Open Access
Nitrogen fertilization form and energetic status as target points conditioning rice responsiveness to elevated [CO2]
(Frontiers Media, 2025-03-11) Jáuregui Mosquera, Iván; Mitsui, Toshiaki; Gakière, Bertrand; Mauve, Caroline; Gilard, Françoise; Aranjuelo Michelena, Iker; Baslam, Marouane; Ciencias; Zientziak
The nitrogen (N) fertilization form and plant energy status are known to significantly influence plant responses to elevated atmospheric carbon dioxide (CO2) concentrations. However, a close examination of the interplay between N sources under contrasting light intensity has been notably absent in the literature. In this study, we conducted a factorial experiment with rice plants involving two different light intensities (150 and 300 µmol m-2 s-1), inorganic N sources [nitrate (N-NO3) or ammonium nitrate (N-NH4NO3)] at varying CO2 levels (410 and 700 parts per million, ppm). The aim was to examine the individual and combined effects of these factors on the allocation of biomass in whole plants, as well as on leaf-level photosynthetic characteristics, chloroplast morphology and development, ATP content, ionomics, metabolomics, and hormone profiles. Our research hypothesis posits that mixed nutrition enhances plant responsiveness to elevated CO2 (eCO2) at both light levels compared to sole N-NO3 nutrition, due to its diminished energy demands for plant assimilation. Our findings indicate that N-NO3 nutrition does not promote the growth of rice, its photosynthetic capacity, or N content when exposed to ambient CO2 (aCO2), and is significantly reduced in low light (LL) conditions. Rice plants with N-NH4NO3 exhibited a higher carboxylation capacity, which resulted in larger biomass (total C, tiller number, and lower root-shoot ratio) supported by higher Calvin-cycle-related sugars. The lower leaf N content and overall amino acid levels at eCO2, particularly pronounced in N-NO3, combined with the lower ATP content (lowest at LL and N-NO3), may reflect the higher energy costs of N assimilation at eCO2. We also observed significant plasticity patterns in leaves under eCO2. Our findings highlight the importance of a thorough physiological understanding to inform innovative management practices aimed at mitigating the negative effects of climate change on plant N use efficiency.
Open Access
Nitrogen source as key factor conditioning responsiveness of Arabidopsis plants to elevated CO2 conditions
(2014) Jáuregui Mosquera, Iván; Aparicio Tejo, Pedro María; Aranjuelo Michelena, Iker; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
The amount of carbon dioxide (CO2) in Earth's atmosphere has exceeded 400 parts per million (ppm) during three continuous months of observations in 2014, which is an absolute record for the last 800,000 years. As a consequence, plants, as photosynthetic organisms, will inevitably be influenced by the changed growing conditions that result from the increased [CO2]. The effect of increased [CO2] on plants has been widely studied and goes far beyond favouring carboxylation of Rubisco and generating higher growth rates. The present thesis aims to highlight the relevance of different nitrogen sources in the response of Arabidopsis thaliana, a C3 model plant, to elevated [CO2]. For this purpose, this has been an integrated study of leaf and root organs combining techniques that range from plant physiology to molecular biology. Under nitrate nutrition and elevated [CO2] conditions, Arabidopsis thaliana plants increase their biomass and maximum photosynthetic rates; nevertheless, the total soluble protein, Rubisco content and leaf N content reveal a general decrease in leaf N availability (chapter I). Although the expression of nitrate transporters was substantially upregulated in roots, plants did not efficiently transport nitrate and other minerals from roots to leaves, which compromised leaf N and mineral status. Therefore, our results suggest that the diminution of transpiration rates causes a reduction in the xylem flux, which inexorably generates an imbalance in the transport of nitrate and mineral elements between organs under elevated [CO2]. Moreover, root nitrate assimilation (based on the amino acid content) is favoured in order to overcome N limitations due to the reduction in leaf nitrate assimilation. In chapter II plant performance under elevated [CO2] and ammonium nitrate conditions was characterized and it was found that biomass doubled due to substantially increased photosynthetic rates. Gas exchange characterization revealed that these plants overcame photosynthetic acclimation. Plants maintained Rubisco concentrations at control levels alongside enhanced energy efficiency. The increments found in leaf carbohydrates and organic acid content linked to enhanced respiration rates supported the fact that the plants under elevated [CO2] maintained their energy status. The transcriptomic analysis enabled the identification of photoassimilate allocation and remobilization as fundamental processes used by the plants to avoid photosynthetic acclimatization. Moreover, based on the relationship between plant carbon status and hormone functioning, the transcriptomic analyses provided an explanation of why phenology accelerates under elevated [CO2]. Finally, in