Open Access
Legume nitrogen utilization under drought stress
(Springer, 2018) Castañeda Presa, Verónica; Gil Quintana, Erena; Echeverría Obanos, Andrés; González García, Esther; Ciencias; Zientziak
Legumes account for around 27% of the world’s primary crop production and can be classified based on their use and traits into grain and forage legumes. Legumes can establish symbiosis with N-fixing soil bacteria. As a result, a new organ is formed, the nodule, where the reduction of atmospheric N2 into ammonia is carried out catalyzed by the bacterial exclusive enzyme nitrogenase. The process, highly energy demanding, is known as symbiotic nitrogen fixation and provides all the N needs of the plant, thus avoiding the use of N fertilizers in the context of sustainable agriculture. However, legume crops are often grown under non-fixing conditions since legume nodulation is suppressed by high levels of soil nitrogen occurring in chemically fertilized agro-environment. In addition, legumes are very sensitive to environmental stresses, being drought one of the significant constraints affecting crop production. Due to their agricultural and economic importance, scientists have carried out basic and applied research on legumes to better understand responses to abiotic stresses and to further comprehend plant–microbe interactions. An integrated view of nitrogen utilization under drought stress will be presented with particular focus on legume crops.
Open Access
Functional analysis of the taproot and fibrous roots of Medicago truncatula: sucrose and proline catabolism primary response to water deficit
(Elsevier, 2019) Castañeda Presa, Verónica; Peña, Marlon de la; Azcárate Górriz, Lidia; Aranjuelo Michelena, Iker; González García, Esther; Ciencias; Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Root performance represents a target factor conditioning plant development under drought conditions. Moreover, recent root phenotyping studies remark relevant differences on functionality of the different root types. However, despite its relevance, the performance of different types of roots such as primary/taproot (tapR) and lateral/fibrous roots (fibR) under water stress conditions is largely unknown. In the current study, the impact of water stress on target C and N metabolism (namely sucrose and proline) processes were characterized in tapR and fibR of Medicago truncatula plants exposed to different water stress severity regimes (moderate versus severe). While both root types exhibit some common responses to face water stress, the study highlighted important physiological and metabolic differences between them. The tapR proved to have an essential role on carbon and nitrogen partitioning rather than just on storage. Moreover, this root type showed a higher resilience towards water deficit stress. Sucrose metabolization at sucrose synthase level was early blocked in this tissue together with a selective accumulation of some amino acids such as proline and branched chain amino adds, which may act as alternative carbon sources under water deficit stress conditions. The decline in respiration, despite the over-accumulation of carbon compounds, suggests a modulation at sucrose cleavage level by sucrose synthase and invertase. These data not only provide new information on the carbon and nitrogen metabolism modulation upon water deficit stress but also on the different role, physiology, and metabolism of the taproot and fibrous roots. In addition, obtained results highlight the fact that both root types show distinct performance under water deficit stress; this factor can be of great relevance to improve breeding programs for increasing root efficiency under adverse conditions.
Open Access
A proteomic approach reveals new actors of nodule response to drought in split-root grown pea plants
(Wiley, 2014) Irar, Sami; González García, Esther; Arrese-Igor Sánchez, César; Marino Bilbao, Daniel; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
Drought is considered the more harmful abiotic stress resulting in crops yield loss. Legumes in symbiosis with rhizobia are able to fix atmospheric nitrogen. Biological nitrogen fixation (SNF) is a very sensitive process to drought and limits legumes agricultural productivity. Several factors are known to regulate SNF including oxygen availability to bacteroids, carbon and nitrogen metabolisms; but the signalling pathways leading to SNF inhibition are largely unknown. In this work, we have performed a proteomic approach of pea plants grown in split-root-system where one half of the root was well-irrigated and the other was subjected to drought. Water stress locally provoked nodule water potential decrease that led to SNF local inhibition. The proteomic approach revealed 11 and 7 nodule proteins regulated by drought encoded by P. sativum and R. leguminosarum genomes respectively. Among these 18 proteins, three proteins related to flavonoid metabolism, two to sulphur metabolism and three RNA-binding proteins were identified. These proteins could be molecular targets for future studies focused on the improvement of legumes tolerance to drought. Moreover, this work also provides new hints for the deciphering of SNF regulation machinery in nodules.
