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Jáuregui Mosquera, Iván

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Jáuregui Mosquera

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Iván

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Ciencias

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0000-0002-6958-6746

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810433

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Now showing 1 - 4 of 4
  • PublicationOpen 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.
  • PublicationOpen 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.
  • PublicationOpen 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.
  • PublicationOpen 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].