Open Access
ERF-VII transcription factors induce ethanol fermentation in response to amino acid biosynthesis-inhibiting herbicides
(Oxford University Press, 2019) Gil Monreal, Miriam; Giuntoli, Beatrice; Zabalza Aznárez, Ana; Licausi, Francesco; Royuela Hernando, Mercedes; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Herbicides inhibiting either aromatic or branched-chain amino acid biosynthesis trigger similar physiological responses in plants, despite their different mechanism of action. Both types of herbicides are known to activate ethanol fermentation by inducing the expression of fermentative genes; however, the mechanism of such transcriptional regulation has not been investigated so far. In plants exposed to low-oxygen conditions, ethanol fermentation is transcriptionally controlled by the ethylene response factors-VII (ERF-VIIs), whose stability is controlled in an oxygen-dependent manner by the Cys-Arg branch of the N-degron pathway. In this study, we investigated the role of ERF-VIIs in the regulation of the ethanol fermentation pathway in herbicide-treated Arabidopsis plants grown under aerobic conditions. Our results demonstrate that these transcriptional regulators are stabilized in response to herbicide treatment and are required for ethanol fermentation in these conditions. We also observed that mutants with reduced fermentative potential exhibit higher sensitivity to herbicide treatments, thus revealing the existence of a mechanism that mimics oxygen deprivation to activate metabolic pathways that enhance herbicide tolerance. We speculate that this signaling pathway may represent a potential target in agriculture to affect tolerance to herbicides that inhibit amino acid biosynthesis.
Open Access
Unravelling the phytotoxic effects of glyphosate on sensitive and resistant Amaranthus Palmeri populations by GC-MS and LC-MS metabolic profiling
(MDPI, 2023) Zulet González, Ainhoa; Gorzolka, Karin; Döll, Stefanie; Gil Monreal, Miriam; Royuela Hernando, Mercedes; Zabalza Aznárez, Ana; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Glyphosate, the most successful herbicide in history, specifically inhibits the activity of the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS; EC 2.5.1.19), one of the key enzymes in the shikimate pathway. Amaranthus palmeri is a driver weed in agriculture today that has evolved glyphosate-resistance through increased EPSPS gene copy number and other mechanisms. Non-targeted GC–MS and LC–MS metabolomic profiling was conducted to examine the innate physiology and the glyphosate-induced perturbations in one sensitive and one resistant (by EPSPS amplification) population of A. palmeri. In the absence of glyphosate treatment, the metabolic profile of both populations was very similar. The comparison between the effects of sublethal and lethal doses on sensitive and resistant populations suggests that lethality of the herbicide is associated with an amino acid pool imbalance and accumulation of the metabolites of the shikimate pathway upstream from EPSPS. Ferulic acid and its derivatives were accumulated in treated plants of both populations, while quercetin and its derivative contents were only lower in the resistant plants treated with glyphosate.
Open Access
Characterization of the Amaranthus palmeri physiological response to glyphosate in susceptible and resistant populations
(American Chemical Society, 2016) Fernández Escalada, Manuel; Gil Monreal, Miriam; Zabalza Aznárez, Ana; Royuela Hernando, Mercedes; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The herbicide glyphosate inhibits the plant enzyme 5-enolpyruvylshikimate3-phosphate synthase (EPSPS) in the aromatic amino acid (AAA) biosynthetic pathway. The physiologies of an Amaranthus palmeri population exhibiting resistance to glyphosate by EPSPS gene amplification (NC-R) and a susceptible population (NC-S) were compared. The EPSPS copy number of NC-R plants was 47.5-fold the copy number of NC-S plants. Although the amounts of EPSPS protein and activity were higher in NC-R plants than in NC-S plants, the AAA concentrations were similar. The increases in total free amino acid and in AAA contents induced by glyphosate were more evident in NC-S plants. In both populations, the EPSPS protein increased after glyphosate exposure, suggesting regulation of gene expression. EPSPS activity seems tightly controlled in vivo. Carbohydrate accumulation and a slight induction of ethanol fermentation were detected in both populations.