Open Access
iNaturalist Arga: acercándonos a la biodiversidad de los ríos urbanos para aprender a cuidarlos
(Fundación Conama, 2021) González García, Esther; Peralta de Andrés, Francisco Javier; García, Mar; Alzueta, José; Fernández Escalada, Manuel; Marzo Pérez, Asier; Aliende, Andrea; Miguel, Jon; Alvira Guallart, María Aránzazu; Ciencias; Zientziak; Gobierno de Navarra / Nafarroako Gobernua, CENEDUCA3-2019
La biodiversidad es un concepto que forma parte del currículo de la educación secundaria. Las herramientas TIC (Tecnologías de la Información y la Comunicación) colaborativas abiertas disponibles ofrecen nuevas posibilidades para el ampliar el conocimiento sobre biodiversidad de los estudiantes de secundaria y futuros ciudadanos. Este estudio utiliza la plataforma de ciencia ciudadana iNaturalist como herramienta de utilidad en el currículo sobre biodiversidad incluido en la educación secundaria obligatoria. En este contexto, se ha creado un proyecto en esta plataforma centrado en el río Arga que atraviesa la ciudad de Pamplona: https://www.inaturalist.org/projects/arga. El proyecto implica a centros de educación secundaria, formación profesional y educación ambiental para realizar observaciones sobre biodiversidad en el entorno dicho río. Su objetivo es mejorar el conocimiento de los estudiantes de educación secundaria del concepto biodiversidad así como del río, además de poner en valor este ecosistema fluvial en un entorno urbano en las futuras generaciones. El proyecto fue puesto en marcha en el curso 2019-2020 e incorpora 468 observaciones de 213 especies aportadas por 39 observadores y 140 identificadores han colaborado en su validación. Aunque la participación en ese curso fue limitada a un centro educativo como consecuencia de la pandemia COVID, esta experiencia ha servido como modelo para el futuro desarrollo del proyecto. En el curso 2020-2021 se vuelve a poner en marcha el proyecto ARGA con el objetivo de establecerse como una herramienta de referencia para la comunidad educativa y de conectar el sector educativo con la sociedad en torno al concepto biodiversidad para destacar su importancia en la calidad ambiental en medios urbanos.
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
Strategies to aply water-deficit stress: similarities and disparities at the whole plant metabolism level in medicago truncatula
(MDPI, 2021) Castañeda Presa, Verónica; González García, Esther; Ciencias; Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Water-deficit stresses such as drought and salinity are the most important factors limiting crop productivity. Hence, understanding the plant responses to these stresses is key for the improvement of their tolerance and yield. In this study M. truncatula plants were subjected to 250 mM NaCl as well as reduced irrigation (No-W) and 250 g/L polyethylene glycol (PEG)-6000 to induce salinity and drought stress, respectively, provoking a drop to −1.7 MPa in leaf water potential. The whole plant physiology and metabolism was explored by characterizing the stress responses at root, phloem sap and leaf organ level. PEG treatment led to some typical responses of plants to drought stress, but in addition to PEG uptake, an important impairment of nutrient uptake and a different regulation of carbon metabolism could be observed compared to No-W plants. No-W plants showed an important redistribution of antioxidants and assimilates to the root tissue, with a distinctive increase in root proline degradation and alkaline invertase activity. On the contrary, salinity provoked an increase in leaf starch and isocitrate dehydrogenase activity, suggesting key roles in the plant response to this stress. Overall, results suggest higher protection of salt-stressed shoots and non-irrigated roots through different mechanisms, including the regulation of proline and carbon metabolism, while discarding PEG as safe mimicker of drought. This raises the need to understand the effect at the whole plant level of the different strategies employed to apply water-deficit stress.
Open Access
Learning plant biodiversity in nature: the use of the citizen–science platform iNaturalist as a collaborative tool in secondary education
(MDPI, 2021) Echeverría Obanos, Andrés; Ariz Arnedo, Idoia; Moreno Echeverría, Judit; Peralta de Andrés, Francisco Javier; González García, Esther; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB; Ciencias; Gobierno de Navarra / Nafarroako Gobernua, CENEDUCA3/2019
Biodiversity is a concept of great scientific interest and social value studied in different subjects of the secondary education curriculum. Citizen–science programs may contribute to increasing the engagement of students when studying biodiversity. This work aimed to explore the use of the citizen–science platform iNaturalist as a complement of the elaboration of herbaria in an outdoor activity for 4th course 16-year-old students in the Basaula Reserve. The platform iNaturalist was chosen for its suitability to develop collaborative projects in an educational context. The Basaula project was created and 122 students were trained to record plant species in an outdoor activity. A total of 32 species were recorded, among them the most abundant were beech (Fagus sylvatica) and holm oak (Quercus ilex). The students positively evaluated their experience, highlighting its adequacy to record biodiversity data and make a virtual herbarium. Students valued the innovative character of iNaturalist and its usefulness for research but also the opportunity to integrate mobile devices in school education. We concluded that iNaturalist is a valuable tool to carry out collaborative projects dealing with biodiversity in secondary education.
