Hormonal Regulation of Organic and Phosphoric Acid Release by Barley Aleurone Layers and Scutella

Drozdowicz, Yolanda M.; Jones, Russell L.

doi:10.1104/pp.108.2.769

Cited by 36 publications

(29 citation statements)

References 39 publications

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“…Because the pK a for HNO 2 is 3.2, this mechanism for NO synthesis is unlikely to occur in the cytosol of plant cells because the pH of the cytoplasm effectively prevents the formation of HNO 2 (Yamasaki, 2000). It seemed possible to us, however, that NO could be produced in the apoplast by this mechanism given that (1) the apoplast is acidic (Drozdowicz and Jones, 1995;Yu et al, 2000;Fasano et al, 2001); (2) nitrite is present in the apoplast of some plant tissues, and nitritepermeable transporters are found on the plasma membrane of plant cells (Aslam et al, 1994); and (3) the redox status of the apoplast is regulated, and antioxidants in their reduced form are found in the apoplast (Horemans et al, 2000). We tested the hypothesis that NO is synthesized nonenzymatically by the chemical reduction of NO 2 ÿ in the apoplast of Hordeum vulgare cv Himalaya (barley) aleurone layers.…”

Section: Introductionmentioning

confidence: 86%

Apoplastic Synthesis of Nitric Oxide by Plant Tissues

2004

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Nitric oxide (NO) is an important signaling molecule in animals and plants. In mammals, NO is produced from Arg by the enzyme NO synthase. In plants, NO synthesis from Arg using an NO synthase-type enzyme and from nitrite using nitrate reductase has been demonstrated previously. The data presented in this report strongly support the hypothesis that plant tissues also synthesize NO via the nonenzymatic reduction of apoplastic nitrite. As measured by mass spectrometry or an NO-reactive fluorescent probe, Hordeum vulgare (barley) aleurone layers produce NO rapidly when nitrite is added to the medium in which they are incubated. NO production requires an acid apoplast and is accompanied by a loss of nitrite from the medium. Phenolic compounds in the medium can increase the rate of NO production. The possible significance of apoplastic NO production for germinating grain and for plant roots is discussed.

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Section: Introductionmentioning

confidence: 86%

Apoplastic Synthesis of Nitric Oxide by Plant Tissues

2004

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“…The enzyme has also been implicated in the acidification and malate accumulation processes during maturation, but not germination, of barley grain (Macnicol et al, 1992;Drozdowicz and Jones, 1995). PEPC activity increases during germination of Ricinus communis (Sangwan et al, 1992;Plaxton, 1994a, 1994b) and Sorghum seeds (Khayat et al, 1991).…”

Section: Dlscusslonmentioning

confidence: 99%

In Vivo and in Vitro Phosphorylation of the Phosphoenolpyruvate Carboxylase from Wheat Seeds during Germination

et al. 1996

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Phosphoenolpyruvate carboxylase (PEPC) activity was detected in the aleurone endosperm of wheat (Triticum aestivum cv Chinese Spring) seeds, and specific anti-Sorghum C, PEPC polyclonal antibodies cross-reacted with 103-and 100-kD polypeptides present in dry seeds and seeds that had imbibed; in addition, a new, 108-kD polypeptide was detected 6 h after imbibition. l h e use of specific anti-phosphorylation-site immunoglobulin C (APS-lgC) identified the presence of a phosphorylation motif equivalent to that found in other plant PEPCs studied so far. The binding of this APS-lgC to the target protein promoted changes in the properties of seed PEPC similar to those produced by phosphorylation, as previously shown for the recombinant Sorghum leaf C, PEPC. In desalted seed extracts, an endogenous PEPC kinase activity catalyzed a bona fide phosphorylation of the target protein, as deduced from the immunoinhibition of the in vitro phosphorylation reaction by the APSIgC. In addition, the major, 103-kD PEPC polypeptide was also shown to be radiolabeled in situ 48 h after imbibition in [32Plorthophosphate. The ratio between optimal (pH 8) and suboptimal (pH 7.3 or 7.1) PEPC activity decreased during germination, thereby suggesting a change in catalytic rate related to an in vivo phosphorylation process. These collective data document that the components needed for the regulatory phosphorylation of PEPC are present and functional during germination of wheat seeds.

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“…) by Drozdowicz and Jones (1995). Since the kinase IC 50 for L-malate was found to be around 0.5 mM (Fig.…”

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confidence: 99%

Regulation of Phosphoenolpyruvate Carboxylase Phosphorylation by Metabolites and Abscisic Acid during the Development and Germination of Barley Seeds

et al. 2008

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During barley (Hordeum vulgare) seed development, phosphoenolpyruvate carboxylase (PEPC) activity increased and PEPCspecific antibodies revealed housekeeping (103-kD) and inducible (108-kD) subunits. Bacterial-type PEPC fragments were immunologically detected in denatured protein extracts from dry and imbibed conditions; however, on nondenaturing gels, the activity of the recently reported octameric PEPC (in castor [Ricinus communis] oil seeds) was not detected. The phosphorylation state of the PEPC, as judged by L-malate 50% inhibition of initial activity values, phosphoprotein chromatography, and immunodetection of the phosphorylated N terminus, was found to be high between 8 and 18 d postanthesis (DPA) and during imbibition. In contrast, the enzyme appeared to be in a low phosphorylation state from 20 DPA up to dry seed. The time course of 32/36-kD, Ca 2+ -independent PEPC kinase activity exhibited a substantial increase after 30 DPA that did not coincide with the PEPC phosphorylation profile. This kinase was found to be inhibited by L-malate and not by putative protein inhibitors, and the PEPC phosphorylation status correlated with high glucose-6-phosphate to malate ratios, thereby suggesting an in vivo metabolic control of the kinase. PEPC phosphorylation was also regulated by photosynthate supply at 11 DPA. In addition, when fed exogenously to imbibing seeds, abscisic acid significantly increased PEPC kinase activity. This was further enhanced by the cytosolic protein synthesis inhibitor cycloheximide but blocked by protease inhibitors, thereby suggesting that the phytohormone acts on the stability of the kinase. We propose that a similar abscisic acid-dependent effect may contribute to produce the increase in PEPC kinase activity during desiccation stages.

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Hormonal Regulation of Organic and Phosphoric Acid Release by Barley Aleurone Layers and Scutella

Cited by 36 publications

References 39 publications

Apoplastic Synthesis of Nitric Oxide by Plant Tissues

Apoplastic Synthesis of Nitric Oxide by Plant Tissues

In Vivo and in Vitro Phosphorylation of the Phosphoenolpyruvate Carboxylase from Wheat Seeds during Germination

Regulation of Phosphoenolpyruvate Carboxylase Phosphorylation by Metabolites and Abscisic Acid during the Development and Germination of Barley Seeds

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