METABOLISMO DE OXIMAS INDOLICAS Y POLIAMINAS, Y SU FUNCION SEÑALIZADORA EN PLANTAS BAJO DIFERENTES TIPOS DE NUTRICION NITROGENADA DURANTE EL DESARROLLO Y LA RESPUESTA A ESTRES

AGL2017-86293-P

Nombre agencia financiadora Agencia Estatal de Investigación
Acrónimo agencia financiadora AEI
Programa Programa Estatal de Fomento de la Investigación Científica y Técnica de Excelencia
Subprograma Subprograma Estatal de Generación de Conocimiento
Convocatoria Proyectos I+D
Año convocatoria 2017
Unidad de gestión Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016
Centro beneficiario UNIVERSIDAD PUBLICA DE NAVARRA
Identificador persistente http://dx.doi.org/10.13039/501100011033

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Polyamines and oximes in the tolerance response against ammonium stress in plants

Academica-e. Repositorio Institucional de la Universidad Pública de Navarra
  • Urra Rodríguez, Marina
Several studies have uncovered ammonium-triggered physiological responses
in plants, such as changes in cation homeostasis, content of nitrogen-rich
molecules with low carbon/nitrogen ratio, redox status and metabolism, gene
expression, pH, and phytohormone balance. In this work, the relevance of the
urea cycle to polyamine metabolism in higher plants was demonstrated, since
these interconnected routes operated as important protective mechanisms
limiting ammonium toxicity in Medicago truncatula. Accordingly, high
ammonium resulted in the accumulation of ammonium and pathway
intermediates, particularly glutamine, arginine, ornithine, and putrescine. A
switch in the functioning of the urea cycle in roots, from the arginine
decarboxylase to the ornithine decarboxylase-dependent production of
putrescine, suggested that the ornithine decarboxylase enzyme may provide
greater plasticity to plants to cope with ammonium stress. Moreover, the
activity of copper amine oxidase, which releases ammonium from putrescine,
was significantly decreased in both shoots and roots, supported by in vitro
assays. Finally, transcript levels of urea cycle-related genes were increased and
those involved in polyamine catabolism were decreased under high
ammonium conditions. Early supplementation of plants with putrescine avoided ammonium
stress, preventing the ammonium-induced reduction of shoot and root
biomass, primary root growth, and photosynthetic performance index.
Exogenous putrescine increased nitrogen isotopic discrimination, indicating
not only that putrescine may not impede ammonia entrance, but also the
occurrence of an additional isotopic discrimination process as ammonium
assimilation. In fact, exogenous putrescine boosted glutamine content and
glutamine synthetase1 protein content and transcript levels in roots,
supporting that ammonium assimilation was upregulated in the presence of putrescine to avoid the translocation of excess ammonium to shoots. The
content of glutamine synthetase2 was decreased in shoots of putrescinetreated plants, which may indicate a lessening of acidic stress within
chloroplasts. Furthermore, exogenous putrescine regulated Snitrosoglutathione reductase enzyme and, thus, nitric oxide and Snitrosothiols contents. Considering the results obtained, a new model for the
role of putrescine under ammonium stress was proposed, where putrescine
may act as a negative regulator of nitric oxide accumulation, but promoting Snitrosoglutathione reductase activity and glutathione disulfide and ammonium
contents as plant tolerance response Due to the significance of maintaining nitric oxide homeostasis for
effectively dealing with ammonium stress, a potential oxidative source of nitric
oxide has been identified. The effect of the auxin precursor, indole-3-
acetaldoxime, may be attributed to its capacity to release nitric oxide from the
oximic moiety and to induce indole-3-acetic acid accumulation via indole-3-
acetaldoxime dehydratase, inhibiting primary root elongation and increasing
the number of secondary roots, arising a superroot phenotype. Due to the significance of maintaining nitric oxide homeostasis for
effectively dealing with ammonium stress, a potential oxidative source of nitric
oxide has been identified. The effect of the auxin precursor, indole-3-
acetaldoxime, may be attributed to its capacity to release nitric oxide from the
oximic moiety and to induce indole-3-acetic acid accumulation via indole-3-
acetaldoxime dehydratase, inhibiting primary root elongation and increasing
the number of secondary roots, arising a superroot phenotype., This PhD thesis has been funded by: predoctoral International Mobility Grant from the Government of Navarre 2022. Predoctoral Grant from the Government of Navarre 2020. State Program to Promote Scientific and Technical Research of Excellence – Subprogram for Generation of Knowledge AGL2017-86293-P., Programa de Doctorado en Agrobiología Ambiental (RD 99/2011), Ingurumen Agrobiologiako Doktoretza Programa (ED 99/2011)