such as adt1/4/5. Although the quintuple adt1/3/4/5/6 mutant produce the lowest level (about 35% of the wild-type level) of anthocyanin, no significant difference is detected between the quintuple and quadruple mutants (adt1/3/4/5, adt1/3/4/6, and adt1/3/5/6). The anthocyanin profile is not altered in adt mutants, the adt1/3/4/5/6 quintuple mutant still produces about 30% of wild-type anthocyanin content, overview. The leaves of ADT4/ADT5 overexpressing plants are yellow/white, narrow, small, and upwardly curled. Some ADT4/ADT5 overexpression lines are dwarf and sterile
malfunction
chloroplast morphology and FtsZ2-YFP localization is affected by a point mutation in ADT2 in mutant adt2-1D
malfunction
genome-wide proteomics of the adt3 mutant revealed a general downregulation of plastidic proteins and ROS-scavenging enzymes, corroborating the hypothesis that the ADT3 supply of Phe is required to control ROS concentration and distribution to protect cellular components. In addition, loss of ADT3 disrupts cotyledon epidermal patterning by affecting the number and expansion of pavement cells and stomata cell fate specification, severe alterations in mesophyll cells, which lack oil bodies and normal plastids, are observed. Loss of ADT3 disturbs epidermis development in the cotyledons of dark-grown seedlings. Mutant adt3 cotyledons exhibit abnormal subcellular features. Upregulation of the pathway leading to cuticle production is accompanied by an abnormal cuticle structure and/or deposition in the adt3 mutant. Such impairment results in an increase in cell permeability and provides a link to understand the cell defects in the adt3 cotyledon epidermis. Involvement of the cell wall in adt3 cell morphology, phenotype. The proteomic analysis reveals that adt3-1 mutation causes alteration of the expression of 1333 proteins, 608 of which are downregulated and 725 of which are upregulated, overview
malfunction
mRNA levels of ADTs ae dramatically increased in transgenic plants. Transgenic plants overexpressing ADT2 are very sensitive to L-Phe. Analysis of the role of ADT2 in anthocyanin biosynthesis of transgenic plants, designated adt2-amiR, in which expression of ADT2 is significantly downregulated by artificial microRNA interference, quantitative PCR analysis reveals that in the two adt2-amiR lines, the level of ADT2 mRNA is about 10% of the wild-type level, whereas expression of other ADTs is not dramatically altered despite statistically significant changes detected in some ADTs. Similar to other single mutants, adt2-amiR plants have no obvious phenotypes in growth compared with wild-type. The two adt2-amiR lines produce about 35% of wild-type anthocyanin content in the sucrose-induced system
malfunction
mRNA levels of ADTs are dramatically increased in transgenic plants. Single mutants have no obvious defects in plant growth compared with the wild-type, except for isozme ADT2, whereas the adt4/5 double mutant and adt4/5 combined with other mutants including adt1, adt3, adt1/3, adt3/6, and adt1/3/6 display a dwarf phenotype. In all triple mutants, the mutants with adt1/3 produce the lowest levels of anthocyanin, about 40%-55% of wild-type, compared with other triple mutants such as adt1/4/5. Although the quintuple adt1/3/4/5/6 mutant produce the lowest level (about 35% of the wild-type level) of anthocyanin, no significant difference is detected between the quintuple and quadruple mutants (adt1/3/4/5, adt1/3/4/6, and adt1/3/5/6). The anthocyanin profile is not altered in adt mutants, the adt1/3/4/5/6 quintuple mutant still produces about 30% of wild-type anthocyanin content, overview
malfunction
transgenic plants overexpressing ADT4, which appears to be less sensitive to L-Phe than plants overexpressing ADT2, hyperaccumulate Phe and produce elevated level of anthocyanins. ADT4/5 mutation greatly affects cold-induced anthocyanin accumulation. mRNA levels of ADTs are dramatically increased in transgenic plants. Single mutants have no obvious defects in plant growth compared with the wild-type, except for isozyme ADT2, whereas the adt4/5 double mutant and adt4/5 combined with other mutants including adt1, adt3, adt1/3, adt3/6, and adt1/3/6 display a dwarf phenotype. In all triple mutants, the mutants with adt1/3 produce the lowest levels of anthocyanin, about 40%-55% of wild-type, compared with other triple mutants such as adt1/4/5. Although the quintuple adt1/3/4/5/6 mutant produce the lowest level (about 35% of the wild-type level) of anthocyanin, no significant difference is detected between the quintuple and quadruple mutants (adt1/3/4/5, adt1/3/4/6, and adt1/3/5/6). The anthocyanin profile is not altered in adt mutants, the adt1/3/4/5/6 quintuple mutant still produces about 30% of wild-type anthocyanin content, overview. The leaves of ADT4/ADT5 overexpressing plants are yellow/white, narrow, small, and upwardly curled. Some ADT4/ADT5 overexpression lines are dwarf and sterile
malfunction
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chloroplast morphology and FtsZ2-YFP localization is affected by a point mutation in ADT2 in mutant adt2-1D
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metabolism
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Mtr1 encoding enzyme ADT/PDT catalyzes the final reaction in Phe biosynthesis and is critical for regulating the size of Phe pool in plant cells. Mtr1 callus contains a high level of secondary metabolites including phenylpropanoids and indole alkaloid, but these do not have a significant effect on the rest of the plant's morphological and other agronomic characteristics
metabolism
The final steps of phenylalanine biosynthesis in bacteria, fungi and plants can occur via phenylpyruvate or arogenate intermediates. These routes are determined by the presence of prephenate dehydratase, EC 4.2.1.51, which forms phenylpyruvate from prephenate, or arogenate dehydratase, which forms phenylalanine directly from arogenate
metabolism
arogenate dehydratase (ADT) catalyzes the final step of phenylalanine (Phe) biosynthesis, effects of the modulation of ADT on photosynthetic parameters and secondary metabolism, metabolomics, overview
