Comparison of proteome response to saline and zinc stress in lettuce

How plants respond to heavy metal contamination: a narrative review of proteomic studies and phytoremediation applications

MAIN CONCLUSION

Heavy metal pollution caused by human activities is a serious threat to the environment and human health. Plants have evolved sophisticated defence systems to deal with heavy metal stress, with proteins and enzymes serving as critical intercepting agents for heavy metal toxicity reduction. Proteomics continues to be effective in identifying markers associated with stress response and metabolic processes. This review explores the complex interactions between heavy metal pollution and plant physiology, with an emphasis on proteomic and biotechnological perspectives. Over the last century, accelerated industrialization, agriculture activities, energy production, and urbanization have established a constant need for natural resources, resulting in environmental degradation. The widespread buildup of heavy metals in ecosystems as a result of human activity is especially concerning. Although some heavy metals are required by organisms in trace amounts, high concentrations pose serious risks to the ecosystem and human health. As immobile organisms, plants are directly exposed to heavy metal contamination, prompting the development of robust defence mechanisms. Proteomics has been used to understand how plants react to heavy metal stress. The development of proteomic techniques offers promising opportunities to improve plant tolerance to toxicity from heavy metals. Additionally, there is substantial scope for phytoremediation, a sustainable method that uses plants to extract, sequester, or eliminate contaminants in the context of changes in protein expression and total protein behaviour. Changes in proteins and enzymatic activities have been highlighted to illuminate the complex effects of heavy metal pollution on plant metabolism, and how proteomic research has revealed the plant's ability to mitigate heavy metal toxicity by intercepting vital nutrients, organic substances, and/or microorganisms.

Copper exposure leads to changes in chlorophyll content and secondary metabolite profile in Lantana fucata leaves

Cultivation of plants in environments polluted by metals at toxic levels can affect the biosynthesis of secondary metabolites. Here, we analysed the effect caused by excess copper on the concentration of chlorophylls a and b and the profile of secondary metabolites of Lantana fucata leaves. Five copper (Cu) treatments (mg Cukg-1 soil) were tested: T0, 0; T1, 210; T2, 420; T3, 630; and T4, 840. We found that the concentrations of chlorophylls in the plants decreased when compared to the control. However, this did not lead to a significant reduction in its growth, possibly due to the low translocation of the metal to shoots and the activation of plant defence systems to tolerate the environment in which they are exposed, increasing the emission of lateral roots and activating pathways for the production of secondary metabolites. Therefore, we found a decrease in the concentration of two key compounds in secondary metabolism, p -coumaric and cinnamic acids in treatments with higher copper concentrations. We also found an increase in phenolics. Decreases in p -coumaric and cinnamic acids may have occurred because these are precursors in the synthesis of phenolic compounds, which are increased in the high Cu treatments. Six secondary metabolites were characterised, described for the first time for this plant species. Thus, the presence of excess Cu in the soil may have triggered an increase in the amount of reactive oxygen species in the plants, which that led to the synthesis of antioxidant compounds, as a defence strategy.

Foliar Application of Different Iron Sources Improves Morpho-Physiological Traits and Nutritional Quality of Broad Bean Grown in Sandy Soil

Nano-fertilizers are a new tool that can be used to address plant production challenges, and it addresses such nutrient deficiencies through smart agriculture approaches. Iron (Fe) is a vital element for several metabolic and physiological processes; however, Fe deficiency is common in poorly fertile soils (sand soil) and in arid areas. Therefore, additional research is required to select the most efficient form of iron absorbance. This research was implemented on broad bean plants (Vicia faba L. var. major Harz) to examine the impact of three iron sources: nano-iron (FeNPs, T1), iron sulfate (T2), and chelated iron (T3) as a foliar spray on the morphological properties, physiological attributes, and nutritional status of these plants compared to the untreated plants (control). The obtained results showed that foliar spraying with FeNPs, chelated iron and sulphate iron fertilizers increased plant height by 35.01%, 26.2, and 20.4%; leaf area by 38.8%, 18.3%, and 8.1%; the fresh weight of the plant by 47%, 32.8%, and 7.3%; the dry weight of the plant by 52.9%, 37.3%, and 11.2%; and the number of branches by 47%, 31.3%, and 25.6 %, respectively, compared to the control treatment (CT). Furthermore, the application of FeNPs, chelated iron, and sulphate iron fertilizers improved the number of pods by 47.9%, 24.8%, and 6.1%; the number of seeds by 32.8%, 7.9%, and 2.8%; and seed weight by 20.8%, 9.1%, and 5.4%, compared to control treatment (CT). Additionally, foliar application of FeNPs showed the highest values of photosynthesis rate (Pn), water-use efficiency (WUE), total chlorophyll, and phytohormones (IAA, GA3) compared to all the other treatments. The anatomical structure revealed an enhancement of leaf size and thickness (epidermis cells and mesophyll tissue) affected by FeNPs treatment compared to other treatments. Foliar application of FeNPs also improved the total content of carbohydrates, crude protein, element content (N, P, K, Ca, Na, Fe, Zn, Mn, and Cu), and some amino acids such as lysine, arginine, phenylalanine, isoleucine, and tyrosine in the seeds of broad beans. Based on the above results, the maximum values of all tested measurements were observed when FeNPs were used as the foliar spraying followed by chelated and sulphate iron fertilizers. Therefore, these findings suggest that using FeNPs, as a foliar treatment, could be a promising strategy for reducing the Fe deficiency in sandy soil and enhancing plant growth, pod yield, and pod quality of broad bean plants in addition to being environmentally favored in arid areas.

