Aldo-keto reductase-1 (AKR1) protect cellular enzymes from salt stress by detoxifying reactive cytotoxic compounds

Abstract

Cytotoxic compounds like reactive carbonyl compounds such as methylglyoxal (MG), melandialdehyde (MDA), besides the ROS accumulate significantly at higher levels under salinity stress conditions and affect lipids and proteins that inhibit plant growth and productivity. The detoxification of these cytotoxic compounds by overexpression of NADPH-dependent Aldo-ketoreductase (AKR1) enzyme enhances the salinity stress tolerance in tobacco. The PsAKR1 overexpression plants showed higher survival and chlorophyll content and reduced MDA, H2O2, and MG levels under NaCl stress. The transgenic plants showed reduced levels of Na levels in both root and shoot due to reduced reactive carbonyl compounds (RCCs) and showed enhanced membrane stability resulted in higher root growth and biomass. The increased levels of antioxidant glutathione and enhanced activity of superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) suggest AKR1 could protect these enzymes from the RCC induced protein carbonylation by detoxification process. The transgenics also showed higher activity of delta 1-pyrroline-5- carboxylate synthase (P5CS) enzyme resulted in increasedproline levels to maintain osmotic homeostasis. The results demonstrates that the AKR1 protects proteins or enzymes that are involved in scavenging of cytotoxic compounds by detoxifying RCCs generated under salinity stress.

PpAKR1A, a Novel Aldo-Keto Reductase from Physcomitrella Patens, Plays a Positive Role in Salt Stress

“…The increased concentrations of H 2 O 2 in ppakr1a mutants might be attributable to RCS-mediated decreases in the activities of SOD, CAT and POD. Our results were similar to those of a previous study in which AKR appeared to mediate salt tolerance by detoxifying RCS and thus maintaining ROS homeostasis [34]. In other words, PpAKR1A may decrease the level of RCS, which could in turn help to maintain the activity of ROS scavenging enzymes to reduce the level of ROS.…”

“…AKRs contribute to salinity tolerance by detoxifying RCS [12,19,34]. Therefore, we measured the concentrations of MG and MDA in the mutant and WT plants under salt conditions.…”

“…During treatment with 150 or 300 mM NaCl, a transgenic tobacco strain engineered to overexpress PsAKR1 exhibited low concentrations of Na + ions and highly stable membranes in the root and shoot, resulting in increases in the root growth and biomass. Additionally, PsAKR1 -overexpressing plants exhibited increased survival and decreased concentrations of MDA, H 2 O 2 and MG in response to NaCl treatment [34]. However, few studies have explored the function of AKR1 in plants.…”

“…The concentrations of total chlorophyll, MG, MDA and H 2 O 2 are known as important physiological indicators of plant stress resistance [17,42,43,44]. Previous studies observed much higher concentrations of total chlorophyll and much lower concentrations of MG, MDA, and H 2 O 2 in transgenic plants engineered to overexpress AKRs than in WT plants during salt stress [33,34]. These patterns indicate that AKRs are responsible for RCS detoxification in plants, and thereby improve resistance to salt stress.…”

A concise appraisal of lipid oxidation and lipoxidation in higher plants

“…Alternatively, some of these key enzymes have been disrupted in their action for comparison purposes by means of the construction of DNA-tagged knockout, or RNA interference mutants. Some of these key enzymes include aldehyde dehydrogenases [40], [67], [73], [78], [101], [110], Alkenal Oxidoreductase (AOR) [83], aldo-keto-reductase [87], [88], [91] and myo-inositol-O-methyltransferase (Imt1) [106], among others. Although most of these studies have been performed in Arabidopsis thaliana , these assays are being extended to plants of further agronomical interest, as initially performed in groundnut [60] by the creation of transgenic plants co-expressing aldo-keto reductase (AKR1) and protein L-isoaspartyl methyltransferase (PIMT2), or in rice and tobacco plants overexpressing AKR1 [61].…”