Open Access
Physiological and biochemical characterization of rootlets response to salt stress in two Medicago truncatula Gaertn. ecotypes
(Japanese Society for Root Research, 2018) Amouri, Adel Amar; González García, Esther; Aoul, Seghir Hadjadj; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
Legumes are very important plants both ecologically and agriculturally because they are able to interact symbiotically with rhizobia for biological nitrogen fixation and soil fertilization. Medicago truncatula Gaertn. is an important model legume rich in protein. Salinity represents, today, the major cause of land degradation and crop productivity limitation around the world and affects physiology and metabolism in legumes. In this study, we analyzed the physiological and biochemical responses of rootlets in two contrasting ecotypes of Medicago truncatula (Tru 131, tolerant and Jemalong, sensitive) to different level of NaCl, (68, 102 and 137 mM). Results showed that the tolerant ecotype has a lower water potential than Jemalong. Root protein content of Tru 131 was decreased than Jemalong, this can be explained by accumulation of protein oxidation in the sensitive genotype. Moreover, NaCl increased guaiacol peroxidase activity GPX in rootlets of Tru 131, this enzyme has a protective role against the molecules ROS accumulated during oxidative stress. On the other hand, under salt stress the total content of ascorbate (ASC + DHA) and Glutathione (GSH + GSSG) was increased in the tolerant genotype Tru 131 compared to Jemalong. These results show how the tolerant genotype activate the antioxidative defense system at root level against damages caused by oxidative stress under salinity.
Open Access
Physiological responses of legume nodules to drought
(Global Science Books, 2011) Arrese-Igor Sánchez, César; González García, Esther; Marino Bilbao, Daniel; Ladrera Fernández, Rubén; Larrainzar Rodríguez, Estíbaliz; Gil Quintana, Erena; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
Legumes include important agricultural crops, as their high protein content is of primary importance for human food and animal feed. In addition, the ability of most of them to establish symbiotic relationships with soil bacteria allows them to obtain their N requirements from nitrogen fixation in nodules and, therefore, avoids the use of nitrogen fertilizers. Thus, legumes are also essential to improve the soil fertility and quality of agricultural lands and to reclaim eroded or barren areas, making them crucial for agricultural and environmental sustainability. However, legume nitrogen fixation in crop species is very sensitive to environmental constraints and drought, in particular. The present contribution reviews our current knowledge on the processes involved in this inhibition, with particular emphasis on oxygen, nitrogen and carbon physiology. Emerging aspects such as oxidative damage, C/N interactions and sulphur metabolism together with future prospects are also discussed.
Open Access
Proyecto río Arga: ciencia ciudadana, biodiversidad & educación
(2022) González García, Esther; Peralta de Andrés, Francisco Javier; Ciencias; Zientziak; Gobierno de Navarra / Nafarroako Gobernua, CENEDUCA3-2019
El objetivo del proyecto ARGA, desarrollado en la plataforma iNaturalist (https://www.inaturalist.org/projects/arga), es reunir observaciones de las especies presentes en el río Arga a su paso por la Cuenca de Pamplona. Cualquier persona puede participar, aunque en su creación se ha pensado en su utilización principalmente por estudiantes de Enseñanza Secundaria. Este proyecto se lleva a cabo en colaboración con la Mancomunidad de la Comarca de Pamplona a través del programa Mancoeduca, que ofrece actividades de educación ambiental dirigidas a centros de educación secundaria en el entorno del río Arga.
Open Access
Is N-feedback involved in the inhibition of nitrogen fixation in drought-stressed Medicago truncatula?
(Oxford University Press, 2013) Gil Quintana, Erena; Larrainzar Rodríguez, Estíbaliz; Arrese-Igor Sánchez, César; González García, Esther; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa: 735/2008
Drought stress is a major factor limiting nitrogen fixation (NF) in crop production. However, the regulatory mechanism involved and the origin of the inhibition, whether local or systemic, is still controversial and so far scarcely studied in temperate forage legumes. Medicago truncatula plants were symbiotically grown with a split-root system and exposed to gradual water deprivation. Physiological parameters, NF activity, and amino acid content were measured. The partial drought treatment inhibited NF in the nodules directly exposed to drought stress. Concomitantly, in the droughted below-ground organs, amino acids accumulated prior to any drop in evapotranspiration (ET). It is concluded that drought exerts a local inhibition of NF and drives an overall accumulation of amino acids in diverse plant organs which is independent of the decrease in ET. The general increase in the majority of single amino acids in the whole plant questions the commonly accepted concept of a single amino acid acting as an N-feedback signal.
