Molecular responses of legumes to abiotic stress: Post-translational modifications of proteins and redox signaling

Legumes include several major crops that can fix atmospheric nitrogen in symbiotic root nodules, thus reducing the demand for nitrogen fertilizers and contributing to sustainable agriculture. Global change models predict increases in temperature and extreme weather conditions. This scenario might increase plant exposure to abiotic stresses and negatively affect crop production. Regulation of whole plant physiology and nitrogen fixation in legumes during abiotic stress is complex, and only a few mechanisms have been elucidated. Reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS) are key players in the acclimation and stress tolerance mechanisms of plants. However, the specific redox-dependent signaling pathways are far from understood. One mechanism by which ROS, RNS, and RSS fulfil their signaling role is the post-translational modification (PTM) of proteins. Redox-based PTMs occur in the cysteine thiol group (oxidation, S-nitrosylation, S-glutathionylation, persulfidation), and also in methionine (oxidation), tyrosine (nitration), and lysine and arginine (carbonylation/glycation) residues. Unraveling PTM patterns under different types of stress and establishing the functional implications may give insight into the underlying mechanisms by which the plant and nodule respond to adverse conditions. Here, we review current knowledge on redox-based PTMs and their possible consequences in legume and nodule biology. © 2021 The Author(s) 2021. Published by Oxford University Press on behalf of the Society for Experimental Biology

Function of antioxidant enzymes and metabolites during maturation of pea fruits

Panel (S2-P29) presentado en la Reunión de la Sociedad Española de Fisiología Vegetal (SEFV) (18ª. Zaragoza. 8-11 septiembre 2009).Leguminous plants such as pea (Fisum sativum), bean (Fhaseolus vulgaris) or alfalfa (Medicago sativa) are crops of major economical value as protein source for human and animal consumption. They are also essential to sustainable agricultural systems because of their ability to establish nitrogen-fixing symbioses with soil bacteria, thus providing a biological alternative to chemical fertilization. The concentration of antioxidants in fruits is important agronomically, as it is well documented that antioxidants may protect fruit tissues from potentially toxic reactive oxygen species (ROS) and thus contribute to the stress tolerance of crops. Furthermore, following harvest, fruits have a relatively short shelf-life during which they undergo changes in texture, colour and flavour. Because ROS may be involved in the oxidative processes contributing to fruit deterioration, the antioxidant content is important in terms of both the nutritional value and the post-harvest storage of the fruits. Although the antioxidants are believed to play a crucial role in the ripening process of climacteric fruits, their role in the development, maturation and post-harvest storage of legume fruits is poorly defined. We determined the antioxidant capacity (ascorbate-glutathione pathway, superoxide dismutases, catalases, glutathione peroxidases and peroxiredoxins) of mature fruits from nodulated plants and from plants supplied with combined nitrogen, and concluded that pea fruits from plants dependent on nitrogen fixation show similar antioxidant levels to those dependent on chemical fertilization. Furthermore, oir results showed that fruit maturation causes a decline in the antioxidants of pea fruits. However, the concentration of lipid peroxides and oxidized proteins remained unaltered, suggesting that, contrary to the situation described in climacteric fruits, a decrease in the antioxidant capacity does not necessarily lead to oxidative stress in maturing pea fruits. Similarly, oir data showed that despite the decreases in several antioxidants, oxidative processes are probably not involved in legume fruit deterioration during storage at room temperature. Finally, our results underscore the importance of ascorbate, one of the key components of the antioxidant network, in pea fruit growth and development.This work was funded by Ministerio de Ciencia e Innovación (grant AGL2008-01298) and Gobierno de Aragón (PIP137/2005 and group A53).Peer reviewe

