Stable Isotope Resolved Metabolomics Reveals the Role of Anabolic and Catabolic Processes in Glyphosate-Induced Amino Acid Accumulation in Amaranthus palmeri Biotypes

Abstract

Biotic and abiotic stressors often result in the buildup of amino acid pools in plants, which serve as potential stress mitigators. However, the role of anabolic (de novo amino acid synthesis) versus catabolic (proteolytic) processes in contributing to free amino acid pools is less understood. Using stable isotope-resolved metabolomics (SIRM), we measured the de novo amino acid synthesis in glyphosate susceptible (S-) and resistant (R-) Amaranthus palmeri biotypes. In the S-biotype, glyphosate treatment at 0.4 kg ae/ha resulted in an increase in total amino acids, a proportional increase in both (14)N and (15)N amino acids, and a decrease in soluble proteins. This indicates a potential increase in de novo amino acid synthesis, coupled with a lower protein synthesis and a higher protein catabolism following glyphosate treatment in the S-biotype. Furthermore, the ratio of glutamine/glutamic acid (Gln/Glu) in the glyphosate-treated S- and R-biotypes indicated that the initial assimilation of inorganic nitrogen to organic forms is less affected by glyphosate. However, amino acid biosynthesis downstream of glutamine is disproportionately disrupted in the glyphosate treated S-biotype. It is thus concluded that the herbicide-induced amino acid abundance in the S-biotype is contributed by both protein catabolism and de novo synthesis of amino acids such as glutamine and asparagine.

Glyphosate-Induced Specific and Widespread Perturbations in the Metabolome of Soil Pseudomonas Species

“…And, the significant depletion in tryptophan level was clustered with depletion of valine and thymidine (Figure 3). In accordance with our results, impairment of pathways involved in energy metabolism (Orcaray et al, 2012) and protein synthesis (Maroli et al, 2016) were found in glyphosate-treated plants. Intracellular accumulation of AAs and depletion in protein synthesis have been reported for the glyphosate-sensitive biotype of the flowering plant Amaranthus palmeri (Maroli et al, 2016).…”

“…In accordance with our results, impairment of pathways involved in energy metabolism (Orcaray et al, 2012) and protein synthesis (Maroli et al, 2016) were found in glyphosate-treated plants. Intracellular accumulation of AAs and depletion in protein synthesis have been reported for the glyphosate-sensitive biotype of the flowering plant Amaranthus palmeri (Maroli et al, 2016). This was proposed to be due to the metabolic response of the plant to the abiotic stressor (Maroli et al, 2016), which may include a decrease in de novo protein synthesis.…”

“…Intracellular accumulation of AAs and depletion in protein synthesis have been reported for the glyphosate-sensitive biotype of the flowering plant Amaranthus palmeri (Maroli et al, 2016). This was proposed to be due to the metabolic response of the plant to the abiotic stressor (Maroli et al, 2016), which may include a decrease in de novo protein synthesis. Thus, we attributed the significant accumulation of glutamine in the glyphosate-sensitive P. putida S12 to either inhibition of protein synthesis or disruption of other glutamine-consuming metabolic pathways by glyphosate (Figure 4).…”

Mechanism of Resistance to Glyphosate in Lolium perenne from Argentina

“…The effect of the herbicide is not restricted to the inhibition of aromatic amino acid biosynthesis alone. It also disrupts the de novo biosynthesis of most non-aromatic amino acids, coupled with decreased protein synthesis (Maroli et al, 2016). In consequence, growth is inhibited (Pline et al, 2002;Orcaray et al, 2012), the transport of assimilates is reduced (Yanniccari et al, 2012a) and photosynthetic CO 2 assimilation decreases significantly (Olesen and Cedergreen, 2010).…”

“…In consequence, growth is inhibited (Pline et al, 2002;Orcaray et al, 2012), the transport of assimilates is reduced (Yanniccari et al, 2012a) and photosynthetic CO 2 assimilation decreases significantly (Olesen and Cedergreen, 2010). Several of these effects are limited or absent in glyphosate-resistant weed plants treated with the herbicide (Yanniccari et al, 2012a,b,c;Maroli et al, 2016).…”