Effect of cadmium at concentrations of 1 and 10 μM on biomass increment, mineral nutrient elements (potassium, calcium, and magnesium) accumulation, and oxalic acid pools in organs of Amaranthus...

In recent decades, heavy metal pollution has become a significant environmental stress factor. Plants are characterized by high biochemical plasticity and can adjust their metabolism to ensure survival under a changing environment. Here we report, to our knowledge, the first gas chromatography-mass spectrometry (GC-MS)-based metabolomics study of Zn-induced stress responses in Amaranthus caudatus plants. The study was performed with root and leaf aqueous methanolic extracts after their lyophilization and sequential derivatization with methoxylamine hydrochloride and N-methyl-N-(trimethylsilyl)trifluoroacetamide. In total, 419 derivatives were detected in the samples, and 144 of them could be putatively annotated. The metabolic shifts in seven-week-old A. caudatus plants in response to a seven-day treatment with 300 µmol/L ZnSO₄·7H₂O in nutrient solution were organ-specific and more pronounced in roots. Most of the responsive metabolites were up-regulated and dominated by sugars and sugar acids. The revealed effects could be attributed to the involvement of these metabolites in osmotic regulation, antioxidant protection and Zn²⁺ complexation. A 59-fold up-regulation of gluconic acid in roots distinctly indicated enhanced glucose oxidation due to oxidative stress upon the Zn treatment. Gluconic acid might be further employed in Zn²⁺ complexation. Pronounced Zn-induced up-regulation of salicylic acid in roots and shoots suggested a key role of this hormone in stress signaling and activation of Zn stress tolerance mechanisms. Overall, our study provides the first insight into the general trends of Zn-induced biochemical rearrangements and main adaptive metabolic shifts in A. caudatus.

Because of ongoing climate change, drought is becoming the major factor limiting productivity of all plants, including legumes. As these protein-rich crops form symbiotic associations with rhizobial bacteria — root nodules — they readily lose their productivity under drought conditions. Understanding the underlying molecular mechanisms might give access to new strategies to preserve the productivity of legume crops under dehydration. As was shown recently, development of drought response is accompanied by alterations in the patterns of protein glycation and formation of advanced glycation end products (AGEs) that might be a part of unknown regulatory mechanisms. Therefore, here we address the effects of moderate drought on protein dynamics and AGE patterns in pea (Pisum sativum) root nodules. For this, plants inoculated with rhizobial culture were subjected to osmotic stress for one week, harvested, the total protein fraction was isolated from root nodules by phenol extraction, analyzed by bottom-up LC-MS-based proteomics, and AGE patterns were characterized. Surprisingly, despite the clear drought-related changes in phenotype and stomatal conductivity, only minimal accompanying expressional changes (14 rhizobial and 14 pea proteins, mostly involved in central metabolism and nitrogen fixation) could be observed. However, 71 pea and 97 rhizobial proteins (mostly transcription factors, ABC transporters and effector enzymes) were glycated, with carboxymethylation being the major modification type. Thereby, the numbers of glycated sites in nodule proteins dramatically decreased upon stress application. It might indicate an impact of glycation in regulation of transport, protein degradation, central, lipid and nitrogen metabolism. The data are available at Proteome Xchange (accession: PXD024042). advanced glycation end products (AGEs), drought stress, glycation, pea (Pisum sativum), polyethylene glycol (PEG), proteomics, root nodules

A crucial feature of plant performance is its strong dependence on the availability of essential mineral nutrients, affecting multiple vital functions. Indeed, mineral-nutrient deficiency is one of the major stress factors affecting plant growth and development. Thereby, nitrogen and potassium represent the most abundant mineral contributors, critical for plant survival. While studying plant responses to nutrient deficiency, one should keep in mind that mineral nutrients, along with their specific metabolic roles, are directly involved in maintaining cell ion homeostasis, which relies on a finely tuned equilibrium between cytosolic and vacuolar ion pools. Therefore, in this chapter we briefly summarize the role of the ion homeostasis system in cell responses to environmental deficiency of nitrate and potassium ions. Special attention is paid to the implementation of plant responses via NO3− and K+ root transport and regulation of ion distribution in cell compartments. These responses are strongly dependent on plant species, as well as severity and duration of nutrient deficiency.

Zinc excess (Zn stress) could lead to deleterious effects in plants such as enhanced ROS production, inhibition of photosynthetic machinery, and impairment of nutrient uptake. Hence, we aimed to investigate the complexity of metabolic responses to Zn stress in Amaranthus caudatus young and mature leaves, as well as in roots by means of proteomics. Our previous metabolomics research has indicated potential involvement of gluconate and salicylate in Zn tolerance mechanisms. However, proteomics study of metabolic adjustments underlying Zn stress tolerance can give additional insight to the issue, as a lot of enzymes are known to be affected by the excess of transitional metals. The results obtained through bottom-up proteomics were complementary to our earlier metabolomics data and, furthermore, enlightened other important details in the metabolic response of A. caudatus plants to the applied Zn stress. In particular, the significant involvement of redox-related enzymes was shown, especially for the roots, and their possible interactions with salicylate and jasmonate signaling could be proposed. Furthermore, Zn²⁺-induced changes in roots and young leaves strongly affected sugar metabolism, enhanced protein quality control system, while mature leaves were characterized by remarkable decrease in subunits of photosynthetic electron transport complexes. Thus, this work emphasizes massive metabolic reprogramming aimed to reinforce root defense responses while supporting young leaves with sugar metabolites. Mass spectrometry proteomics data are available via ProteomeXchange with identifier PXD069557.

During the last decades, pollution with heavy metals (HM) became an important stress factor for plants. However, due to their biochemical plasticity, plants can adjust their metabolism to ensure survival under changing environmental conditions. In the most comprehensive and straightforward way these metabolic shifts can be addressed by the untargeted mass spectrometry-based metabolomics approach. However, although this methodology is well-established for cadmium-related responses, comprehensive metabolomics studies of Zn-induced metabolic shifts are still missing. Therefore, here we propose, to the best of our knowledge, the first gas chromatography-mass spectrometry (GC-MS)-based metabolomics study of Zn2+-induced stress responses in amaranth. Thereby, 419 metabolites could be annotated and 144 of them were unambiguously identified. The metabolic shifts were organ-specific and more pronounced in roots. The most of the responsive metabolites were up-regulated and dominated with sugars and, to a lesser extent, TCA-related organic acids (a total of 51 and 41, respectively) that could be attributed to their involvement in osmoregulation, ROS scavenging and complexation of Zn2+ ions. Galactose was the most Zn2+-responsive root sugar that indicated its possible role in Zn2+ ion binding to the root cell walls. A 59-fold increase of gluconate content in roots clearly indicated its involvement in Zn2+ chelation. A high Zn2+–induced up-regulation of salicylic acid in roots and shoots suggested a key role of this hormone in the activation of Zn2+ stress tolerance mechanisms. Thus, our study provides the first insight in the general trends in Zn-induced biochemical rearrangements and main adaptive metabolic shifts in A. caudatus plants.