Juan C. Begara-Morales

Bio: Juan C. Begara-Morales is an academic researcher from University of Jaén. The author has contributed to research in topics: Reactive nitrogen species & Abiotic stress. The author has an hindex of 25, co-authored 52 publications receiving 2651 citations. Previous affiliations of Juan C. Begara-Morales include Spanish National Research Council.

Metabolism of reactive nitrogen species in pea plants under abiotic stress conditions.

Abstract: Nitric oxide (*NO) is a key signaling molecule in different physiological processes of animals and plants. However, little is known about the metabolism of endogenous *NO and other reactive nitrogen species (RNS) in plants under abiotic stress conditions. Using pea plants exposed to six different abiotic stress conditions (high light intensity, low and high temperature, continuous light, continuous dark and mechanical wounding), several key components of the metabolism of RNS including the content of *NO, S-nitrosothiols (RSNOs) and nitrite plus nitrate, the enzyme activities of l-arginine-dependent nitric oxide synthase (NOS) and S-nitrosogluthathione reductase (GSNOR), and the profile of protein tyrosine nitration (NO(2)-Tyr) were analyzed in leaves. Low temperature was the stress that produced the highest increase of NOS and GSNOR activities, and this was accompanied by an increase in the content of total *NO and S-nitrosothiols, and an intensification of the immunoreactivity with an antibody against NO(2)-Tyr. Mechanical wounding, high temperature and light also had a clear activating effect on the different indicators of RNS metabolism in pea plants. However, the total content of nitrite and nitrate in leaves was not affected by any of these stresses. Considering that protein tyrosine nitration is a potential marker of nitrosative stress, the results obtained suggest that low and high temperature, continuous light and high light intensity are abiotic stress conditions that can induce nitrosative stress in pea plants.

Dual regulation of cytosolic ascorbate peroxidase (APX) by tyrosine nitration and S-nitrosylation

Abstract: Post-translational modifications (PTMs) mediated by nitric oxide (NO)-derived molecules have become a new area of research, as they can modulate the function of target proteins. Proteomic data have shown that ascorbate peroxidase (APX) is one of the potential targets of PTMs mediated by NO-derived molecules. Using recombinant pea cytosolic APX, the impact of peroxynitrite (ONOO-) and S-nitrosoglutathione (GSNO), which are known to mediate protein nitration and S-nitrosylation processes, respectively, was analysed. While peroxynitrite inhibits APX activity, GSNO enhances its enzymatic activity. Mass spectrometric analysis of the nitrated APX enabled the determination that Tyr5 and Tyr235 were exclusively nitrated to 3-nitrotyrosine by peroxynitrite. Residue Cys32 was identified by the biotin switch method as S-nitrosylated. The location of these residues on the structure of pea APX reveals that Tyr235 is found at the bottom of the pocket where the haem group is enclosed, whereas Cys32 is at the ascorbate binding site. Pea plants grown under saline (150 mM NaCl) stress showed an enhancement of both APX activity and S-nitrosylated APX, as well as an increase of H2O2, NO, and S-nitrosothiol (SNO) content that can justify the induction of the APX activity. The results provide new insight into the molecular mechanism of the regulation of APX which can be both inactivated by irreversible nitration and activated by reversible S-nitrosylation.

Involvement of Reactive Nitrogen and Oxygen Species (RNS and ROS) in Sunflower–Mildew Interaction

Abstract: Nitric oxide (.NO) has been shown to participate in plant response against pathogen infection; however, less is known of the participation of other NO-derived molecules designated as reactive nitrogen species (RNS). Using two sunflower (Helianthus annuus L.) cultivars with different sensitivity to infection by the pathogen Plasmopara halstedii, we studied key components involved in RNS and ROS metabolism. We analyzed the superoxide radical production, hydrogen peroxide content, l-arginine-dependent nitric oxide synthase (NOS) and S-nitrosoglutathione reductase (GSNOR) activities. Furthermore, we examined the location and contents of .NO, S-nitrosothiols (RSNOs), S-nitrosoglutathione (GSNO) and protein 3-nitrotyrosine (NO(2)-Tyr) by confocal laser scanning microscopy (CLSM) and biochemical analyses. In the susceptible cultivar, the pathogen induces an increase in proteins that undergo tyrosine nitration accompanied by an augmentation in RSNOs. This rise of RSNOs seems to be independent of the enzymatic generation of .NO because the l-arginine-dependent NOS activity is reduced after infection. These results suggest that pathogens induce nitrosative stress in susceptible cultivars. In contrast, in the resistant cultivar, no increase of RSNOs or tyrosine nitration of proteins was observed, implying an absence of nitrosative stress. Therefore, it is proposed that the increase of tyrosine nitration of proteins can be considered a general biological marker of nitrosative stress in plants under biotic conditions.

