Abstract
The glyoxalase pathway, which consists of the two enzymes, GLYOXALASE 1 (GLX 1) (E.C.: 4.4.1.5) and 2 (E.C.3.1.2.6), has a vital role in chemical detoxification. In Arabidopsis thaliana there are at least four different isoforms of glyoxalase 2, two of which, GLX2-1 and GLX2-4 have not been characterized in detail. Here, the functional role of Arabidopsis thaliana GLX2-1 is investigated. Glx2-1 loss-of-function mutants and plants that constitutively over-express GLX2-1 resemble wild-type plants under normal growth conditions. Insilico analysis of publicly available microarray datasets with ATTEDII, Mapman and Genevestigator indicate potential role(s) in stress response and acclimation. Results presented here demonstrate that GLX2-1 gene expression is up-regulated in wild type Arabidopsis thaliana by salt and anoxia stress, and by excess L-Threonine. Additionally, a mutation in GLX2-1 inhibits growth and survival during abiotic stresses. Metabolic profiling studies show alterations in the levels of sugars and amino acids during threonine stress in the plants. Elevated levels of polyamines, which are known stress markers, are also observed. Overall our results suggest that Arabidopsis thaliana GLX2-1 is not essential during normal plant life, but is required during specific stress conditions.
Highlights
The glyoxalase pathway has been identified in a wide range of organisms including mammals [1,2], plants [3,4], yeast [5] and protozoa [6]
In this report we show that Arabidopsis thaliana GLX2-1 is a non-essential gene, but that it plays an important role in stress response
GLX21 transcripts were absent from plants homozygous for the insert indicating the complete disruption of GLX2-1 (Figure S1)
Summary
The glyoxalase pathway has been identified in a wide range of organisms including mammals [1,2], plants [3,4], yeast [5] and protozoa [6]. The pathway consists of two enzymes, Lactoylglutathione lyase (GLX1, 4.4.1.5) and Hydroxyacyl glutathione hydrolase (GLX2, 3.1.2.6) [7,8]. This pathway is involved in chemical detoxification by converting acyclic alpha oxoaldehydes to their corresponding alpha hydroxyl acids [6,9,10]. Various 2-oxoaldehydes can be used as substrates, methylglyoxal is thought to be the primary substrate [7]. Methylglyoxal (MG) is produced primarily by the enzymatic and non-enzymatic elimination of phosphate from glycolytic intermediates, including dihydroxy acetone phosphate and glyceraldehyde-3- phosphate [11,12,13,14]. Other sources of MG include carbohydrate metabolism and lipid, acetone and threonine catabolism [15,16]
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