Temporally distinct accumulation of transcripts encoding enzymes of the prechorismate pathway in elicitor-treated, cultured tomato cells.

Görlach, Jörn; Raesecke, Hans-Rudiger; Rentsch, Doris; Regenass, Martin; Roy, Philippe; Zala, Marcello; Keel, Christoph; Boller, Thomas; Amrhein, Nikolaus; Schmid, Jürg

doi:10.1073/pnas.92.8.3166

Cited by 83 publications

(80 citation statements)

References 27 publications

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“…In agreement with the latter possibility, G€ orlach et al (1995) suggested that the increased demand for phenylalanine in the phenylpropanoid pathway after elicitor treatment increased de novo synthesis of phenylanine biosynthesis. 38 Our results together with Slisz's observation suggested that phenylalanine may play an important role in citrus response to CLas.…”

Section: Discussionmentioning

confidence: 48%

Amino acids implicated in plantdefenseare higher inCandidatusLiberibacter asiaticus-tolerant citrus varieties

Killiny

Hijaz

2016

Plant Signaling & Behavior

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Citrus Huanglongbing (HLB), also known as citrus greening, has been threatening the citrus industry since the early 1900's and up to this date there are no effective cures for this disease. Field observations and greenhouse controlled studies demonstrated that some citrus genotypes are more tolerant to Candidatus Liberibacter asiaticus (CLas) pathogen than others. However, the mechanisms underpinning tolerance has not been determined yet. The phloem sap composition of CLas-tolerant and sensitive citrus varieties was studied to identify metabolites that could be responsible for their tolerance to CLas. The citrus phloem sap was collected by centrifugation and was analyzed with gas chromatography-mass spectrometry after methyl chloroformate derivatization. Thirty-three metabolites were detected in the phloem sap of the studied varieties: twenty 20 amino acids, eight 8 organic acids, and five 5 fatty acids. Interestingly, the levels of most amino acids, especially those implicated in plantdefense to pathogens such as phenylalanine, tyrosine, tryptophan, lysine, and asparagine were higher in tolerant varieties. Although the level of organic acids varied between cultivars, this variation was not correlated with citrus resistance to CLas and could be cultivar specific. The fatty acids were found in trace amounts and in most cases their levels were not significantly different among varieties. Better understanding of the mechanisms underpinning citrus tolerance to CLas will help in developing economically tolerant varieties.

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Section: Discussionmentioning

confidence: 48%

Amino acids implicated in plantdefenseare higher inCandidatusLiberibacter asiaticus-tolerant citrus varieties

Killiny

Hijaz

2016

Plant Signaling & Behavior

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“…The aromatic precursor HGA is derived from prephenate or Tyr, both products of the shikimate pathway (Threlfall and Whistance, 1971;Fiedler et al, 1982;Lopukhina et al, 2001;Sandorf and Hollander-Czytko, 2002). In plants, the shikimate pathway has been shown to be regulated at the transcriptional level and globally up-regulated during biotic and abiotic stresses (Gorlach et al, 1995;Herrman and Weaver, 1999;Diaz et al, 2001). Thus, the shikimate pathway may provide an increased pool of prephenate that is at least partially used for elevated tocopherol synthesis in stressed plants.…”

Section: Discussionmentioning

confidence: 99%

The Role of Homogentisate Phytyltransferase and Other Tocopherol Pathway Enzymes in the Regulation of Tocopherol Synthesis during Abiotic Stress