Proteomic and Genomic Studies of Micronutrient Deficiency and Toxicity in Plants

Micronutrients are essential for plants. Their growth, productivity and reproduction are directly influenced by the supply of micronutrients. Currently, there are eight trace elements considered to be essential for higher plants: Fe, Zn, Mn, Cu, Ni, B, Mo, and Cl. Possibly, other essential elements could be discovered because of recent advances in nutrient solution culture techniques and in the commercial availability of highly sensitive analytical instrumentation for elemental analysis. Much remains to be learned about the physiology of micronutrient absorption, translocation and deposition in plants, and about the functions they perform in plant growth and development. With the recent advancements in the proteomic and molecular biology tools, researchers have attempted to explore and address some of these questions. In this review, we summarize the current knowledge of micronutrients in plants and the proteomic/genomic approaches used to study plant nutrient deficiency and toxicity.

Biosynthesis, distribution, nutritional and organoleptic properties of bitter compounds in fruit and vegetables

Compounds that confer a bitter taste on fruits and vegetables (FAVs) play crucial roles in both plant defense and health promotion. This review details the current knowledge of the distribution, properties (toxicity, pharmacological effects and receptors) and environmental plant responses relating to the biosynthesis, catabolism and transcriptional regulation of 53 bitter plant metabolites in diverse species of FAVs. Some bitter compounds, such as flavonoids, are common in all plant species and make a minor contribution to bitter flavor, but many are synthesized only in specific taxa. They make major contributions to the bitter taste of the corresponding species and some also have significant pharmacological effects. Levels of bitter metabolites are genetically determined, but various environmental cues can affect their final concentration during preharvest development and postharvest storage processes. Molecular approaches are helping to unravel the mechanisms of biosynthesis and regulation of bitter compounds in diverse crop species. This review not only discusses the theoretical basis for utilizing breeding programs and other agricultural technologies to produce FAVs with improved safety, favorable taste and healthier profiles, but also suggests new directions for the utilization of bitter compounds in FAVs for the development of natural pesticides and health-promoting medicines.

A Genome-Wide Association Study Identifying Single-Nucleotide Polymorphisms for Iron and Zinc Biofortification in a Worldwide Barley Collection

Micronutrient deficiency affects half of the world’s population, mostly in developing countries. Severe health issues such as anemia and inadequate growth in children below five years of age and pregnant women have been linked to mineral deficiencies (mostly zinc and iron). Improving the mineral content in staple crops, also known as mineral biofortification, remains the best approach to address mineral malnutrition. Barley is a staple crop in some parts of the world and is a healthy choice since it contains β-glucan, a high dietary protein. Barley mineral biofortification, especially with zinc and iron, can be beneficial since barley easily adapts to marginalized areas and requires less input than other frequently consumed cereals. In this study, we analyzed zinc and iron content in 496 barley samples. The samples were genotyped with an Illumina 50 K SNP chip. Genome-wide association studies (GWAS) identified 62 SNPs and 68 SNPs (p < 0.001) associated with iron and zinc content in grains, respectively. After a Bonferroni correction (p < 0.005), there were 12 SNPs (single-nucleotide polymorphism) associated with Zn and 6 for iron. SNP annotations revealed proteins involved in membrane transport, Zn and Fe binding, linked to nutrient remobilization in grains. These results can be used to develop biofortified barley via marker-assisted selection (MAS), which could alleviate mineral malnutrition.