Recent insights into antioxidant defenses of legume root nodules

43 Pag., 2 Tabl., 2 Fig. The definitive version is available at: www3.interscience.wiley.comLegume root nodules are sites of intense biochemical activity and consequently are at high risk of damage as a result of the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). These molecules can potentially give rise to oxidative and nitrosative damage but, when their concentrations are tightly controlled by antioxidant enzymes and metabolites, they also play positive roles as critical components of signal transduction cascades during nodule development and stress. Thus, recent advances in our understanding of ascorbate and (homo)glutathione biosynthesis in plants have opened up the possibility of enhancing N2 fixation through an increase of their concentrations in nodules. It is now evident that antioxidant proteins other than the ascorbate-glutathione enzymes, such as some isoforms of glutathione peroxidases, thioredoxins, peroxiredoxins, and glutathione S-transferases, are also critical for nodule activity. To avoid cellular damage, nodules are endowed with several mechanisms for sequestration of Fenton-active metals (nicotianamine, phytochelatins, and metallothioneins) and for controlling ROS/RNS bioactivity (hemoglobins). The use of ‘omic’ technologies has expanded the list of known antioxidants in plants and nodules that participate in ROS/RNS/antioxidant signaling networks, although aspects of developmental variation and subcellular localization of these networks remain to be elucidated. To this end, a critical point will be to define the transcriptional and post-transcriptional regulation of antioxidant proteins.The research described here was supported by a grant from the National Science Foundation (IOS-0517688) to D.A.D., and a grant from the Spanish Ministry of Science and Innovation-FEDER (AGL2008-01298) and Government of Aragón (group A53) to M.B.Peer reviewe

Sulfur Transport and Metabolism in Legume Root Nodules

Sulfur is an essential nutrient in plants as a constituent element of some amino acids, metal cofactors, coenzymes, and secondary metabolites. Not surprisingly, sulfur deficiency decreases plant growth, photosynthesis, and seed yield in both legumes and non-legumes. In nodulated legumes, sulfur supply is positively linked to symbiotic nitrogen fixation (SNF) and sulfur starvation causes three additional major effects: decrease of nodulation, inhibition of SNF, and slowing down of nodule metabolism. These effects are due, at least in part, to the impairment of nitrogenase biosynthesis and activity, the accumulation of nitrogen-rich amino acids, and the decline in leghemoglobin, ferredoxin, ATP, and glucose in nodules. During the last decade, some major advances have been made about the uptake and metabolism of sulfur in nodules. These include the identification of the sulfate transporter SST1 in the symbiosomal membrane, the finding that glutathione produced in the bacteroids and host cells is essential for nodule activity, and the demonstration that sulfur assimilation in the whole plant is reprogrammed during symbiosis. However, many crucial questions still remain and some examples follow. In the first place, it is of paramount importance to elucidate the mechanism by which sulfur deficiency limits SNF. It is unknown why homoglutahione replaces glutathione as a major water-soluble antioxidant, redox buffer, and sulfur reservoir, among other relevant functions, only in certain legumes and also in different tissues of the same legume species. Much more work is required to identify oxidative post-translational modifications entailing cysteine and methionine residues and to determine how these modifications affect protein function and metabolism in nodules. Likewise, most interactions of antioxidant metabolites and enzymes bearing redox-active sulfur with transcription factors need to be defined. Solving these questions will pave the way to decipher sulfur-dependent mechanisms that regulate SNF, thereby gaining a deep insight into how nodulated legumes adapt to the fluctuating availability of nutrients in the soil

Thiol synthetases of legumes: immunogold localization and differential gene regulation by phytohormones

In plants and other organisms, glutathione (GSH) biosynthesis is catalysed sequentially by γ-glutamylcysteine synthetase (γECS) and glutathione synthetase (GSHS). In legumes, homoglutathione (hGSH) can replace GSH and is synthesized by γECS and a specific homoglutathione synthetase (hGSHS). The subcellular localization of the enzymes was examined by electron microscopy in several legumes and gene expression was analysed in Lotus japonicus plants treated for 1–48 h with 50 μM of hormones. Immunogold localization studies revealed that γECS is confined to chloroplasts and plastids, whereas hGSHS is also in the cytosol. Addition of hormones caused differential expression of thiol synthetases in roots. After 24–48 h, abscisic and salicylic acids downregulated GSHS whereas jasmonic acid upregulated it. Cytokinins and polyamines activated GSHS but not γECS or hGSHS. Jasmonic acid elicited a coordinated response of the three genes and auxin induced both hGSHS expression and activity. Results show that the thiol biosynthetic pathway is compartmentalized in legumes. Moreover, the similar response profiles of the GSH and hGSH contents in roots of non-nodulated and nodulated plants to the various hormonal treatments indicate that thiol homeostasis is independent of the nitrogen source of the plants. The differential regulation of the three mRNA levels, hGSHS activity, and thiol contents by hormones indicates a fine control of thiol biosynthesis at multiple levels and strongly suggests that GSH and hGSH play distinct roles in plant development and stress responses

