A glutathione-independent DJ-1/Pfp1 domain containing glyoxalase III, OsDJ-1C, functions in abiotic stress adaptation in rice

MAIN CONCLUSION

Overexpression of OsDJ-1C in rice improves root architecture, photosynthesis, yield and abiotic stress tolerance through modulating methylglyoxal levels, antioxidant defense, and redox homeostasis. Exposure to abiotic stresses leads to elevated methylglyoxal (MG) levels in plants, impacting seed germination and root growth. In response, the activation of NADPH-dependent aldo-keto reductase and glutathione (GSH)-dependent glyoxalase enzymes helps to regulate MG levels and reduce its toxic effects. However, detoxification may not be carried out effectively due to the limitation of GSH and NADPH in plants under stress. Recently, a novel enzyme called glyoxalase III (GLY III) has been discovered which can detoxify MG in a single step without needing GSH. To understand the physiological importance of this pathway in rice, we overexpressed the gene encoding GLYIII enzyme (OsDJ-1C) in rice. It was observed that OsDJ-1C overexpression in rice regulated MG levels under stress conditions thus, linked well with plants' abiotic stress tolerance potential. The OsDJ-1C overexpression lines displayed better root architecture, improved photosynthesis, and reduced yield penalty compared to the WT plants under salinity, and drought stress conditions. These plants demonstrated an improved GSH/GSSG ratio, reduced level of reactive oxygen species, increased antioxidant capacity, and higher anti-glycation activity thereby indicating that the GLYIII mediated MG detoxification plays a significant role in plants' ability to reduce the impact of abiotic stress. Furthermore, these findings imply the potential of OsDJ-1C in crop improvement programs.

The antioxidant glutathione

Reduced glutathione (GSH) is an essential non-enzymatic antioxidant in mammalian cells. GSH can act directly as an antioxidant to protect cells against free radicals and pro-oxidants, and as a cofactor for antioxidant and detoxification enzymes such as glutathione peroxidases, glutathione S-transferases, and glyoxalases. Glutathione peroxidases detoxify peroxides by a reaction that is coupled to GSH oxidation to glutathione disulfide (GSSG). GSSG is converted back to GSH by glutathione reductase and cofactor NADPH. GSH can regenerate vitamin E following detoxification reactions of vitamin E with lipid peroxyl radicals (LOO). GSH is a cofactor for GST during detoxification of electrophilic substances and xenobiotics. Dicarbonyl stress induced by methylglyoxal and glyoxal is alleviated by glyoxalase enzymes and GSH. GSH regulates redox signaling through reversible oxidation of critical protein cysteine residues by S-glutathionylation. GSH is involved in other cellular processes such as protein folding, protecting protein thiols from oxidation and crosslinking, degradation of proteins with disulfide bonds, cell cycle regulation and proliferation, ascorbate metabolism, apoptosis and ferroptosis.

Maghemite nano-fertilization promotes fluoride tolerance in rice by restoring grain yield and modulating the ionome and physiome

The present manuscript elucidated the ameliorative potential of nano-maghemite (FeNPs) against the hazardous effects of fluoride toxicity in the sensitive rice cultivar, IR-64. Fluoride pollution triggered bioaccumulation in root, shoot and spikelets which inhibited reproduction, agronomic development and mineral uptake. Suppressed activity of enzymatic antioxidants and excessive cobalt translocation manifested severe ROS-induced oxidative injuries. Seedling priming with FeNPs reduced fluoride bioaccumulation and promoted efficient uptake of macroelements and micronutrients like potassium, calcium, iron, zinc, copper, nickel, manganese, selenium and vanadium and reduced the translocation of cobalt in mature seedlings during stress. This altogether triggered growth and activated the enzymes like SOD, CAT, APX and GPOX. High accumulation of non-enzymatic antioxidants like proline, anthocyanins, flavonoids, phenolics along with stimulated GSH synthesis (determined from high GR, GST and GPX activity) and glyoxalase activity enabled FeNP-pulsed plants to efficiently scavenge ROS, O₂^-, H₂O₂ and methylglyoxal, and mitigate oxidative injuries. The ROS production was also lowered due to suppressed NADPH oxidase activity. This ensured subsequent revitalization of Hill activity and the level of photosynthetic pigments. Due to reduced fluoride partitioning and improved nutritional sink, the grain and panicle development in FeNP-primed, stressed seedlings were more stimulated than even control sets. Overall, our findings supported by statistical modelling established the potential of iron-nanotechnology in promoting safe rice cultivation even in fluoride-polluted environments.

