Protein Carbonylation As a Biomarker of Heavy Metal, Cd and Pb, Damage in Paspalum fasciculatum Willd. ex Flüggé

Elemental mercury accumulation in Eichhornia crassipes (Mart.) Solms-Laubach

The aquatic macrophyte Eichhornia crassipes has great potential for the control of Hg pollution in the environment. The aim of this study was to investigate the capability of E. crassipes to accumulate elemental mercury (Hg⁰). The plants were exposed for 30 days to 5, 10, 20, 40, and 80 mg of Hg⁰ in a 1-L Hoagland medium with the Hg⁰ settled at the bottom of the flask. The roots of the plants did not touch the mercury during the treatment. After exposure, the total Hg (T-Hg) concentrations in the roots, leaves, and stems were measured using a direct mercury (Hg) analyzer. The highest concentrations were found at 80 mg Hg⁰ treatment in the roots, leaves, and stems, in that order. The translocation factor indicated a poor capability of Hg to translocate from the roots to the shoots. The relative growth and the root-length inhibition measurements showed that the differences between Hg⁰ treatments were not significant. In addition, the treatments negatively affected the chlorophyll concentration. The carotenoid content was found to be significantly different at 20 and 40 mg of Hg⁰ in 1 L. Regarding the carbonyl index in root proteins, significant differences compared to control were found at the highest Hg treatment. Based on these results, it was shown that E. crassipes is able to take up elemental Hg from Hoagland medium. However, the Hg⁰ treatments did not show a strong stress-response activation mechanism in the evaluated plant tissues.

Proteomic Changes in Paspalum fasciculatum Leaves Exposed to Cd Stress

(1) Background: Cadmium is a toxic heavy metal that is widely distributed in water, soil, and air. It is present in agrochemicals, wastewater, battery waste, and volcanic eruptions. Thus, it can be absorbed by plants and enter the trophic chain. P. fasciculatum is a plant with phytoremediation capacity that can tolerate Cd stress, but changes in its proteome related to this tolerance have not yet been identified. (2) Methods: We conducted a quantitative analysis of the proteins present in P. fasciculatum leaves cultivated under greenhouse conditions in mining soils doped with 0 mg kg−1 (control), 30 mg kg−1, or 50 mg kg−1. This was carried out using the label-free shotgun proteomics technique. In this way, we determined the changes in the proteomes of the leaves of these plants, which allowed us to propose some tolerance mechanisms involved in the response to Cd stress. (3) Results: In total, 329 variable proteins were identified between treatments, which were classified into those associated with carbohydrate and energy metabolism; photosynthesis; structure, transport, and metabolism of proteins; antioxidant stress and defense; RNA and DNA processing; and signal transduction. (4) Conclusions: Based on changes in the differences in the leaf protein profiles between treatments, we hypothesize that some proteins associated with signal transduction (Ras-related protein RABA1e), HSPs (heat shock cognate 70 kDa protein 2), growth (actin-7), and cellular development (actin-1) are part of the tolerance response to Cd stress.

Effects of lead, cadmium and zinc on protein changes in Silene vulgaris shoots cultured in vitro

In the present research, Silene vulgaris as a representative species growing on both unpolluted and heavy metal (HM) polluted terrains were used to identify ecotype-specific responses to metallic stress. Growth, cell ultrastructure and element accumulations were compared between non-metallicolous (NM), calamine (CAL) and serpentine (SER) specimens untreated with HMs and treated with Pb, Cd and Zn ions under in vitro conditions. Moreover, proteins' modifications related to their level, carbonylation and degradations via vacuolar proteases were verified and linked with potential mechanisms to cope with ions toxicity. Our experiment revealed diversified strategy of HM uptake in NM and both metallicolous ecotypes, in which antagonistic relationship of Zn and Pb/Cd ions provided survival benefits for the whole organism. Despite this similarity, growth rate and metabolic pathways induced in CAL and SER shoots varied significantly. Exposition to HMs in CAL culture led to drop in protein level by approximately 16% compared to the control. This parameter nearly correlated with the enhanced activity of proteases at pH 5.2 as well as possible glutamate changes to proline and reduced glutathione, resulting in intensified growth and first signs of cell senescence. In turn, SER shoots were characterized by growth retardation (to 53% of the control), although protein level and carbonylation were not modified, while a deeper insight into protein network showed its remodeling towards production of polyamines and 2-oxoglutarate delivered to the Krebs cycle. Contrary, an uncontrolled HM influx in NM shoots contributed to morpho-structural disorders accompanied by an increase activity of proteases involved in the degradation of oxidized proteins, what pointed to metal-induced autophagy. Taken together, S. vulgaris ecotypes respond to stress by triggering various mechanisms engaged their survival and/or death under HM treatment.

Phytostabilization of Pb-Zn Mine Tailings with Amorpha fruticosa Aided by Organic Amendments and Triple Superphosphate

A greenhouse pot trial was conducted to investigate the effect of organic amendments combined with triple superphosphate on the bioavailability of heavy metals (HMs), Amorpha fruticosa growth and metal uptake from Pb-Zn mine tailings. Cattle manure compost (CMC), spent mushroom compost (SMC) and agricultural field soil (AFS) were applied to tailings at 5%, 10%, 20% and 30% w/w ratio, whereas sewage sludge (SS) and wood biochar (WB) were mixed at 2.5%, 5%, 10% and 20% w/w ratio. Triple superphosphate (TSP) was added to all the treatments at 4:1 (molar ratio). Amendments efficiently decreased DTPA-extracted Pb, Zn, Cd and Cu in treatments. Chlorophyll contents and shoot and root dry biomass significantly (p < 0.05) increased in the treatments of CMC (except T4 for chlorophyll b) and SMC, whereas treatments of SS (except T1 for chlorophyll a and b), WB and AFS (except T4 for chlorophyll a and b) did not show positive effects as compared to CK1. Bioconcentration factor (BCF) and translocation factor (TF) values in plant tissues were below 1 for most treatments. In amended treatments, soluble protein content increased, phenylalanine ammonialyase (PAL) and polyphenol oxidase (PPO) decreased, and catalase (CAT) activity showed varied results as compared to CK1 and CK2. Results suggested that A. fruticosa can be a potential metal phytostabilizer and use of CMC or SMC in combination with TSP are more effective than other combinations for the in situ stabilization of Pb-Zn mine tailings.