chapter III the relevance of ammonium nutrition under elevated [CO2] was analysed; for this purpose a double nitrate reductase mutant (NR mutant, nia1-1/chl3-5 defective) was used. These results highlight that plants under elevated [CO2] which preferentially assimilate ammonium as their only N source maintain leaf growth and photosynthetic rates similar to plants receiving ammonium nitrate. However, under ambient [CO2] concentrations, ammonium toxicity symptoms emerge and development is extremely constrained. In elevated [CO2] conditions, an NR mutant maintained the energy supply for the Calvin cycle pathway and managed efficient photoassimilate transport between plant tissues. Furthermore, the data suggest active ammonium assimilation in leaves due to the exceptional conditions (C skeletons, ATP, adequate pH homeostasis and no photoinhibition) of these plants under elevated [CO2]. Hence, the results obtained in the present doctoral thesis aim towards the incorporation of the source of nitrogen as key in the response at the elevated [CO2] of Arabidopsis thaliana plants. Consequently, the present doctoral thesis aims to determine whether the incorporation of the correct source of nitrogen is the key component in how Arabidopsis thaliana plants respond to elevated [CO2].
Open Access
Overexpression of a pine Dof transcription factor in hybrid poplars: A comparative study in trees growing under controlled and natural conditions
(Public Library of Science, 2017) Rueda López, Marina; Pascual, María Belén; Pallero, Mercedes; Henao, Luisa María; Lasa Larrea, Berta; Jáuregui Mosquera, Iván; Aparicio Tejo, Pedro María; Cánovas, Francisco M.; Ávila, Concepción; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
In this work, the role of the pine transcriptional regulator Dof 5 in carbon and nitrogen metabolism has been examined in poplar trees. The overexpression of the gene and potential effects on growth and biomass production were compared between trees growing in a growth chamber under controlled conditions and trees growing in a field trial during two growth seasons. Ten-week-old transgenic poplars exhibited higher growth than untransformed controls and exhibited enhanced capacity for inorganic nitrogen uptake in the form of nitrate. Furthermore, the transgenic trees accumulated significantly more carbohydrates such as glucose, fructose, sucrose and starch. Lignin content increased in the basal part of the stem likely due to the thicker stem of the transformed plants. The enhanced levels of lignin were correlated with higher expression of the PAL1 and GS1.3 genes, which encode key enzymes involved in the phenylalanine deamination required for lignin biosynthesis. However, the results in the field trial experiment diverged from those observed in the chamber system. The lines overexpressing PpDof5 showed attenuated growth during the two growing seasons and no modification of carbon or nitrogen metabolism. These results were not associated with a decrease in the expression of the transgene, but they can be ascribed to the nitrogen available in the field soil compared to that available for growth under controlled conditions. This work highlights the paramount importance of testing transgenic lines in field trials.
Open Access
Elevated CO2 improved the growth of a double nitrate reductase defective mutant of Arabidopsis thaliana: the importance of maintaining a high energy status
(Elsevier, 2017) Jáuregui Mosquera, Iván; Aparicio Tejo, Pedro María; Baroja Fernández, Edurne; Ávila, Concepción; Aranjuelo Michelena, Iker; Natura Ingurunearen Zientziak; Ciencias del Medio Natural; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
Impairments in leaf nitrogen (N) assimilation in C3 plants have been identified as processes conditioning photosynthesis under elevated [CO2], especially when N is supplied as nitrate. Leaf N status is usually improved under ammonium nutrition and elevated [CO2]. However, ammonium fertilization is usually accompanied by the appearance of oxidative stress symptoms, which constrains plant development. To understand how the limitations of direct fertilization with ammonium (growth reduction attributed to ammonium toxicity) can be overcome, the effects of elevated [CO2] (800 ppm) exposure were studied in the Arabidopsis thaliana double nitrate reductase defective mutant, nia1-1/chl3-5 (which preferentially assimilates ammonium as its nitrogen source). Analysis of the physiology, metabolites and gene expression was carried out in roots and shoot organs. Our study clearly showed that elevated [CO2] improved the inhibited phenotype of the nitrate reductase double mutant. Both the photosynthetic rates and the leaf N content of the NR mutant under elevated CO2 were similar to wild type plants. The growth of the nitrate reductase mutant was linked to its ability to overcome ammonium-associated photoinhibition processes at 800 ppm [CO2]. More specifically: (i) the capacity of NR mutants to equilibrate energy availability, as reflected by the electron transport equilibrium reached (photosynthesis, photorespiration and respiration), (ii) as well as by the upregulation of genes involved in stress tolerance were identified as the processes involved in the improved performance of NR mutants.