2003

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Tocopherols are amphipathic antioxidants synthesized exclusively by photosynthetic organisms. Tocopherol levels change significantly during plant growth and development and in response to stress, likely as a consequence of the altered expression of pathway-related genes. Homogentisate phytyltransferase (HPT) is a key enzyme limiting tocopherol biosynthesis in unstressed Arabidopsis leaves (E. Collakova, D. DellaPenna [2003] Plant Physiol 131: 632-642). Wild-type and transgenic Arabidopsis plants constitutively overexpressing HPT (35S::HPT1) were subjected to a combination of abiotic stresses for up to 15 d and tocopherol levels, composition, and expression of several tocopherol pathway-related genes were determined. Abiotic stress resulted in an 18-and 8-fold increase in total tocopherol content in wild-type and 35S::HPT1 leaves, respectively, with tocopherol levels in 35S::HPT1 being 2-to 4-fold higher than wild type at all experimental time points. Increased total tocopherol levels correlated with elevated HPT mRNA levels and HPT specific activity in 35S::HPT1 and wild-type leaves, suggesting that HPT activity limits total tocopherol synthesis during abiotic stress. In addition, substrate availability and expression of pathway enzymes before HPT also contribute to increased tocopherol synthesis during stress. The accumulation of high levels of ␤-, ␥-, and ␦-tocopherols in stressed tissues suggested that the methylation of phytylquinol and tocopherol intermediates limit ␣-tocopherol synthesis. Overexpression of ␥-tocopherol methyltransferase in the 35S::HPT1 background resulted in nearly complete conversion of ␥-and ␦-tocopherols to ␣-and ␤-tocopherols, respectively, indicating that ␥-tocopherol methyltransferase activity limits ␣-tocopherol synthesis in stressed leaves.Tocopherols are a group of lipid soluble antioxidants collectively known as vitamin E that are essential components of animal diets. Dietary vitamin E is required for maintaining proper muscular, immune, and neural function and may be involved in reducing the risk of cancer, cardiovascular disease, and cataracts in humans (Pryor, 2000;Brigelius-Flohe et al., 2002). In plants, tocopherols are believed to protect chloroplast membranes from photooxidation and help to provide an optimal environment for the photosynthetic machinery (Fryer, 1992;Munne-Bosch and Alegre, 2002a). Many of the proposed tocopherol functions in animals and plants are related to their antioxidant properties, the most prominent of which is protection of polyunsaturated fatty acids from lipid peroxidation by quenching and scavenging various reactive oxygen species (ROS) including singlet oxygen, superoxide radicals, and alkyl peroxy radicals (Fukuzawa and Gebicky, 1983;Munne-Bosch and Alegre, 2002a).Tocopherols are only synthesized by photosynthetic organisms and consist of a polar chromanol ring and a 15-carbon lipophilic prenyl chain derived from homogentisic acid (HGA) and phytyl diphosphate (PDP; Fig. 1). In plants, HGA is formed from p-hydroxyphenyl pyruvate (HPP) by the c...

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“…DAHP synthase catalyzes the entry step of the shikimate pathway and in microorganisms is regulated transcriptionally and is also subjected to feedback regulation by Phe at the enzyme level (Bentley, 1990;Herrmann and Weaver, 1999). In plants, DAHP synthase genes are transcriptionally regulated and induced in response to various environmental stimuli (Dyer et al, 1989;Keith et al, 1991;Gö rlach et al, 1995). At the enzyme level, however, all plant DAHP synthases examined to date are insensitive to Phe (Huisman and Kosuge, 1974;Suzich et al, 1985;Herrmann, 1995).…”

Section: Regulation Of the Shikimate Pathway Leading To Phe Biosynthesismentioning

confidence: 99%

RNAi Suppression of Arogenate Dehydratase1 Reveals That Phenylalanine Is Synthesized Predominantly via the Arogenate Pathway in Petunia Petals

et al. 2010

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L-Phe, a protein building block and precursor of numerous phenolic compounds, is synthesized from prephenate via an arogenate and/or phenylpyruvate route in which arogenate dehydratase (ADT) or prephenate dehydratase, respectively, plays a key role. Here, we used Petunia hybrida flowers, which are rich in Phe-derived volatiles, to determine the biosynthetic routes involved in Phe formation in planta. Of the three identified petunia ADTs, expression of ADT1 was the highest in petunia petals and positively correlated with endogenous Phe levels throughout flower development. ADT1 showed strict substrate specificity toward arogenate, although with the lowest catalytic efficiency among the three ADTs. ADT1 suppression via RNA interference in petunia petals significantly reduced ADT activity, levels of Phe, and downstream phenylpropanoid/benzenoid volatiles. Unexpectedly, arogenate levels were unaltered, while shikimate and Trp levels were decreased in transgenic petals. Stable isotope labeling experiments showed that ADT1 suppression led to downregulation of carbon flux toward shikimic acid. However, an exogenous supply of shikimate bypassed this negative regulation and resulted in elevated arogenate accumulation. Feeding with shikimate also led to prephenate and phenylpyruvate accumulation and a partial recovery of the reduced Phe level in transgenic petals, suggesting that the phenylpyruvate route can also operate in planta. These results provide genetic evidence that Phe is synthesized predominantly via arogenate in petunia petals and uncover a novel posttranscriptional regulation of the shikimate pathway.

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Temporally distinct accumulation of transcripts encoding enzymes of the prechorismate pathway in elicitor-treated, cultured tomato cells.

Cited by 83 publications

References 27 publications

Amino acids implicated in plantdefenseare higher inCandidatusLiberibacter asiaticus-tolerant citrus varieties

Amino acids implicated in plantdefenseare higher inCandidatusLiberibacter asiaticus-tolerant citrus varieties

The Role of Homogentisate Phytyltransferase and Other Tocopherol Pathway Enzymes in the Regulation of Tocopherol Synthesis during Abiotic Stress

RNAi Suppression of Arogenate Dehydratase1 Reveals That Phenylalanine Is Synthesized Predominantly via the Arogenate Pathway in Petunia Petals

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