Protein tyrosine nitration in pea roots during development and senescence

Abstract: Protein tyrosine nitration is a post-translational modification mediated by reactive nitrogen species (RNS) that is associated with nitro-oxidative damage. No information about this process is available in relation to higher plants during development and senescence. Using pea plants at different developmental stages (ranging from 8 to 71 days), tyrosine nitration in the main organs (roots, stems, leaves, flowers, and fruits) was analysed using immunological and proteomic approaches. In the roots of 71-day-old senescent plants, nitroproteome analysis enabled the identification a total of 16 nitrotyrosine-immunopositive proteins. Among the proteins identified, NADP-isocitrate dehydrogenase (ICDH), an enzyme involved in the carbon and nitrogen metabolism, redox regulation, and responses to oxidative stress, was selected to evaluate the effect of nitration. NADP-ICDH activity fell by 75% during senescence. Analysis showed that peroxynitrite inhibits recombinant cytosolic NADP-ICDH activity through a process of nitration. Of the 12 tyrosines present in this enzyme, mass spectrometric analysis of nitrated recombinant cytosolic NADP-ICDH enabled this study to identify the Tyr392 as exclusively nitrated by peroxynitrite. The data as a whole reveal that protein tyrosine nitration is a nitric oxide-derived PTM prevalent throughout root development and intensifies during senescence.

Protein targets of tyrosine nitration in sunflower (Helianthus annuus L.) hypocotyls

Abstract: Tyrosine nitration is recognized as an important post-translational protein modification in animal cells that can be used as an indicator of a nitrosative process. However, in plant systems, there is scant information on proteins that undergo this process. In sunflower hypocotyls, the content of tyrosine nitration (NO(2)-Tyr) and the identification of nitrated proteins were studied by high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) and proteomic approaches, respectively. In addition, the cell localization of nitrotyrosine proteins and peroxynitrite were analysed by confocal laser-scanning microscopy (CLSM) using antibodies against 3-nitrotyrosine and 3'-(p-aminophenyl) fluorescein (APF) as the fluorescent probe, in that order. The concentration of Tyr and NO(2)-Tyr in hypocotyls was 0.56 micromol mg(-1) protein and 0.19 pmol mg(-1) protein, respectively. By proteomic analysis, a total of 21 nitrotyrosine-immunopositive proteins were identified. These targets include proteins involved in photosynthesis, and in antioxidant, ATP, carbohydrate, and nitrogen metabolism. Among the proteins identified, S-adenosyl homocysteine hydrolase (SAHH) was selected as a model to evaluate the effect of nitration on SAHH activity using SIN-1 (a peroxynitrite donor) as the nitrating agent. When the hypocotyl extracts were exposed to 0.5 mM, 1 mM, and 5 mM SIN-1, the SAHH activity was inhibited by some 49%, 89%, and 94%, respectively. In silico analysis of the barley SAHH sequence, characterized Tyr448 as the most likely potential target for nitration. In summary, the present data are the first in plants concerning the content of nitrotyrosine and the identification of candidates of protein nitration. Taken together, the results suggest that Tyr nitration occurs in plant tissues under physiological conditions that could constitute an important process of protein regulation in such a way that, when it is overproduced in adverse circumstances, it can be used as a marker of nitrosative stress.

Mechanism of Salinity Tolerance in Plants: Physiological, Biochemical, and Molecular Characterization

Abstract: Salinity is a major abiotic stress limiting growth and productivity of plants in many areas of the world due to increasing use of poor quality of water for irrigation and soil salinization. Plant adaptation or tolerance to salinity stress involves complex physiological traits, metabolic pathways, and molecular or gene networks. A comprehensive understanding on how plants respond to salinity stress at different levels and an integrated approach of combining molecular tools with physiological and biochemical techniques are imperative for the development of salt-tolerant varieties of plants in salt-affected areas. Recent research has identified various adaptive responses to salinity stress at molecular, cellular, metabolic, and physiological levels, although mechanisms underlying salinity tolerance are far from being completely understood. This paper provides a comprehensive review of major research advances on biochemical, physiological, and molecular mechanisms regulating plant adaptation and tolerance to salinity stress.