Open Access
The physiological implications of urease inhibitors on N metabolism during germination of Pisum sativum and Spinacea oleracea seeds
(Elsevier, 2012-03-08) Ariz Arnedo, Idoia; Cruchaga Moso, Saioa; Lasa Larrea, Berta; Morán Juez, José Fernando; Jáuregui Mosquera, Iván; Aparicio Tejo, Pedro María; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
The development of new nitrogen fertilizers is necessary to optimize crop production whilst improving the environmental aspects arising from the use of nitrogenous fertilization as a cultural practice. The use of urease inhibitors aims to improve the efficiency of urea as a nitrogen fertilizer by preventing its loss from the soil as ammonia. However, although the action of urease inhibitors is aimed at the urease activity in soil, their availability for the plant may affect its urease activity. The aim of this work was therefore to evaluate the effect of two urease inhibitors, namely acetohydroxamic acid (AHA) and N-(n-butyl) thiophosphoric triamide (NBPT), on the germination of pea and spinach seeds. The results obtained show that urease inhibitors do not affect the germination process to any significant degree, with the only process affected being imbibition in spinach, thus also suggesting different urease activities for both plants. Our findings therefore suggest an activity other than the previously reported urolytic activity for urease in spinach. Furthermore, of the two inhibitors tested, NBPT was found to be the most effective at inhibiting urease activity, especially in pea seedlings.
Open Access
Does the response of Rubisco and photosynthesis to elevated [CO2] change with unfavourable environmental conditions?
(Oxford University Press, 2024-09-12) Ancín Rípodas, María; Gámez Guzmán, Angie Lorena; Jáuregui Mosquera, Iván; Galmes, J.; Sharwood, R. E.; Erice, G.; Ainsworth, E. A.; Tissue, D. T.; Sanz-Sáez, A.; Aranjuelo Michelena, Iker; Ciencias; Zientziak; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura
Climate change due to anthropogenic CO2 emissions affects plant performance globally. To improve crop resilience, we need to understand the effects of elevated CO2 concentration (e[CO2]) on CO2 assimilation and Rubisco biochemistry. However, the interactive effects of e[CO2] and abiotic stress are especially unclear. This study examined the CO2 effect on photosynthetic capacity under different water availability and temperature conditions in 42 different crop species, varying in functional group, photosynthetic pathway, and phenological stage. We analysed close to 3000 data points extracted from 120 published papers. For C-3 species, e[CO2] increased net photosynthesis and intercellular [CO2], while reducing stomatal conductance and transpiration. Maximum carboxylation rate and Rubisco in vitro extractable maximal activity and content also decreased with e[CO2] in C-3 species, while C-4 crops are less responsive to e[CO2]. The interaction with drought and/or heat stress did not significantly alter these photosynthetic responses, indicating that the photosynthetic capacity of stressed plants responded to e[CO2]. Moreover, e[CO2] had a strong effect on the photosynthetic capacity of grasses mainly in the final stages of development. This study provides insight into the intricate interactions within the plant photosynthetic apparatus under the influence of climate change, enhancing the understanding of mechanisms governing plant responses to environmental parameters.