Open Access
Use of recombinant iron-superoxide dismutase as a marker of nitrative stress
(Elservier, 2008-04-20) Larrainzar Rodríguez, Estíbaliz; Urarte Rodríguez, Estíbaliz; Auzmendi, Iñigo; Ariz Arnedo, Idoia; Arrese-Igor Sánchez, César; González García, Esther; Morán Juez, José Fernando; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua; Gobierno de Navarra / Nafarroako Gobernua, 57/2007
Superoxide dismutases (SODs; EC 1.15.1.1) are a group of metalloenzymes which are essential to protect cells under aerobic conditions. In biological systems, it has been reported that SODs and other proteins are susceptible to be attacked by peroxynitrite (ONOO-) which can be originated from the reaction of nitric oxide with superoxide radical. ONOO- is a strong oxidant molecule capable of nitrating peptides and proteins at the phenyl side chain of the tyrosine residues. In the present work, bovine serum albumin (BSA) and recombinant iron¿superoxide dismutase from the plant cowpea (Vu_FeSOD) are used as target molecules to estimate ONOO- production. The method employs the compound SIN-1, which simultaneously generates -NO and O2- in aerobic aqueous solutions. First, assay conditions were optimized incubating BSA with different concentrations of SIN-1, and at a later stage, the effect on the tyrosine nitration and catalytic activity of Vu_FeSOD was examined by in-gel activity and spectrophotometric assays. Both BSA and Vu_FeSOD are nitrated in a dose-dependent manner, and, at least in BSA nitration, the reaction seems to be metal catalyzed.
Open Access
Unlocking nature's drought resilience: a focus on the parsimonious root phenotype and specialised root metabolism in wild Medicago populations
(Springer Nature, 2024-10-28) Calleja Satrustegui, Aitziber; Echeverría Obanos, Andrés; Ariz Arnedo, Idoia; Peralta de Andrés, Francisco Javier; González García, Esther; Ciencias; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB; Unviersidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Background and aims: crop wild relatives, exposed to strong natural selection, exhibit effective tolerance traits against stresses. While an aggressive root proliferation phenotype has long been considered advantageous for a range of stresses, it appears to be counterproductive under drought due to its high metabolic cost. Recently, a parsimonious root phenotype, metabolically more efficient, has been suggested to be better adapted to semiarid environments, although it is not clear that this phenotype is a trait exhibited by crop wild relatives. Methods: firstly, we analysed the root phenotype and carbon metabolism in four Medicago crop wild relatives adapted to a semiarid environment and compared them with the cultivated M. truncatula Jemalong (A17). Secondly, we exposed the cultivated (probably the least adapted genotype to aridity) and the wild (the most common one in arid zones) M. truncatula genotypes to water deficit. The carbon metabolism response in different parts of their roots was analysed. Results: a reduced carbon investment per unit of root length was a common trait in the four wild genotypes, indicative of an evolution towards a parsimonious root phenotype. During the water deficit experiment, the wild M. truncatula showed higher tolerance to drought, along with a superior ability of its taproot to partition sucrose and enhanced capacity of its fibrous roots to maintain sugar homeostasis. Conclusion: a parsimonious root phenotype and the spatial specialization of root carbon metabolism represent two important drought tolerance traits. This work provides relevant findings to understand the response of Medicago species roots to water deficit.
Open Access
Split‐root systems applied to the study of the legume‐rhizobial symbiosis: what have we learned?
(Wiley, 2014) Larrainzar Rodríguez, Estíbaliz; Gil Quintana, Erena; Arrese-Igor Sánchez, César; González García, Esther; Marino Bilbao, Daniel; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
Split-root system (SRS) approaches allow the differential treatment of separate and independent root systems, while sharing a common aerial part. As such, SRS is a useful tool for the discrimination of systemic (shoot origin) versus local (root/nodule origin) regulation mechanisms. This type of approach is particularly useful when studying the complex regulatory mechanisms governing the symbiosis established between legumes and Rhizobium bacteria. The current work provides an overview of the main insights gained from the application of SRS approaches to understand how nodule number (nodulation autoregulation) and nitrogen fixation are controlled both under non-stressful conditions and in response to a variety of stresses. Nodule number appears to be mainly controlled at the systemic level through a signal which is produced by nodule/root tissue, translocated to the shoot, and transmitted back to the root system, involving shoot Leu-rich repeat receptor-like kinases. In contrast, both local and systemic mechanisms have been shown to operate for the regulation of nitrogenase activity in nodules. Under drought and heavy metal stress, the regulation is mostly local, whereas the application of exogenous nitrogen seems to exert a regulation of nitrogen fixation both at the local and systemic levels.