Stress response of lettuce (Lactuca sativa) to environmental contamination with selected pharmaceuticals: A proteomic study

Pharmaceutical compounds have been found in rivers and treated wastewaters. They often contaminate irrigation waters and consequently accumulate in edible vegetables, causing changes in plants metabolism. The main objective of this work is to understand how lettuce plants cope with the contamination from three selected pharmaceuticals using a label free proteomic analysis. A lettuce hydroponic culture, grown for 36 days, was exposed to metformin, acetaminophen and carbamazepine (at 1 mg/L), during 8 days, after which roots and leaves were sampled and analysed using a liquid chromatography-mass spectrometry proteomics-based approach. In roots, a total of 612 proteins showed differentially accumulation while in leaves 237 proteins were identified with significant differences over controls. Carbamazepine was the contaminant that most affected protein abundance in roots, while in leaves the highest number of differentially accumulated proteins was observed for acetaminophen. In roots under carbamazepine, stress related protein species such as catalase, superoxide dismutase and peroxidases presented higher abundance. Ascorbate peroxidase increased in roots under metformin. Cell respiration protein species were affected by the presence of the three pharmaceuticals suggesting possible dysregulation of the Krebs cycle. Acetaminophen caused the main differences in respiration pathways, with more emphasis in leaves. Lettuce plants revealed different tolerance levels when contaminants were compared, being more tolerant to metformin presence and less tolerant to carbamazepine. SIGNIFICANCE: The significant increase of emerging contaminants in ecosystems makes essential to understand how these compounds may affect the metabolism of different organisms. Our study contributes with a detailed approach of the main interactions that may occur in plant metabolism when subjected to the stress induced by three different pharmaceuticals (acetaminophen, carbamazepine and metformin).

Exogenous application of ZnO nanoparticles and ZnSO4 distinctly influence the metabolic response in Phaseolus vulgaris L

Nanomaterials-mediated contamination (including the highly reactive metal oxides ZnO nanoparticles) is becoming one of the most concerning issues worldwide. In this study, the toxic effects of two chemical species of Zn (ZnO nanoparticles and bulk ZnSO₄) were investigated in bean plants, following either foliar or soil application, at concentrations from 250 to 2000 mg L^-1 using biochemical assays, proteomics and metabolomics. The accumulation of Zn in plant tissues depended on the application type, zinc chemical form and concentration, in turn triggering distinctive morphological, physiological, and redox responses. Bean plants were more sensitive to the foliar than to the soil application, and high concentrations of ZnO NP and bulk ZnSO₄ determined the highest plant growth inhibition and stress symptoms. However, low dosages of ZnSO₄ induced a slight plant growth promotion and better physiological and antioxidative response. Low concentration of Zn leaded to increased activity of stress-related proteins and secondary metabolites with antioxidant capacity, while increasing concentration reached the exhausted phase of the plant stress response, reducing the antioxidant defense system. Such high concentrations increased lipids peroxidation, protein degradation and membranes integrity. Oxidative damage occurred at high concentrations of both chemical species of Zn. Foliar spraying impaired photosynthetic efficiency, while soil applications (especially ZnSO₄) elicited antioxidant metabolites and proteins, and impaired chloroplast-related proteins involved in the electron transport chain and ATP production. Taken together, the results highlighted distinctive and nanoparticles-related toxic effects of ZnO in bean, compared to ionic forms of Zn.

Zinc toxicity in plants: a review

This review highlights the most recent updated information available about Zn phytotoxicity at physiological, biochemical and molecular levels, uptake mechanisms as well as excess Zn homeostasis in plants. Zinc (Zn) is a natural component of soil in terrestrial environments and is a vital element for plant growth, as it performs imperative functions in numerous metabolic pathways. However, potentially noxious levels of Zn in soils can result in various alterations in plants like reduced growth, photosynthetic and respiratory rate, imbalanced mineral nutrition and enhanced generation of reactive oxygen species. Zn enters into soils through various sources, such as weathering of rocks, forest fires, volcanoes, mining and smelting activities, manure, sewage sludge and phosphatic fertilizers. The rising alarm in environmental facet, as well as, the narrow gap between Zn essentiality and toxicity in plants has drawn the attention of the scientific community to its effects on plants and crucial role in agricultural sustainability. Hence, this review focuses on the most recent updates about various physiological and biochemical functions perturbed by high levels of Zn, its mechanisms of uptake and transport as well as molecular aspects of surplus Zn homeostasis in plants. Moreover, this review attempts to understand the mechanisms of Zn toxicity in plants and to present novel perspectives intended to drive future investigations on the topic. The findings will further throw light on various mechanisms adopted by plants to cope with Zn stress which will be of great significance to breeders for enhancing tolerance to Zn contamination.

