Methylglyoxal, Triose Phosphate Isomerase, and Glyoxalase Pathway: Implications in Abiotic Stress and Signaling in Plants

Abstract

Methylglyoxal (MG) is a cytotoxic metabolite inevitably produced as a side product of primary metabolic pathways via both enzymatic and non-enzymatic reactions. In plants, spontaneous generation of MG through breakdown of triose sugars (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate) is believed to be the major route for MG formation. MG is maintained at basal levels in plants under normal conditions that accumulate to higher concentrations under various stresses, probably as a general consequence of all abiotic stresses. The toxic effects of MG is due to its ability to induce oxidative stress in cells, either directly through increased generation of reactive oxygen species (ROS) or indirectly via advanced glycation end product (AGE) formation. Thus, elevated MG levels have implications in inhibition of growth and development in plants. To keep MG levels in check, the two-step glyoxalase pathway comprising glyoxalase I (GLYI) and glyoxalase II (GLYII) enzymes has evolved as the major MG-scavenging detoxifi cation system that converts MG to D -lactate using glutathione as a cofactor in this process. Over-expression of glyoxalase pathway has been shown to confer tolerance to multiple stresses that works by controlling MG levels and maintaining glutathione homeostasis in plants. Moreover, increased activity of triose phosphate isomerase under different stresses that use up triose sugars via glycolysis further prevents MG levels from accumulating in the system along with increasing the energy status of plants. Considering the fact that MG levels are maintained at a threshold concentration in plants even under physiological conditions and also observed MG-dependent induction in expression

Proteomics provides insights into biological pathways altered by plant growth promoting bacteria and arbuscular mycorrhiza in sorghum grown in marginal soil

“…The 26S proteasome is known to degrade proteins including damaged proteins tagged with ubiquitin and also confers tolerance to various stresses (Kurepa et al 2009;Ueda et al 2011). Triose phosphate isomerase levels have been reported to increase under different stresses to prevent accumulation of cytotoxic metabolites (Kaur et al 2015). Triose phosphate isomerase is involved in glycolytic pathway, pentose phosphate pathway and carbon metabolism and distribution (Dorion et al 2012) and sugar metabolism (Ito et al 2003).…”

Methylglyoxal: An Emerging Signaling Molecule in Plant Abiotic Stress Responses and Tolerance

“…leaves or roots), and the physiological state of the whole plant ( Kaur et al, 2015a , b ). Spontaneous production of MG occurs as a consequence of glycolysis, in metabolically active plant cells, from the reaction of the triose sugar phosphates glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP), both of which are photosynthetic intermediates ( Yadav et al, 2005a ; Takagi et al, 2014 ; Kaur et al, 2015a , b ). This reaction is considered to be the principal route for MG formation under normal physiological conditions ( Figure 1 ).…”

“…The reactive alpha-ketoaldehyde MG is cytotoxic to plant cells at high cellular concentrations, but it may act as an important signaling molecule at low concentrations ( Yadav et al, 2005a , b ; Singla-Pareek et al, 2006 ; Hossain et al, 2009 ; Kaur et al, 2015a , b ). MG is produced in plant cells as a result of glycolysis, and its celluar concentrations are maintained at very low levels in the absence of any environmental stress ( Kaur et al, 2015b ). However, in response to abiotic stressors celluar concentrations of MG rapidly increase ( Yadav et al, 2005a , b ).…”

From methylglyoxal to pyruvate: a genome-wide study for the identification of glyoxalases and D-lactate dehydrogenases in Sorghum bicolor

“…The production of MG in response to various environmental cues and its subsequent detoxification by the glyoxalase pathway, together with its ability to trigger a widespread plant response, makes MG and glyoxalases suitable biomarkers for stress tolerance [15]. A large volume of evidence resulting from in vivo and in silico studies has revealed MG to be a central metabolite controlling signal transduction, gene expression and protein modification [16,17]. To date, several genome-wide analyses have been carried out that located the presence of multiple glyoxalase isoforms in all the plant species studied.…”

“…To date, several genome-wide analyses have been carried out that located the presence of multiple glyoxalase isoforms in all the plant species studied. A total of 11 GLYI and 5 GLYII genes in Arabidopsis thaliana [18], 11 GLYI and 3 GLYII in Oryza sativa [18], 24 GLYI and 12 GLYII in Glycine max [19], 29 GLYI and 14 GLYII in Medicago truncatula [20] and, 16 GLYI and 15 GLYII in Brassica rapa [21] have been identified. Fig.…”