Open Access
Cysteine proteases are activated in sensitive Amaranthus palmeri populations upon treatment with herbicides inhibiting amino acid biosynthesis
(Wiley, 2023) Barco Antoñanzas, María; Font Farre, María; Eceiza, Mikel Vicente; Gil Monreal, Miriam; Van der Hoorn, Reiner; Royuela Hernando, Mercedes; Zabalza Aznárez, Ana; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The herbicides glyphosate and pyrithiobac inhibit the enzyme 5-enolpyruvylshikimate3-phosphate synthase (EPSPS) in the aromatic amino acid biosynthetic pathway and acetolactate synthase (ALS) in the branched-chain amino acid biosynthetic pathway, respectively. Here we characterise the protease activity profiles of a sensitive (S), a glyphosate-resistant (GR) and a multiple-resistant (MR) population of Amaranthus palmeri in response to glyphosate and pyrithiobac. Amino acid accumulation and cysteine protease activities were induced with both herbicides in the S population and with pyrithiobac in the GR population, suggesting that the increase in cysteine proteases is responsible for the increased degradation of the available proteins and the observed increase in free amino acids. Herbicides did not induce any changes in the proteolytic activities in the populations with target-site resistance, indicating that this effect was only induced in sensitive plants.
Open Access
Role of oxidative stress in the physiology of sensitive and resistant Amaranthus palmeri populations treated with herbicides inhibiting acetolactate synthase
(Frontiers Media, 2023) Eceiza, Mikel Vicente; Barco Antoñanzas, María; Gil Monreal, Miriam; Huybrechts, Michiel; Zabalza Aznárez, Ana; Cuypers, Ann; Royuela Hernando, Mercedes; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The aim of the present study was to elucidate the role of oxidative stress in the mode of action of acetolactate synthase (ALS) inhibiting herbicides. Two populations of Amaranthus palmeri S. Watson from Spain (sensitive and resistant to nicosulfuron, due to mutated ALS) were grown hydroponically and treated with different rates of the ALS inhibitor nicosulfuron (one time and three times the field recommended rate). Seven days later, various oxidative stress markers were measured in the leaves: H2O2, MDA, ascorbate and glutathione contents, antioxidant enzyme activities and gene expression levels. Under control conditions, most of the analysed parameters were very similar between sensitive and resistant plants, meaning that resistance is not accompanied by a different basal oxidative metabolism. Nicosulfuron-treated sensitive plants died after a few weeks, while the resistant ones survived, independently of the rate. Seven days after herbicide application, the sensitive plants that had received the highest nicosulfuron rate showed an increase in H2O2 content, lipid peroxidation and antioxidant enzymatic activities, while resistant plants did not show these responses, meaning that oxidative stress is linked to ALS inhibition. A supralethal nicosulfuron rate was needed to induce a significant oxidative stress response in the sensitive population, providing evidence that the lethality elicited by ALS inhibitors is not entirely dependent on oxidative stress.
