Drilling into the Metabolomics to Enhance Insight on Corn and Wheat Responses to Molybdenum Trioxide Nanoparticles

Abstract

Metabolomics is an emerging tool to understand the potential implications of nanotechnology, particularly for agriculture. Although molybdenum (Mo) is a known plant micronutrient, little is known of its metabolic perturbations. Here, corn and wheat seedlings were exposed to MoO 3 nanoparticles (NPs) and the corresponding bioavailable Mo 6+ ion at moderate and excessive levels through root exposures. Physiologically, corn was more sensitive to Mo, which accumulated up to 3.63 times more Mo than wheat. In contrast, metabolomics indicated 21 dysregulated metabolites in corn leaves and 53 in wheat leaves. Five more metabolomic pathways were perturbed in wheat leaves compared to corn leaves. In addition to the overall metabolomics analysis, we also analyzed individual metabolite classes (e.g., amino acids, organic acids, etc.), yielding additional dysregulated metabolites in plant tissues: 7 for corn and 7 for wheat. Most of these were amino acids as well as some sugars. Additional significantly dysregulated metabolites (e.g., asparagine, fructose, reduced glutathione, mannose) were identified in both corn and wheat, due to Mo NP exposure, by employing individual metabolite group analysis. Targeted metabolite analysis of individual groups is thus important for finding additional significant metabolites. We demonstrate the value of metabolomics to study early stage plant responses to NP exposure.

Metabolomic Response of Early-Stage Wheat (Triticum aestivum) to Surfactant-Aided Foliar Application of Copper Hydroxide and Molybdenum Trioxide Nanoparticles

“…Growth conditions were 150 µmol•m −2 •s −1 light intensity (as daylight white) for 16 h daily, the temperature was set at 22 • C, and relative humidity was 60%. A 10% Hoagland solution was used for watering purposes to ensure adequate nutrients for plant growth [49]. The water content in the pots was maintained between 70 and 90%.…”

“…Then, 8 mL of H 2 O 2 reagent (Thermo Scientific™, Product No. H325-4) was added into the system and held at 115 • C for another 60 min [45,49]. When the digestion process was complete, all samples were diluted to the 50 mL mark for nutrient analysis.…”

“…A total of 82 targeted metabolites (Table S1) were selected from previous studies, which showed good sensitivities during plant (corn, cucumber, soybean, and wheat) exposures to various NMs (Ag, Cd, Cu, and Mo) [49,[59][60][61][62]. Briefly, the freeze-dried plant samples were finely ground by using pestle and mortar with liquid nitrogen.…”

“…Metabolomics is increasingly being employed to study plant molecular responses/ mechanisms to different stimulus (e.g., NMs) [4,[38][39][40][41][42][43][44][45][46][47][48][49][50]. Given the extended use of the commercial nanopesticide Kocide 3000 (active ingredient: Cu(OH) 2 NMs), the effects of Cu(OH) 2 NMs on basil (Ocimum basilicum) [4], cucumber (Cucumis Sativus) [44,46], maize (Zea mays) [44,45], and lettuce (Lactuca Sativa) [47] have been explored.…”

“…Excess exposure to Mo NMs and Mo 6+ can inhibit root growth/elongation, prolong seed germination, increase nitrate reductase, and cause oxidative imbalance [53][54][55][56][57]. Recently we demonstrated that corn and wheat exposed to MoO 3 NMs through a three-week root exposure (at 200 and 1000 mg/kg Mo levels) resulted in a significant response in plant roots and leaves at the molecular level [49]. Although the physiological data showed that the MoO 3 NMs had a more severe impact on corn roots and above-ground plant tissues, 53 dysregulated metabolites were found in wheat leaves compared with 21 in corn leaves.…”