Zulet González, Ainhoa

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https://academica-e.unavarra.es/handle/2454/50219

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Zulet González

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Ainhoa

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Ciencias del Medio Natural

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0000-0003-3714-3825

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750640

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811122

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2017 - 20192
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Author: Fernández Escalada, Manuel × Subject: Aromatic amino acid pathway ×

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    PublicationOpen Access
    Effects of EPSPS Copy Number Variation (CNV) and glyphosate application on the aromatic and branched chain amino acid synthesis pathways in Amaranthus palmeri
    (Frontiers Media, 2017) Fernández Escalada, Manuel; Zulet González, Ainhoa; Gil Monreal, Miriam; Zabalza Aznárez, Ana; Ravet, Karl; Gaines, Todd; Royuela Hernando, Mercedes; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
    A key enzyme of the shikimate pathway, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS; EC 2.5.1.19), is the known target of the widely used herbicide glyphosate. Glyphosate resistance in Amaranthus palmeri, one of the most troublesome weeds in agriculture, has evolved through increased EPSPS gene copy number. The aim of this work was to study the pleiotropic effects of (i) EPSPS increased transcript abundance due to gene copy number variation (CNV) and of (ii) glyphosate application on the aromatic amino acid (AAA) and branched chain amino acid (BCAA) synthesis pathways. Hydroponically grown glyphosate sensitive (GS) and glyphosate resistant (GR) plants were treated with glyphosate 3 days after treatment. In absence of glyphosate treatment, high EPSPS gene copy number had only a subtle effect on transcriptional regulation of AAA and BCAA pathway genes. In contrast, glyphosate treatment provoked a general accumulation of the transcripts corresponding to genes of the AAA pathway leading to synthesis of chorismate in both GS and GR. After chorismate, anthranilate synthase transcript abundance was higher while chorismate mutase transcription showed a small decrease in GR and remained stable in GS, suggesting a regulatory branch point in the pathway that favors synthesis toward tryptophan over phenylalanine and tyrosine after glyphosate treatment. This was confirmed by studying enzyme activities in vitro and amino acid analysis. Importantly, this upregulation was glyphosate dose dependent and was observed similarly in both GS and GR populations. Glyphosate treatment also had a slight effect on the expression of BCAA genes but no general effect on the pathway could be observed. Taken together, our observations suggest that the high CNV of EPSPS in A. palmeri GR populations has no major pleiotropic effect on the expression of AAA biosynthetic genes, even in response to glyphosate treatment. This finding supports the idea that the fitness cost associated with EPSPS CNV in A. palmeri may be limited.
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    PublicationOpen Access
    Enhancement of glyphosate efficacy on Amaranthus palmeri by exogenous quinate application
    (Elsevier, 2019) Zulet González, Ainhoa; Fernández Escalada, Manuel; Zabalza Aznárez, Ana; Royuela Hernando, Mercedes; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
    Glyphosate is a widely used herbicide targeting the enzyme 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) in the aromatic amino acid biosynthesis pathway (shikimate pathway) and provoking accumulation of quinate, a secondary metabolite synthesized through a side branch of this pathway. The objective of this work was to evaluate whether the efficacy of glyphosate activity in Amaranthus palmeri is enhanced by quinate application one day after herbicide treatment. To this end, one glyphosate-sensitive and one glyphosate-resistant (due to EPSPS gene amplification) population of A. palmeri were used. The 3- day time course study of the quinate treatment alone showed quinate, Tyr and Phe accumulation in both populations. When the herbicide was applied alone at 0.25× the recommended dose, no phytotoxicity or glyphosate effects were detected in the sensitive population 3 days after treatment, but the combined treatment with quinate was lethal, and markers of herbicide activity at the amino acid level could be detected. In the resistant population, an important metabolic perturbation in the flux of the shikimate pathway was detected in the combined treatment. These results raise the possibility of the joint application of quinate and glyphosate to enhance glyphosate efficacy while lowering doses in the sensitive population.