Effects of EPSPS Copy Number Variation (CNV) and glyphosate application on the aromatic and branched chain amino acid synthesis pathways in Amaranthus palmeri
Fecha
2017Autor
Versión
Acceso abierto / Sarbide irekia
Tipo
Artículo / Artikulua
Versión
Versión publicada / Argitaratu den bertsioa
Identificador del proyecto
ES/1PE/AGL2016-77531
Impacto
|
10.3389/fpls.2017.01970
Resumen
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 ...
[++]
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. [--]
Materias
Glyphosate,
Aromatic amino acid pathway,
Branched chain amino acid pathway,
mRNA relative expression,
EPSPS,
CM,
AS,
Amaranthus palmeri
Editor
Frontiers Media
Publicado en
Frontiers in Plant Science, 16 November 2017
Departamento
Universidad Pública de Navarra. Departamento de Ciencias del Medio Natural /
Nafarroako Unibertsitate Publikoa. Natura Ingurunearen Zientziak Saila
Versión del editor
Entidades Financiadoras
MF-E, AZ-G, and MG-M received funding from fellowships
trough Universidad Pública de Navarra. This work was financially
supported by a grant from the Ministerio Español de Economía
y Competitividad (AGL-2016-77531R). This work was also
partially financially supported by the USDA National Institute of
Food and Agriculture, Hatch project COL00719 to the Colorado
State University Agricultural Experiment Station.