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Ariz Arnedo, Idoia

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Ariz Arnedo

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Idoia

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Ciencias

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0000-0003-3055-5560

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7826

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2016 - 20183
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Subject: Ammonium ×

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Now showing 1 - 3 of 3
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    PublicationOpen Access
    Mechanisms of ammonium toxicity and the quest for tolerance
    (Elsevier, 2016) Esteban Terradillos, Raquel; Ariz Arnedo, Idoia; Cruz, Cristina; Morán Juez, José Fernando; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
    Ammonium sensitivity of plants is a worldwide problem, constraining crop production. Prolonged application of ammonium as the sole nitrogen source may result in physiological and morphological disorders that lead to decreased plant growth and toxicity. The main causes of ammonium toxicity/tolerance described until now include high ammonium assimilation by plants and/or low sensitivity to external pH acidification. The various ammonium transport-related components, especially the non-electrogenic influx of NH3 (related to the depletion of 15N) and the electrogenic influx of NH4+, may contribute to ammonium accumulation, and therefore to NH3 toxicity. However, this accumulation may be influenced by increasing K+ concentration in the root medium. Recently, new insights have been provided by “omics” studies, leading to a suggested involvement of GDP mannose-pyrophosphorylase in the response pathways of NH4+ stress. In this review, we highlight the cross-talk signaling between nitrate, auxins and NO, and the importance of the connection of the plants’ urea cycle to metabolism of polyamines. Overall, the tolerance and amelioration of ammonium toxicity are outlined to improve the yield of ammonium-grown plants. This review identifies future directions of research, focusing on the putative importance of aquaporins in ammonium influx, and on genes involved in ammonium sensitivity and tolerance.
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    PublicationOpen Access
    Quantitative proteomics reveals the importance of nitrogen source to control glucosinolate metabolism in Arabidopsis thaliana and Brassica oleracea
    (Oxford University Press, 2016) Marino Bilbao, Daniel; Ariz Arnedo, Idoia; Lasa Larrea, Berta; Santamaría Martínez, Enrique; Aparicio Tejo, Pedro María; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
    Accessing different nitrogen (N) sources involves a profound adaptation of plant metabolism. In this study, a quantitative proteomic approach was used to further understand how the model plant Arabidopsis thaliana adjusts to different N sources when grown exclusively under nitrate or ammonium nutrition. Proteome data evidenced that glucosinolate metabolism was differentially regulated by the N source and that both TGG1 and TGG2 myrosinases were more abundant under ammonium nutrition, which is generally considered to be a stressful situation. Moreover, Arabidopsis plants displayed glucosinolate accumulation and induced myrosinase activity under ammonium nutrition. Interestingly, these results were also confirmed in the economically important crop broccoli (Brassica oleracea var. italica). Moreover, these metabolic changes were correlated in Arabidopsis with the differential expression of genes from the aliphatic glucosinolate metabolic pathway. This study underlines the importance of nitrogen nutrition and the potential of using ammonium as the N source in order to stimulate glucosinolate metabolism, which may have important applications not only in terms of reducing pesticide use, but also for increasing plants’ nutritional value.
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    PublicationOpen Access
    Nitrogen isotope signature evidences ammonium deprotonation as a common transport mechanism for the AMT-Mep-Rh protein superfamily
    (American Association for the Advancement of Science, 2018) Ariz Arnedo, Idoia; Boeckstaens, Mélanie; Gouveia, Catarina; Martins, Ana Paula; Sanz-Luque, Emanuel; Fernández, Emilio; Soveral, Graça; Wiren, Nicolaus von; Marini, Anna M.; Aparicio Tejo, Pedro María; Cruz, Cristina; Ciencias; Zientziak
    Ammonium is an important nitrogen (N) source for living organisms, a key metabolite for pH control, and a potent cytotoxic compound. Ammonium is transported by the widespread AMT-Mep-Rh membrane proteins, and despite their significance in physiological processes, the nature of substrate translocation (NH3/NH4+) by the distinct members of this family is still a matter of controversy. Using Saccharomyces cerevisiae cells expressing representative AMT-Mep-Rh ammonium carriers and taking advantage of the natural chemical-physical property of the N isotopic signature linked to NH4+/NH3 conversion, this study shows that only cells expressing AMT-Mep-Rh proteins were depleted in N-15 relative to N-14 when compared to the external ammonium source. We observed N-15 depletion over a wide range of external pH, indicating its independence of NH3 formation in solution. On the basis of inhibitor studies, ammonium transport by nonspecific cation channels did not show isotope fractionation but competition with K+. We propose that kinetic N isotope fractionation is a common feature of AMT-Mep-Rh-type proteins, which favor N-14 over N-15, owing to the dissociation of NH4+ into NH3+ H+ in the protein, leading to N-15 depletion in the cell and allowing NH3 passage or NH3/H+ cotransport. This deprotonation mechanism explains these proteins' essential functions in environments under a low NH4+/K+ ratio, allowing organisms to specifically scavenge NH4+. We show that N-15 isotope fractionation may be used in vivo not only to determine the molecular species being transported by ammonium transport proteins, but also to track ammonium toxicity and associated amino acids excretion.