Open Access
Increased glyphosate-induced gene expression in the shikimate pathway is abolished in the presence of aromatic amino acids and mimicked by shikimate
(Frontiers Media, 2020) Zulet González, Ainhoa; Barco Antoñanzas, María; Gil Monreal, Miriam; Royuela Hernando, Mercedes; Zabalza Aznárez, Ana; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The herbicide glyphosate inhibits the plant enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in the aromatic amino acid (AAA) biosynthetic pathway, also known as the shikimate pathway. Amaranthus palmeri is a fast-growing weed, and several populations have evolved resistance to glyphosate through increased EPSPS gene copy number. The main objective of this study was to elucidate the regulation of the shikimate pathway and determine whether the regulatory mechanisms of glyphosate-sensitive and glyphosate-resistant plants were different. Leaf disks of sensitive and resistant (due to EPSPS gene amplification) A. palmeri plants were incubated for 24 h with glyphosate, AAA, glyphosate + AAA, or several intermediates of the pathway: shikimate, quinate, chorismate and anthranilate. In the sensitive population, glyphosate induced shikimate accumulation and induced the gene expression of the shikimate pathway. While AAA alone did not elicit any change, AAA applied with glyphosate abolished the effects of the herbicide on gene expression. It was not possible to fully mimic the effect of glyphosate by incubation with any of the intermediates, but shikimate was the intermediate that induced the highest increase (three-fold) in the expression level of the genes of the shikimate pathway of the sensitive population. These results suggest that, in this population, the lack of end products (AAA) of the shikimate pathway and shikimate accumulation would be the signals inducing gene expression in the AAA pathway after glyphosate application. In general, the effects on gene expression detected after the application of the intermediates were more severe in the sensitive population than in the resistant population. These results suggest that when EPSPS is overexpressed, as in the resistant population, the regulatory mechanisms of the AAA pathway are disrupted or buffered. The mechanisms underlying this behavior remain to be elucidated.
Open Access
Nuevas tecnologías y materiales educativos digitales para la enseñanza y el aprendizaje de Biología y Geología
(2017) Gil Monreal, Miriam; González García, Esther; Facultad de Ciencias Humanas y Sociales; Giza eta Gizarte Zientzien Fakultatea
Las nuevas tecnologías ofrecen muchas oportunidades en la educación, y conscientes de ello, los gobiernos y distintas entidades privadas han desarrollado iniciativas para fomentar el uso de las Nuevas Tecnologías en las aulas. En este trabajo fin de máster, se ha realizado un análisis de las diferentes iniciativas desarrolladas en Navarra desde distintas organizaciones, con el fin de impulsar las Nuevas Tecnologías en los centros educativos de esta comunidad. Por otro lado, para conocer la situación actual en las aulas en cuanto a dotación de recursos digitales y para conocer cómo se perciben las Nuevas Tecnologías en la comunidad educativa, se realizaron sendas encuestas a los diferentes miembros de la comunidad educativa, profesores, alumnos y familias. Los resultados mostraron que, aunque hay cierta digitalización en las aulas, la dotación tecnológica es bastante básica. Por otro lado, se comprobó que la comunidad educativa está a favor del uso de Nuevas Tecnologías en las aulas, ya que éstas tienen mucho que ofrecer en el proceso enseñanza-aprendizaje. Finalmente, en el último capítulo de este trabajo, se presentan tres formatos de material educativo ofrecidos por distintas editoriales para la asignatura de Biología y Geología de 3ºESO. Este análisis nos muestra que las editoriales han modificado su oferta de material didáctico, introduciendo actividades más innovadoras que incluyen un cambio de metodología y dando mayor presencia a las Tecnologías de la Información y Comunicación. En conclusión, las Nuevas Tecnologías van teniendo mayor protagonismo en la educación, pero su introducción en las aulas está siendo muy lenta.
Open Access
The moderate oxidative stress induced by glyphosate is not detected in Amaranthus palmeri plants overexpressing EPSPS
(Elsevier, 2022) Gil Monreal, Miriam; Barco Antoñanzas, María; Zabalza Aznárez, Ana; Royuela Hernando, Mercedes; Eceiza, Mikel Vicente; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The present study aimed to determine whether glyphosate-induced oxidative stress is directly related to the action mechanism of this herbicide (5-enolpyruvylshikimate-3-phosphate synthase or EPSPS inhibition) and analyse the role of oxidative stress in glyphosate toxicity of the weed Amaranthus palmeri S. Wats. Two kinds of populations were studied using EPSPS amplification: glyphosate-sensitive and glyphosate-resistant (by gene amplification). Plants were grown hydroponically and treated with different glyphosate doses, after which several oxidative stress markers were measured in the leaves. Untreated, sensitive and resistant plants showed similar values for the analysed parameters. Treated glyphosate-sensitive plants showed an increase in shikimate, superoxide and H2O2 contents and dose-dependent lipid peroxidation and antioxidant responses; however, none of these effects were observed in resistant plants, indicating that glyphosate-induced oxidative stress is related to EPSPS inhibition. Oxidative stress is associated with an increase in the activity of peroxidases due to EPSPS inhibition, although the link between both processes remains elusive. The fact that some glyphosate doses were lethal but did not induce major oxidative damage provides evidence that glyphosate toxicity is independent of oxidative stress.