Open Access
Root system of Medicago sativa and Medicago truncatula: drought effects on carbon metabolism
(Springer, 2021-03-18) Echeverría Obanos, Andrés; González García, Esther; Ciencias; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB
Aims: Here, we assess the differential impact of drought on root carbon metabolism in the widely cultivated alfalfa (Medicago sativa, Ms) and the model legume Medicago truncatula (Mt). Understanding how carbon allocation is regulated under drought stress conditions is a central issue to improving alfalfa productivity under future climate change scenarios. Methods: Alfalfa and Medicago truncatula were compared under water deficit conditions. Root carbon metabolism of the taproot and fibrous roots was analysed. M. truncatula drought tolerance variability was compared to that of alfalfa using six accessions of the Medicago Hapmap project. The prominent taproot is much less developed in M. truncatula than in alfalfa with the former exhibiting an extensive fibrous root system. Results: In both examined Medicago species the taproot contained the major pools of soluble protein, sucrose and pinitol, whereas the major pools of hexoses and carbon metabolism enzymes appeared to be in the fibrous roots. Under water-deficit conditions, the response of M. sativa strongly differed from that of M. truncatula at the root level. Conclusions: Water deficit conditions differentially modulate the root carbon metabolism of M. sativa and M. truncatula. Mt maintained a more active carbon metabolism in the fibRs, as sucrose, myo-inositol and pinitol accumulated to cope with the water deficit (WD). Conversely, the root system of Ms did not accumulate cyclitols and carbon metabolism was more severely affected under water deficit conditions. This differentially exerted control may determine the drought response of these two close relatives.
Open Access
Long-term mannitol-induced osmotic stress leads to stomatal closure, carbohydrate accumulation and changes in leaf elasticity in Phaselous vulgaris leaves
(Academic Journals, 2010) Sassi, Sameh; Aydi, Samir; Hessini, Kamel; González García, Esther; Arrese-Igor Sánchez, César; Abdelly, Chedly; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
The effect of long-term osmotic stress was investigated in leaves of two common bean lines, with contrasting tolerance: Flamingo (tolerant) and coco blanc (sensitive). Water relations, organic solute, ion accumulation and amino acids content as well as osmotic adjustment (OA) were studied during an extended exposure to osmotic stress. Osmotic stress was applied by means of 50 mM mannitol for 15 days. At the end of the stress period, both osmotic potential at full turgor (psi(100)) and at turgor loss point (psi(0)) decreased significantly in stressed plants compared with the control. The decrease being greater in the sensitive line, showed a greater OA compared with flamingo. Sugars contents increased in stressed plants and seem to be the major components of osmotic adjustment in stressed common bean leaves. The increase was more marked in coco blanc. Osmotic stress tolerance could thus not be associated with higher OA. The possible role of decreased leaf cell elasticity (epsilon(max)) is discussed in relation to osmotic stress tolerance in this species.
Open Access
Drought stress provokes the down-regulation of methionine and ethylene biosynthesis pathways in Medicago truncatula roots and nodules
(Wiley, 2014) Larrainzar Rodríguez, Estíbaliz; Molenaar, Johanna A.; Wienkoop, Stefanie; Gil Quintana, Erena; Alibert, Bénédicte; Limami, Anis M.; Arrese-Igor Sánchez, César; González García, Esther; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, 735/2008
Symbiotic nitrogen fixation is one of the first physiological processes inhibited in legume plants under water-deficit conditions. Despite the progress made in the last decades, the molecular mechanisms behind this regulation are not fully understood yet. Recent proteomic work carried out in the model legume Medicago truncatula provided the first indications of a possible involvement of nodule methionine (Met) biosynthesis and related pathways in response to waterdeficit conditions. To better understand this involvement, the drought-induced changes in expression and content of enzymes involved in the biosynthesis of Met, S-adenosyl-Lmethionine (SAM) and ethylene in M. truncatula root and nodules were analyzed using targeted approaches. Nitrogenfixing plants were subjected to a progressive water deficit and a subsequent recovery period. Besides the physiological characterization of the plants,the content of total sulphur,sulphate and main S-containing metabolites was measured. Results presented here show that S availability is not a limiting factor in the drought-induced decline of nitrogen fixation rates in M. truncatula plants and provide evidences for a downregulation of the Met and ethylene biosynthesis pathways in roots and nodules in response to water-deficit conditions.