Elucidating the molecular mechanisms mediating plant salt-stress responses

Abstract: Contents Summary 523 I. Introduction 523 II. Sensing salt stress 524 III. Ion homeostasis regulation 524 IV. Metabolite and cell activity responses to salt stress 527 V. Conclusions and perspectives 532 Acknowledgements 533 References 533 SUMMARY: Excess soluble salts in soil (saline soils) are harmful to most plants. Salt imposes osmotic, ionic, and secondary stresses on plants. Over the past two decades, many determinants of salt tolerance and their regulatory mechanisms have been identified and characterized using molecular genetics and genomics approaches. This review describes recent progress in deciphering the mechanisms controlling ion homeostasis, cell activity responses, and epigenetic regulation in plants under salt stress. Finally, we highlight research areas that require further research to reveal new determinants of salt tolerance in plants.

Regulation of Ascorbate-Glutathione Pathway in Mitigating Oxidative Damage in Plants under Abiotic Stress

Abstract: Reactive oxygen species (ROS) generation is a usual phenomenon in a plant both under a normal and stressed condition. However, under unfavorable or adverse conditions, ROS production exceeds the capacity of the antioxidant defense system. Both non-enzymatic and enzymatic components of the antioxidant defense system either detoxify or scavenge ROS and mitigate their deleterious effects. The Ascorbate-Glutathione (AsA-GSH) pathway, also known as Asada–Halliwell pathway comprises of AsA, GSH, and four enzymes viz. ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase, play a vital role in detoxifying ROS. Apart from ROS detoxification, they also interact with other defense systems in plants and protect the plants from various abiotic stress-induced damages. Several plant studies revealed that the upregulation or overexpression of AsA-GSH pathway enzymes and the enhancement of the AsA and GSH levels conferred plants better tolerance to abiotic stresses by reducing the ROS. In this review, we summarize the recent progress of the research on AsA-GSH pathway in terms of oxidative stress tolerance in plants. We also focus on the defense mechanisms as well as molecular interactions.

Importance of the Support Properties for Immobilization or Purification of Enzymes

Abstract: We gratefully recognize the support from the Spanish Government, CTQ2013-41507-R, Colciencia (Colombia) and CNPq (Brazil). The predoctoral fellowships for Mr dos Santos (CNPq, Brazil) are also recognized. A. Berenguer-Murcia thanks the Spanish Ministerio de Ciencia e Innovaciun for a Ramon y Cajal fellowship (RyC-2009-03813).

Nitric Reductase-Dependent Nitric Oxide Production Is Involved in Cold Acclimation and Freezing Tolerance in Arabidopsis

Abstract: Nitric oxide (NO) is an important signaling molecule involved in many physiological processes in plants. We evaluated the role of NO in cold acclimation and freezing tolerance using Arabidopsis (Arabidopsis thaliana) wild type and mutants nia1nia2 (for nitrate reductase [NR]-defective double mutant) and Atnoa1/rif1 (for nitric oxide associated1/resistant to inhibition by fosmidomycin1) that exhibit defects in NR and reduced NO production, respectively. Cold acclimation induced an increase in endogenous NO production in wild-type and Atnoa1/rif1 leaves, while endogenous NO level in nia1nia2 leaves was lower than in wild-type ones and was little changed during cold acclimation. Cold acclimation stimulated NR activity and induced up-regulation of NIA1 gene expression. In contrast, cold acclimation reduced the quantity of NOA1/RIF1 protein and inhibited NO synthase (NOS) activity. These results indicate that up-regulation of NR-dependent NO synthesis underpins cold acclimation-induced NO production. Seedlings of nia1nia2 were less tolerant to freezing than wild-type plants. Pharmacological studies using NR inhibitor, NO scavenger, and NO donor showed that NR-dependent NO level was positively correlated with freezing tolerance. Furthermore, cold acclimation up- and down-regulated expression of P5CS1 and ProDH genes, respectively, resulting in enhanced accumulation of proline (Pro) in wild-type plants. The stimulation of Pro accumulation by cold acclimation was reduced by NR inhibitor and NO scavenger, while Pro accumulation by cold acclimation was not affected by the NOS inhibitor. In contrast to wild-type plants, cold acclimation up-regulated ProDH gene expression in nia1nia2 plants, leading to less accumulation in nia1nia2 plants than in wild-type plants. These findings demonstrate that NR-dependent NO production plays an important role in cold acclimation-induced increase in freezing tolerance by modulating Pro accumulation in Arabidopsis.