Exogenous methylglyoxal enhances the reactive aldehyde detoxification capability and frost-hardiness of wheat

Cold-acclimation is essential for the development of adequate frost-hardiness in cereals and therefore sudden freezes can cause considerable damage to the canopy. However, timely adding of an appropriate signal in the absence of cold acclimation may also harden wheat for the upcoming freeze. The feasibility of the promising signal molecule methylglyoxal was tested here for such applications and the signal mechanism was studied in bread wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. ssp. durum). Spraying with 10 mM methylglyoxal did not decrease the fresh weight and photosynthetic parameters in most wheat varieties at growth temperature (21 °C). Photosynthetic parameters even improved and chlorophyll content increased in some cases. Increased transcript level of glutathione-S-transferases and omega-3 fatty acid desaturases was detected by qPCR 6 h after the last methylglyoxal spray. Aldo-keto reductase and glyoxalase enzyme activities, as well as sorbitol content of wheat plants increased 24 h after the last 10 mM methylglyoxal spray in most of the cultivars. These mechanisms may explain the increased freezing survival of methylglyoxal pretreated wheat plants from less than 10% to over 30%. Our results demonstrate that exogenous methylglyoxal treatment can be safely added to wheat plants as preparatory treatment without detrimental effects but inducing some of the stress-protective mechanisms, which contribute to frost-hardiness.

Glyoxalases in Urological Malignancies

Urological cancers include a spectrum of malignancies affecting organs of the reproductive and/or urinary systems, such as prostate, kidney, bladder, and testis. Despite improved primary prevention, detection and treatment, urological cancers are still characterized by an increasing incidence and mortality worldwide. While advances have been made towards understanding the molecular bases of these diseases, a complete understanding of the pathological mechanisms remains an unmet research goal that is essential for defining safer pharmacological therapies and prognostic factors, especially for the metastatic stage of these malignancies for which no effective therapies are currently being used. Glyoxalases, consisting of glyoxalase 1 (Glo1) and glyoxalase 2 (Glo2), are enzymes that catalyze the glutathione-dependent metabolism of cytotoxic methylglyoxal (MG), thus protecting against cellular damage and apoptosis. They are generally overexpressed in numerous cancers as a survival strategy by providing a safeguard through enhancement of MG detoxification. Increasing evidence suggests that glyoxalases, especially Glo1, play an important role in the initiation and progression of urological malignancies. In this review, we highlight the critical role of glyoxalases as regulators of tumorigenesis in the prostate through modulation of various critical signaling pathways, and provide an overview of the current knowledge on glyoxalases in bladder, kidney and testis cancers. We also discuss the promise and challenges for Glo1 inhibitors as future anti-prostate cancer (PCa) therapeutics and the potential of glyoxalases as biomarkers for PCa diagnosis.

Recent findings on the physiological function of DJ-1: Beyond Parkinson's disease

Several mutations in the gene coding for DJ-1 have been associated with early onset forms of parkinsonism. In spite of the massive effort spent by the scientific community in understanding the physiological role of DJ-1, a consensus on what DJ-1 actually does within the cells has not been reached, with several diverse functions proposed. At present, the most accepted function for DJ-1 is a neuronal protective role against oxidative stress. However, how exactly this function is exerted by DJ-1 is not clear. In recent years, novel molecular mechanisms have been suggested that may account for the antioxidant properties of DJ-1. In this review, we critically analyse the experimental evidence, including some very recent findings, supporting the purported neuroprotective role of DJ-1 through different mechanisms linked to oxidative stress handling, as well as the relevance of these processes in the context of Parkinson's disease.