Morán Juez, José Fernando

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https://academica-e.unavarra.es/handle/2454/49610

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Morán Juez

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José Fernando

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Ciencias

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IMAB. Research Institute for Multidisciplinary Applied Biology

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0000-0001-6621-6961

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88624

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3087

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2010 - 201912020 - 20221
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Author: Esteban Terradillos, Raquel × Subject: Ammonium stress ×

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    PublicationOpen Access
    The importance of the urea cycle and its relationships to polyamine metabolism during ammonium stress in Medicago truncatula
    (Oxford University Press, 2022) Urra Rodríguez, Marina; Buezo Bravo, Javier; Royo Castillejo, Beatriz; Cornejo Ibergallartu, Alfonso; López Gómez, Pedro; Cerdán Ruiz, Daniel; Esteban Terradillos, Raquel; Martínez Merino, Víctor; Gogorcena, Yolanda; Tavladoraki, Paraskevi; Morán Juez, José Fernando; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako Gobernuaren
    The ornithine–urea cycle (urea cycle) makes a signifcant contribution to the metabolic responses of lower photosynthetic eukaryotes to episodes of high nitrogen availability. In this study, we compared the role of the plant urea cycle and its relationships to polyamine metabolism in ammonium-fed and nitrate-fed Medicago truncatula plants. High ammonium resulted in the accumulation of ammonium and pathway intermediates, particularly glutamine, arginine, ornithine, and putrescine. Arginine decarboxylase activity was decreased in roots, suggesting that the ornithine decarboxylase-dependent production of putrescine was important in situations of ammonium stress. The activity of copper amine oxidase, which releases ammonium from putrescine, was signifcantly decreased in both shoots and roots. In addition, physiological concentrations of ammonium inhibited copper amine oxidase activity in in vitro assays, supporting the conclusion that high ammonium accumulation favors putrescine synthesis. Moreover, early supplementation of plants with putrescine avoided ammonium toxicity. The levels of transcripts encoding urea-cyclerelated proteins were increased and transcripts involved in polyamine catabolism were decreased under high ammonium concentrations. We conclude that the urea cycle and associated polyamine metabolism function as important protective mechanisms limiting ammonium toxicity in M. truncatula. These fndings demonstrate the relevance of the urea cycle to polyamine metabolism in higher plants.
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    PublicationOpen Access
    High irradiance induces photoprotective mechanisms and a positive effect on NH4+ stress in Pisum sativum L.
    (Elsevier, 2010-04-29) Ariz Arnedo, Idoia; Esteban Terradillos, Raquel; García Plazaola, José Ignacio; Becerril, José María; Aparicio Tejo, Pedro María; Morán Juez, José Fernando; Ciencias; Zientziak; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
    Photosynthesis provides plant metabolism with reduced carbon (C) but is also the main source of oxidative stress in plants. Likewise, high doses of NH4+ as sole N source have been reported to be toxic for most plants, resulting in reduced plant growth and restricting C availability. The combination of high photosynthetic photon flux densities (PPFD) and NH4+ nutrition may provide higher C availability but could also have a detrimental effect on the plants, therefore the objective of this study is to evaluate whether NH4+ induces photo-oxidative stress that is exacerbated under high light conditions. Pea plants (Pisum sativum cv. sugar-snap) were grown hydroponically with NH4+ (0.5, 2.5, 5 and 10 mM) under high (750 μmol photons m−2 s−1) or low PPFD conditions (350 μmol photons m−2 s−1). High PPFD contributes to a higher tolerance to ammonium by pea plants, as it originated higher biomass content due to higher photosynthetic rates. However, a deficit of N (0.5 and 2.5 mM NH4+) under high PPFD conditions caused an antioxidant response, as indicated by increased photoprotective pigment and chloroplastic superoxide dismutase contents. Plants grown with higher doses of N and high PPFD showed less need for photoprotection. An increase in the specific leaf weight (SLW) ratio was observed associated not only with high PPFDs but also with the highest NH4+ dose. Overall, these results demonstrate that, despite the activation of some photoprotective responses at high PPFD, there were no photoinhibitory symptoms and a positive effect on NH4+ toxicity, thus suggesting that the harmful effects of NH4+ are not directly related to the generation of photo-oxidative stress.