physiological function
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the enzyme is required for biosynthesis of L-phenylalanine. Specific ADTs are differentially regulated so as to control Phe biosynthesis for protein synthesis versus its much more massive deployment for phenylpropanoid metabolism, overview
physiological function
all six ADT isoforms function redundantly in anthocyanin biosynthesis but have differential contributions. ADT isoforms regulate anthocyanin biosynthesis as well as lignin content and composition in a redundant and differential manner. ADT2 contributes the most to anthocyanin accumulation and plays the most important role in anthocyanin biosynthesis, followed by ADT1 and ADT3, and ADT4-ADT6. ADT4 and ADT5 play a dominant role in plant growth. ADT4-ADT6 act synergistically with ADT1 and ADT3 in anthocyanin biosynthesis. Anthocyanin content is positively correlated with the levels of Phe and sucrose-induced ADT transcripts in seedlings. Consistently, addition of Phe to the medium dramatically increases anthocyanin content in the wild-type plants. The level of Phe is an important regulatory factor for sustaining anthocyanin biosynthesis. Anthocyanins are a class of water-soluble flavonoid pigments synthesized from Phe in higher plants. They have important biological functions, including defense against UV-B radiation, attracting pollinators and scavenging reactive oxygen species. ADT4 and ADT5 may not be allosterically regulated by the product Phe, ADT4 is not feedback regulated by Phe
physiological function
all six ADT isoforms function redundantly in anthocyanin biosynthesis but have differential contributions. ADT isoforms regulate anthocyanin biosynthesis as well as lignin content and composition in a redundant and differential manner. ADT2 contributes the most to anthocyanin accumulation and plays the most important role in anthocyanin biosynthesis, followed by ADT1 and ADT3, and ADT4-ADT6. ADT4 and ADT5 play a dominant role in plant growth. ADT4-ADT6 act synergistically with ADT1 and ADT3 in anthocyanin biosynthesis. Anthocyanin content is positively correlated with the levels of Phe and sucrose-induced ADT transcripts in seedlings. Consistently, addition of Phe to the medium dramatically increases anthocyanin content in the wild-type plants. The level of Phe is an important regulatory factor for sustaining anthocyanin biosynthesis. Anthocyanins are a class of water-soluble flavonoid pigments synthesized from Phe in higher plants. They have important biological functions, including defense against UV-B radiation, attracting pollinators and scavenging reactive oxygen species. ADT4 and ADT5 may not be allosterically regulated by the product Phe
physiological function
all six ADT isoforms function redundantly in anthocyanin biosynthesis but have differential contributions. ADT isoforms regulate anthocyanin biosynthesis as well as lignin content and composition in a redundant and differential manner. ADT2 contributes the most to anthocyanin accumulation and plays the most important role in anthocyanin biosynthesis, followed by ADT1 and ADT3, and ADT4-ADT6. ADT4 and ADT5 play a dominant role in plant growth. ADT4-ADT6 act synergistically with ADT1 and ADT3 in anthocyanin biosynthesis. Anthocyanin content is positively correlated with the levels of Phe and sucrose-induced ADT transcripts in seedlings. Consistently, addition of Phe to the medium dramatically increases anthocyanin content in the wild-type plants. The level of Phe is an important regulatory factor for sustaining anthocyanin biosynthesis. Anthocyanins are a class of water-soluble flavonoid pigments synthesized from Phe in higher plants. They have important biological functions, including defense against UV-B radiation, attracting pollinators and scavenging reactive oxygen species
physiological function
all six ADT isoforms function redundantly in anthocyanin biosynthesis but have differential contributions. ADT isoforms regulate anthocyanin biosynthesis as well as lignin content and composition in a redundant and differential manner. ADT2 contributes the most to anthocyanin accumulation and plays the most important role in anthocyanin biosynthesis, followed by ADT1 and ADT3, and ADT4-ADT6. ADT4 and ADT5 play a dominant role in plant growth. ADT4-ADT6 act synergistically with ADT1 and ADT3 in anthocyanin biosynthesis. Anthocyanin content is positively correlated with the levels of Phe and sucrose-induced ADT transcripts in seedlings. Consistently, addition of Phe to the medium dramatically increases anthocyanin content in the wild-type plants. The level of Phe is an important regulatory factor for sustaining anthocyanin biosynthesis. Anthocyanins are a class of water-soluble flavonoid pigments synthesized from Phe in higher plants. They have important biological functions, including defense against UV-B radiation, attracting pollinators and scavenging reactive oxygen species. ADT2 is feedback regulated by L-Phe
physiological function
arogenate dehydratase3, ADT3, plays a critical role for the phenylalanine (Phe) biosynthetic activity coordinating reactive oxygen species (ROS) homeostasis and cotyledon development in etiolated Arabidopsis thaliana seedlings. Isozyme ADT3 is expressed in the cotyledon and shoot apical meristem, mainly in the cytosol, the epidermis of adt3 cotyledons contains higher levels of ROS. L-Phe might play an additional role in supplying nutrients to the young seedling. ADT3 accumulates in the cytosol and is required to maintain ROS homeostasis
additional information
ADT2 forms structures consistent with chloroplast division rings
additional information
ADT2 forms structures consistent with chloroplast division rings
additional information
ADT2 forms structures consistent with chloroplast division rings
additional information
ADT2 forms structures consistent with chloroplast division rings
additional information
ADT2 forms structures consistent with chloroplast division rings
additional information
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ADT2 forms structures consistent with chloroplast division rings
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