Open Access
Unraveling the role of transient starch in the response of Arabidopsis to elevated CO2 under long-day conditions
(Elsevier, 2018) Jáuregui Mosquera, Iván; Pozueta Romero, Javier; Aparicio Tejo, Pedro María; Baroja Fernández, Edurne; Aranjuelo Michelena, Iker; Zientziak; Ciencias; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
Previous studies on Arabidopsis under long-term exposure to elevated CO2 have been conducted using starch synthesis and breakdown mutants cultured under short day conditions. These studies showed that starch synthesis can ameliorate the photosynthetic reduction caused by soluble sugar-mediated feedback regulation. In this work we characterized the effect of long-term exposure to elevated CO2 (800 ppm) on growth, photosynthesis and content of primary photosynthates in long-day grown wild type plants as well as the near starch-less (aps1) and the starch-excess (gwd) mutants. Notably, elevated CO2 promoted growth of both wild type and aps1 plants but had no effect on gwd plants. Growth promotion by elevated CO2 was accompanied by an increased net photosynthesis in WT and aps1 plants. However, the plants with the highest starch content (wild type at elevated CO2, gwd at ambient CO2, and gwd at elevated CO2) were the ones that suffered decreased in in vivo maximum carboxylation rate of Rubisco, and therefore, photosynthetic down-regulation. Further, the photosynthetic rates of wild type at elevated CO2 and gwd at elevated CO2 were acclimated to elevated CO2. Notably, elevated CO2 promoted the accumulation of stress-responsive and senescence-associated amino acid markers in gwd plants. The results presented in this work provide evidence that under long-day conditions, temporary storage of overflow photosynthate as starch negatively affect Rubisco performance. These data are consistent with earlier hypothesis that photosynthetic acclimation can be caused by accelerated senescence and hindrance of CO2 diffusion to the stroma due to accumulation of large starch granules.
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Estudio del aprovechamiento de los recursos pascícolas de los montes de Urbasa y Andía por parte del ganado equino extensivo. Propuestas de mejora
(2007) Jáuregui Mosquera, Iván; Escuela Técnica Superior de Ingenieros Agrónomos; Nekazaritza Ingeniarien Goi Mailako Eskola Teknikoa
Open Access
Short-term exposure to high atmospheric vapor pressure deficit (Vpd) severely impacts durum wheat carbon and nitrogen metabolism in the absence of edaphic water stress
(MDPI, 2021) Fakhet, Dorra; Morales Iribas, Fermín; Jáuregui Mosquera, Iván; Erice, G.; Aparicio Tejo, Pedro María; González Murua, Carmen; Aranjuelo Michelena, Iker; Aroca, Ricardo; Irigoyen, Juan J.; Ciencias; Zientziak
Low atmospheric relative humidity (RH) accompanied by elevated air temperature and decreased precipitation are environmental challenges that wheat production will face in future decades. These changes to the atmosphere are causing increases in air vapor pressure deficit (VPD) and low soil water availability during certain periods of the wheat-growing season. The main objective of this study was to analyze the physiological, metabolic, and transcriptional response of carbon (C) and nitrogen (N) metabolism of wheat (Triticum durum cv. Sula) to increases in VPD and soil water stress conditions, either alone or in combination. Plants were first grown in well-watered conditions and near-ambient temperature and RH in temperature-gradient greenhouses until anthesis, and they were then subjected to two different water regimes well-watered (WW) and water-stressed (WS), i.e., watered at 50% of the control for one week, followed by two VPD levels (low, 1.01/0.36 KPa and high, 2.27/0.62 KPa; day/night) for five additional days. Both VPD and soil water content had an important impact on water status and the plant physiological apparatus. While high VPD and water stress-induced stomatal closure affected photosynthetic rates, in the case of plants watered at 50%, high VPD also caused a direct impairment of the RuBisCO large subunit, RuBisCO activase and the electron transport rate. Regarding N metabolism, the gene expression, nitrite reductase (NIR) and transport levels detected in young leaves, as well as determinations of the δ15N and amino acid profiles (arginine, leucine, tryptophan, aspartic acid, and serine) indicated activation of N metabolism and final transport of nitrate to leaves and photosynthesizing cells. On the other hand, under low VPD conditions, a positive effect was only observed on gene expression related to the final step of nitrate supply to photosynthesizing cells, whereas the amount of15N supplied to the roots that reached the leaves decreased. Such an effect would suggest an impaired N remobilization from other organs to young leaves under water stress conditions and low VPD.