Análisis comparativo de los métodos de enseñanza tradicional y ludotécnico aplicados al baloncesto en educación física

El objetivo del presente estudio se basa en comparar dos modelos de enseñanza en la E.F. como son el tradicional (basado en el aprendizaje de la técnica de manera directa para que, desde ahí se vaya adquiriendo la táctica por medio de situaciones adaptadas y reales de juego) y el ludotécnico (basado en el aprendizaje de la técnica por medio del de la táctica, cuyo aprendizaje, principalmente, se lleva a cabo por medio de juegos). Para ello, pusimos en práctica dos unidades didácticas (una basada en el modelo tradicional y otra basada en el ludotécnico) en un grupo control y otro experimental y tras concluir estas, llevamos a cabo una situación real de juego en la que grabamos a estos dos grupos para, por medio de la herramienta Game Performance Assessment Instrument, poder llevar a cabo el objetivo del estudio ya mencionado en el párrafo anterior. Tras el análisis hemos podido observar diferencias entre ambos modelos, habiendo una efectividad mayor en la toma de decisiones (táctica) en el modelo ludotécnico y un mejor porcentaje de aciertos en la ejecución de habilidades (técnica) por parte del grupo control en el modelo tradicional

Immunolocalization of antioxidant enzymes in high-pressure frozen root and stem nodules of Sesbania rostrata

34 Pags.- 7 Figs.- 1 Tabl. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1469-8137The activities and localizations of superoxide dismutases (SODs) were compared in root and stem nodules of the semi-aquatic legume Sesbania rostrata using gel-activity assays and immunogold labelling, respectively. Nodules were fixed by high-pressure freezing and dehydrated by freeze substitution. Stem nodules showed more total and specific SOD activities than root nodules because of the presence of chloroplastic CuZnSOD. Most of the total SOD activity of stem and root nodules resulted from 'cytosolic' CuZnSOD, localized in the cytoplasm and chromatin, and from MnSOD in the bacteroids and in the mitochondria of vascular tissue. FeSOD was present in nodule plastids and in leaf chloroplasts, and was found to be associated with chromatin. Superoxide production was detected histochemically in the vascular bundles and in the infected tissue of stem and root nodules, whereas peroxide accumulation was observed in the cortical cell walls and intercellular spaces, as well as within the infection threads of both nodule types. These data suggest a role of CuZnSOD and FeSOD in protecting nuclear DNA from reactive oxygen species and/or in modulating gene activity. The enhanced levels of CuZnSOD, MnSOD and superoxide production in vascular bundle cells are consistent with a role of CuZnSOD and superoxide in the lignification of xylem vessels, but also suggest additional functions in coping with superoxide production by the high respiratory activity of parenchyma cells.This work was supported by the Royal Society (UK), Ministerio de Educación y Ciencia-Fondos Europeos de Desarrollo Regional (AGL2005-01404 and AGL2008-01298) and Gobierno de Aragón (group A53). E.K.J. thanks the Royal Society (UK) and Gobierno de Aragón-Caja Inmaculada (Spain) for funding a sabbatical leave (‘Programa Europa’). M.C.R. was the recipient of a postdoctoral contract (Program I3P) of Consejo Superior de Investigaciones Científicas-Fondo Social Europeo.Peer Reviewe

Glutatión peroxidasas y tiorredoxinas en la leguminosa modelo Lotus japonicus

Las leguminosas constituyen una familia de plantas de gran importancia agronómica y ecológica. En simbiosis con bacterias del suelo, denominadas rizobios, llevan a cabo la fijación biológica de nitrógeno, que genera gran cantidad de especies reactivas de oxígeno y nitrógeno. Para mantenerlas en concentraciones óptimas, las células vegetales contienen metabolitos y enzimas antioxidantes. Entre ellas, las glutation peroxidasas y las tiorredoxinas desempeñan un importante papel en la percepción, integración y transmisión de señales redox y en la protección frente al daño oxidativo en condiciones de estrés. Esta tesis aporta nueva información sobre la función de las glutation peroxidasas y las tiorredoxinas en la simbiosis rizobio-leguminosa