Open Access
Induction of the PDH bypass and upregulation of the ALDH7B4 in plants treated with herbicides inhibiting amino acid biosynthesis
(Elsevier, 2017) Gil Monreal, Miriam; Zabalza Aznárez, Ana; Missihoun, Tagnon D.; Dormann, Peter; Bartels, Dorothea; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Imazamox and glyphosate represent two classes of herbicides that inhibit the activity of acetohydroxyacid synthase in the branched-chain amino acid biosynthesis pathway and the activity of 5-enolpyruvylshikimate-3-phosphate synthase in the aromatic amino acid biosynthesis pathway, respectively. However, it is still unclear how imazamox and glyphosate lead to plant death. Both herbicides inhibit amino-acid biosynthesis and were found to induce ethanol fermentation in plants, but an Arabidopsis mutant deficient in alcohol dehydrogenase 1 was neither more susceptible nor more resistant than the wild-type to the herbicides. In this study, we investigated the effects of the amino acid biosynthesis inhibitors, imazamox and glyphosate, on the pyruvate dehydrogenase bypass reaction and fatty acid metabolism in A. thaliana. We found that the pyruvate dehydrogenase bypass was upregulated following the treatment by the two herbicides. Our results suggest that the Arabidopsis aldehyde dehydrogenase 7B4 gene might be participating in the pyruvate dehydrogenase bypass reaction. We evaluated the potential role of the aldehyde dehydrogenase 7B4 upon herbicide treatment in the plant defence mechanism. Plants that overexpressed the ALDH7B4 gene accumulated less soluble sugars, starch, and fatty acids and grew better than the wild-type after herbicide treatment. We discuss how the upregulation of the ALDH7B4 alleviates the effects of the herbicides, potentially through the detoxification of the metabolites produced in the pyruvate dehydrogenase bypass.
Open Access
Physiological approach to the use of the natural compound quinate in the control of sensitive and resistant Papaver rhoeas
(MDPI, 2020) Zabalza Aznárez, Ana; Zulet González, Ainhoa; Barco Antoñanzas, María; Eceiza, Mikel Vicente; Gil Monreal, Miriam; Royuela Hernando, Mercedes; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Quinate (1,3,4,5-tetrahydroxycyclohexanecarboxylate) is a compound synthesized in plants through a side-branch of the shikimate biosynthesis pathway, which is accumulated after glyphosate and acetolactate synthase inhibiting herbicides (ALS-inhibitors) and has phytotoxic potential. The objective of this study was to evaluate the phytotoxicity of quinate on several weed species. Among the species evaluated, Cynodon dactylon, Bromus diandrus, Lolium rigidum, Sinapis alba, and Papaver rhoeas, P. rhoeas was the most sensitive, and its growth was controlled with quinate concentrations above 100 mM at the phenological stage of 6–8 true leaves. A physiological study, including the shikimate pathway and the physiological markers of ALS-inhibitors (carbohydrates and amino acids), was performed in the sensitive and resistant plants treated with sulfonylureas or quinate. The typical physiological effects of ALS-inhibitors were detected in the sensitive population (free amino acid and carbohydrate accumulation) and not detected in the resistant population. The mode of action of quinate appeared to be related to general perturbations in their carbon/nitrogen metabolism rather than to specific changes in the shikimate pathway. These results suggest the possibility of using quinate in the weed control management of P. rhoeas.