Redox regulation of free amino acid levels in Arabidopsis thaliana

Abstract

Abiotic stresses induce oxidative stress, which modifies the level of several metabolites including amino acids. The redox control of free amino acid profile was monitored in wild type and ascorbate or glutathione deficient mutant Arabidopsis plants before and after hydroponic treatment with various redox agents. Both mutations and treatments modified the size and redox state of the ascorbate (AsA) and/or glutathione (GSH) pools. The total free amino acid content was increased by AsA, GSH and H 2 O 2 in all 3 genotypes and a very large (3-fold) increase was observed in the GSH-deficient pad2-1 mutant after GSH treatment compared to the untreated wild type plants. Addition of GSH reduced the ratio of amino acids belonging to the glutamate family on a large scale and increased the relative amount of non-proteinogenic amino acids. The latter change was due to the large increase in the content of alpha-aminoadipate, an inhibitor of Glu transport. Most of the treatments increased the Pro content, which effect was due to the activation of genes involved in Pro synthesis. Although all studied redox compounds influenced the amount of free amino acids and a mostly positive, very close (r>0.9) correlation exists between these parameters, a special regulatory role of GSH could be presumed due to its more powerful effect. This may originate from the thiol/disulphide conversion or (de)glutathionylation of enzymes participating in the amino acid metabolism.Abbreviations -Aaa, α-aminoadipic acid; AsA, ascorbic acid; Cysta, cystathione; DHA, dehydroascorbate; DTT, dithiotreitol; GSH, glutathione; GSSG, glutathione disulphide; NPPAs, nonproteogenic amino acids; OAT, ornithine aminotransferase; PDH, proline dehydrogenase; P5CR, pyrroline-5-carboxylate reductase; P5CDH, delta-1-pyrroline-5-carboxylate dehydrogenase; P5CS1, delta This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/ppl.12510 This article is protected by copyright. All rights reserved. Accepted Article1-pyrroline-5-carboxylate synthase 1; P5CS2, delta 1-pyrroline-5-carboxylate synthase 2. IntroductionRedox status has a major role in the regulation of metabolism and is controlled by metabolic processes at the same time (Geigenberger and Fernie 2014). The proper redox status during growth and development under optimal and adverse environmental conditions is maintained by the antioxidant system through the removal of the excess of reactive oxygen species (ROS; Dietz 2008, Suzuki et al. 2012, Kocsy et al. 2013, Considine and Foyer 2014. Accumulation of ROS, such as superoxide radical, hydrogen peroxide, hydroxyl radical and singlet oxygen in high concentration may cause serious injuries or even plant lethality under stress conditions (Bartosz 1997). However, a moderate increase in ROS content may have positive functions as well since, ...

Light intensity and spectrum affect metabolism of glutathione and amino acids at transcriptional level

“…The effect of light on the free amino acid metabolism may be mediated by the GSH-dependent redox changes since a negative correlation was observed between the percentage of GSSG and transcript levels of the related genes (S3 Table). In addition, similar differences were observed in GSH and free amino acid levels between the plants grown under various light conditions (Figs 3 and 5) which results are in close agreement with earlier observations about the redox regulation of amino acid accumulation obtained in Arabidopsis [32]. Treatment of wild type and mutant plants deficient in AsA or GSH with GSH, AsA, dithiothreitol (DTT) and H 2 O 2 clearly showed the redox control of the free amino acid concentrations since addition of these compounds could compensate the effect of mutations.…”

“…For the analysis of free amino acids, leaf samples of 300 mg fresh weight were extracted with 2 ml cold 10% trichloroacetic acid as described by Gulyás et al [32]. The free amino acids were detected by an automatic amino acid analyser (Ingos Ltd., Czech Republic) equipped with an Ionex Ostion LCP5020 cation-exchange column (22 × 0.37 cm).…”

Source and sink mechanisms of nitrogen transport and use

“…Transporter expression was found to be cell-and tissue-specific, developmentally regulated, and affected by abiotic or biotic factors such as N, light, salt and drought stress, and nematode or pathogen attack (Pratelli & Pilot, 2014;Hav e et al, 2016;Perchlik & Tegeder, 2017). Changes in the redox status or other endogenous factors may induce the transcriptional changes (Geigenberger & Fernie, 2014;Noctor et al, 2015;Bellegarde et al, 2017;Gulyas et al, 2017). Cis-regulatory elements were identified in the 5 0untranslated region of rice OsAAP6 that seem to be responsible for transcriptional activation.…”

Role of light‐intensity‐dependent changes in thiol and amino acid metabolism in the adaptation of wheat to drought

“…Light-intensity-dependent changes in photosynthesis and consequently in ROS and antioxidants may result in coordinated changes in the whole metabolism. Correspondingly, redox-dependent adjustment of amino acid metabolism was shown in Arabidopsis (Gulyás, 2017). Certain amino acids in turn ensure a connection to the redox system.…”