Interplay of ZnONPs and/or SeNPs induces arsenic tolerance in soybean by regulation of antioxidants pool, WRKY genes, and expression of arsenic transporters

Abstract

Arsenic is a nonessential element that confers toxicity to plants. Excessive arsenic accumulation in food crops poses safety concerns for human and animal health. To date, our understanding of the alleviation mechanism of As(V) toxicity in soybean plant employing NP is less known. Thus, the objective of the present study was to evaluate the effectiveness of zinc oxid nanoparticle (ZnONP) and/or selenium nanoparticle (SeNP) treatment on arsenic stress in seedling of soybean (Glycine max [L] Merrill). Soybean seedlings were grown hydroponically in 10 liters pots, treated at V2 growth stage with arsenate (25 μM L−1), two concentrations of ZnONPs (25 μM and 50 μM L−1) and two concentrations of elemental SeNPs (10 μM and 25 μM L−1) separately and in tandem, and then kept for further 10 d. Positive control (T2) significantly induced electrolyte leakage (EL) and facilitated the accumulation of O2− and H2O2 in roots and leaf tissues, along with higher deposition of As in sensitive cell organs including cellular organelles and cell wall. The application of ZnONPs and SeNPs, both independently and in tandem, promoted the As compartmentalization into vacuole, reduced the EL and rescued plant health by enhanced the metal tolerance index (MTI). In addition, cellular toxicants (i.e., O2−, H2O2 and GSSG) were drastically reduced because of the steady increased in MDHAR, GSTs, GSH and PCs levels in response to the nanoparticles treatment than in positive control (T2). Moreover, Na+ K+ -ATPase and Ca++ Mg++ -ATPase activities were also induced in response to NPs treatment groups. All the nanoparticles treatment groups displayed elevated expression of TFs (GmWRKY6, GmWRKY46, GmWRKY56, and GmWRKY106) particularly under 50 μM L−1 ZnONPs + 10 μM L−1 SeNPs (T8) compared to both negative (T1) and positive control (T2). More importantly, application of nanoparticles, both either independently or in tandem, decreased the expression of GmPT1, GmPT2, GmPT3, GmPT4 and GmPT8 with an exception of GmPT2 under SeNPs treatment group. Thus, the concurrent application of ZnONPs + SeNPs can be considered as eco-friendly fertilizer that will mimic As(V) toxicity and improve the growth and yield of soybean plants in As polluted areas.