Open Access
Drought stress causes a reduction in the biosynthesis of ascorbic acid in soybean plants
(Frontiers Media, 2017) Seminario Huárriz, Amaia; Song, Li; Zulet González, Amaia; Nguyen, Henry T.; González García, Esther; Larrainzar Rodríguez, Estíbaliz; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Gobierno de Navarra / Nafarroako Gobernua, 2016/PI013; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, 1287/2011
Drought provokes a number of physiological changes in plants including oxidative damage. Ascorbic acid (AsA), also known as vitamin C, is one of the most abundant water-soluble antioxidant compound present in plant tissues. However, little is known on the regulation of AsA biosynthesis under drought stress conditions. In the current work we analyze the effects of water deficit on the biosynthesis of AsA by measuring its content, in vivo biosynthesis and the expression level of genes in the Smirnoff-Wheeler pathway in one of the major legume crop, soybean (Glycine max L. Merr). Since the pathway has not been described in legumes, we first searched for the putative orthologous genes in the soybean genome. We observed a significant genetic redundancy, with multiple genes encoding each step in the pathway. Based on RNA-seq analysis, expression of the complete pathway was detected not only in leaves but also in root tissue. Putative paralogous genes presented differential expression patterns in response to drought, suggesting the existence of functional specialization mechanisms. We found a correlation between the levels of AsA and GalLDH biosynthetic rates in leaves of drought-stressed soybean plants. However, the levels of GalLDH transcripts did not show significant differences under water deficit conditions. Among the other known regulators of the pathway, only the expression of VTC1 genes correlated with the observed decline in AsA in leaves.
Open Access
Insights into the regulation of nitrogen fixation in pea nodules: lessons from drought, abscisic acid and increased photoassimilate availability
(EDP Sciences, 2001) González García, Esther; Gálvez, Loli; Royuela Hernando, Mercedes; Aparicio Tejo, Pedro María; Arrese-Igor Sánchez, César; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
Nitrogen fixation in legume nodules has been shown to be very sensitive to drought and other environmental constraints. It has been widely assumed that this decline in nitrogen fixation was a consequence of an increase in the so-called oxygen diffusion barrier and a subsequent impairment to bacteroid respiration. However, it has been recently shown that nitrogen fixation is highly correlated with nodule sucrose synthase (SS) activity under drought and other environmental stresses. Whether this correlation reflects a causative relationship or not has not been proven yet. The evidence presented here suggests that SS controls nitrogen fixation under mild drought conditions. However, nitrogen fixation cannot be enhanced only by increasing glycolytic flux, as under these conditions nodules become oxygen limited. Abscisic acid also induces a decline in nitrogen fixation that is independent of SS. The overall results suggest the occurrence of a complex regulation of nodule nitrogen fixation involving, at least, both carbohydrate and oxygen fluxes within the nodule.
Open Access
Local inhibition of nitrogen fixation and nodule metabolism in drought-stressed soybean
(Oxford University Press, 2013) Gil Quintana, Erena; Larrainzar Rodríguez, Estíbaliz; Seminario Huárriz, Amaia; Díaz Leal, Juan Luis; Alamillo, Josefa M.; Pineda, Manuel; Arrese-Igor Sánchez, César; Wienkoop, Stefanie; González García, Esther; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa: 735/2008; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa: 134/2012
Drought stress is a major factor limiting symbiotic nitrogen fixation (NF) in soybean crop production. However, the regulatory mechanisms involved in this inhibition are still controversial. Soybean plants were symbiotically grown in a split-root system (SRS), which allowed for half of the root system to be irrigated at field capacity while the other half remained water deprived. NF declined in the water-deprived root system while nitrogenase activity was maintained at control values in the well-watered half. Concomitantly, amino acids and ureides accumulated in the water-deprived belowground organs regardless of transpiration rates. Ureide accumulation was found to be related to the decline in their degradation activities rather than increased biosynthesis. Finally, proteomic analysis suggests that plant carbon metabolism, protein synthesis, amino acid metabolism, and cell growth are among the processes most altered in soybean nodules under drought stress. Results presented here support the hypothesis of a local regulation of NF taking place in soybean and downplay the role of ureides in the inhibition of NF