Exogenous Glutamate Inhibits the Root Growth and Increases the Glutamine Content in Arabidopsis thaliana

Abstract

Previously, our work with ginseng hairy root shows that the tissue of low-branching and slow-growing phenotype contains high level of glutamine. In order to check if the high glutamine concentration inhibits the root growth, we applied exogenous glutamine or glutamate into growth medium and check the root growth of Arabidopsis. While glutamine did not affect root growth, over 0.1 mM glutamate inhibited severe root growth. However, when the amino acid solution was adjusted to pH 5.7 and added into medium, Arabidopsis seedlings show normal growth pattern on medium containing glutamate or aspartate. These results demonstrated that inhibition of the root growth by high concentration of exogenous glutamate was a result of the low pH toxicity caused by acidic amino acid, although low concentration (0.05 mM) of glutamate has an inhibitory effect on the primary root growth. The application of exogenous glutamine or glutamate increases glutamine concentration within root tissue about 3-to 4-fold. However, concentration of glutamate is not significantly increased. The KO mutant on each of the Gln1_1, Gln1_2, or Glu2 gene was little effective on the root growth. These results indicate that high concentration of endogenous glutamine observed in root tissue does not affect root growth.

A Novel Effect for Glycine on Root System Growth of Habanero Pepper

“…L-glutamate did not alter the root growth of the habanero pepper when compared with control with KCl ( Fig. 1A), which contrasts with what was previously reported for A. thaliana (Kim et al, 2010;Walch-Liu and Forde, 2008;Walch-Liu et al, 2006b).…”

“…Reportedly, the inhibitory effect of L-glutamate on the A. thaliana root could result from low pH toxicity because this effect was also caused by other acidic amino acids such as L-aspartate (Kim et al, 2010). We eliminated this possibility because glycine is a neutral amino acid and acidic amino acids did not affect habanero pepper growth.…”

“…Reports of amino acids affecting the root growth of Solanaceae family members, which include habanero pepper, are scarce and inconclusive, because they present limited data or contradictory effects (Kim et al, 2010;Street et al, 1960;Walch-Liu et al, 2006a).…”

Vanillin production in metabolically engineered Beta vulgaris hairy roots through heterologous expression of Pseudomonas fluorescens HCHL gene

“…It is however pertinent to mention that, even though the same mechanism probably operated to balance the starting pH of 3.0 to reach an equilibrium state of pH > 5.5 in either of the two root clones, but biomass increments were ∼four times lower in both the clones at pH 3.0 compared to that with the other two tested pH. The reduced biomass yield at low pH might be due to initial harsh treatment mediated damage of root cells, which consquently failed to recover normal growth potential even though the recovery of the equilibrium state of pH could be attained after gradual progression of the growth phase by calcium uptake as documented (Kim et al, 2009;Koyama et al, 2001).…”

Pharmacological Studies with Specific Agonist and Antagonist of Animal iGluR on Root Growth in Arabidopsis thaliana

“…As a signaling molecule, glutamate is regarded to be the major neurotransmitter in the mammalian central nervous system. The application of exogenous Glu can also alter root phenotype [31,32], indicating a role for GLR signaling in plants. Additionally, MEKK pathways can alter the glutamate sensitivity at the root tip suggesting for a glutamate signaling pathway in plants [33,34].…”