Alleviation of microplastic toxicity in soybean by arbuscular mycorrhizal fungi: Regulating glyoxalase system and root nodule organic acid.

Microplastic accumulation in the soil-plant system can stress plants and affect products quality. Currently, studies on the effect of microplastics on plants are not consistent and underlying molecular mechanisms are yet unknown. Here for the first time, we performed a study to explore the molecular mechanism underlying the growth of soybean plants in soil contaminated with various types of microplastics (PS and HDPE) and arbuscular mycorrhizal fungi (AMF) (presence/absence). Our results revealed that a dose-dependent decline was observed in plant growth, chlorophyll content, and yield of soybean under MPs stress. The addition of MPs resulted in oxidative stress closely related to hydrogen peroxide generation (H2O2), methylglyoxal (MG) levels, lipid peroxidation (MDA), and lipoxygenase (LOX). In contrast, MPs addition enhanced mycorrhizal colonization and dependency relative to control while the rubisco and root activity declined. All the genes (GmHMA13 and GmHMA19) were downregulated in the presence of MPs except GmHMA18 in roots. AMF inoculation alleviated MPs-induced phytotoxic effects on colonization, rubisco activity, root activity and restored the growth of soybean. Under MPs exposure, AMF inoculation induced plant defense system via improved regulation of antioxidant enzymes, ascorbate, glutathione pool, and glyoxalase system. AMF upregulated the genes responsible for metals uptake in soybean under MPs stress. The antioxidant and glyoxalase systems coordinated regulation expressively inhibited the oxidative and carbonyl stress at both MPs types. Hence, AMF inoculation may be considered an effective approach for minimizing MPs toxicity and its adverse effects on growth of soybean grown on MPs-contaminated soils.

Strigolactone decreases cadmium concentrations by regulating cadmium localization and glyoxalase defense system: Effects on nodules organic acids and soybean yield.

To decrease environmental and human health risks associated with crop and soil contamination, alternative solutions are still needed. The information on strigolactones (SLs)-mediated elicitation of abiotic stress signaling and triggering physiological alterations is scarce in the plant. To unravel the same, soybean plants were subjected to cadmium (Cd) stress (20 mg kg-1), presence or absence of foliar applied SL (GR24) at the concentration of 10 µM. Excess Cd accumulation causes reduced growth (-52% shoot and +24% root), yield (-35%), physio-biochemical markers, organic acid production, and genes encoding heavy metal resilience in soybean. SL exogenous application decreased the growth and yield suppression (-12%), shielded chlorophyll (+3%), and prominently declined Cd-induced oxidative stress biomarkers accumulation in soybean. Moreover, SL effectively alleviates Cd-induced suppression in organic acids, superoxide dismutase (+73%), catalase activities (+117%), and increments ascorbate glutathione (ASA-GSH) cycle activities comprising ascorbate peroxidase, glutathione peroxidase, glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase. SL-mediated upregulation of genes encoding heavy metals tolerance and glyoxalase defense system in Cd stressed plants. The results of this work point out that SL could be a promising player in mitigating Cd-induced injuries effectively in soybean. It acts through the antioxidant system modulation for redox homeostasis, shielding chloroplasts, enhancing photosynthetic apparatus, and elevating organic acid production in soybean plants.