Promotion of Zinc Tolerance, Acquisition and Translocation of Phosphorus in Mimosa pudica L. Mediated by Arbuscular Mycorrhizal Fungi

Heavy metal contamination of soil is of increasing concern because of its potential risk to human health. In this study, two AMFs (Rhizophagus intraradices and Funneliformis mosseae) substantially increased the biomass of bashfulgrass in Zn-contaminated soil, even at Zn levels of up to 600 mg kg^-1. Zn uptake in R. intraradices- and F. mosseae-mycorrhizal bashfulgrass was increased by 40-fold and 7-fold, respectively, when plants grown in Zn-contaminated (400 mg kg^-1) soil. Elemental analysis showed that neither AMF had an effect on Zn concentration in plant tissues, including the roots and shoots. However, a significant increase of phosphorus (P) concentration was observed, suggesting the increased is from the improved use efficiency of soil nutrients by AMFs. Comparing the two AMFs, better growth performance with more biomass occurred with R. intraradices-inoculated bashfulgrass in Zn-contaminated soil. This is consistent with R. intraradices being more tolerant to Zn than F. mosseae, indicated by a higher colonization percentage in bashfulgrass roots. Taken together, our data indicate that AMFs possibly improve acquisition and translocation of P to promote increased biomass. Moreover, mycorrhiza did not enhance Zn accumulation in shoots and roots of bashfulgrass at the same Zn level. In the future, developing AMF (especially R. intraradices) inoculation of plants might be a desirable means of safe production of ornamental plants in metal-polluted soil.

Leaf proteome modulation and cytological features of seagrass Cymodocea nodosa in response to long-term high CO2 exposure in volcanic vents

Seagrass Cymodocea nodosa was sampled off the Vulcano island, in the vicinity of a submarine volcanic vent. Leaf samples were collected from plants growing in a naturally acidified site, influenced by the long-term exposure to high CO₂ emissions, and compared with others collected in a nearby meadow living at normal pCO₂ conditions. The differential accumulated proteins in leaves growing in the two contrasting pCO₂ environments was investigated. Acidified leaf tissues had less total protein content and the semi-quantitative proteomic comparison revealed a strong general depletion of proteins belonging to the carbon metabolism and protein metabolism. A very large accumulation of proteins related to the cell respiration and to light harvesting process was found in acidified leaves in comparison with those growing in the normal pCO₂ site. The metabolic pathways linked to cytoskeleton turnover also seemed affected by the acidified condition, since a strong reduction in the concentration of cytoskeleton structural proteins was found in comparison with the normal pCO₂ leaves. Results coming from the comparative proteomics were validated by the histological and cytological measurements, suggesting that the long lasting exposure and acclimation of C. nodosa to the vents involved phenotypic adjustments that can offer physiological and structural tools to survive the suboptimal conditions at the vents vicinity.

Proteomics Analysis Indicates Greater Abundance of Proteins Involved in Major Metabolic Pathways in Lactuca sativa cv. Salinas than Lactuca serriola Accession US96UC23

Lettuce (Lactuca sativa), cultivated mainly for its edible leaves and stems, is an important vegetable crop worldwide. Genomes of cultivated lettuce (L. sativa cv. Salinas) and its wild relative L. serriola accession US96UC23 are sequenced, but a clear understanding of the genetic basis for divergence in phenotypes of the two species is lacking. Tandem mass tag (TMT) based mass spectrometry is used to quantitatively compare protein levels between these two species. Four-day old seedlings is transplanted into 500 mL pots filled with soil. Plants are grown for 8 weeks under 250 µmol m-2 sec-1 continuous light, 20 °C and relative humidity between 50-70%. Leaf discs (1 cm diameter) from three individuals per biological replicate are analyzed. A total of 3000 proteins are identified, of which the levels of 650 are significantly different between 'Salinas' and US96UC23. Pathway analysis indicated a higher flux of carbon in 'Salinas' than US96UC23. Many essential metabolic pathways such as tetrapyrrole metabolism and fatty acid biosynthesis are upregulated in 'Salinas' compared with US96UC23. This study provides a reference proteome for researchers interested in understanding lettuce biology and improving traits for cultivation.

Very-long-chain fatty acids (VLCFAs) in plant response to stress

Plant growth is affected by various stresses leading to changes in metabolism. Stress conditions include a variety of biotic and abiotic factors such as pathogens, drought, high and low temperatures and heavy metals. Among multiple physiological responses to stress, there is an adaptive modification in membrane lipid constituents. In particular, the composition of membrane very-long-chain fatty acids (VLCFAs) changes both qualitatively and quantitatively. Here, we evaluate the current data on the effects of stress on plant VLCFAs composition. In summary, some stress conditions lead to an increase of the total amount of saturated and, in certain cases, unsaturated VLCFAs. Currently, it is not completely clear how these molecules participate in the biology of plant cell membranes. Their possible functional roles are discussed.

Cadmium-zinc cross-talk delineates toxicity tolerance in rice via differential genes expression and physiological / ultrastructural adjustments

Understanding the physiological and molecular response of crop genotypes could be useful in eco-toxicological evaluation with cadmium (Cd) and could be a strategy to solve heavy metal contamination in agriculture. This study corroborates unique patterns of Cd accumulation and molecular mechanisms adopted by plants to acquire Cd tolerance and counteractive effects of zinc (Zn) against Cd toxicity. Two rice (Oryza sativa) genotypes (Heizhan 43 and Yinni 801) differing in cadmium tolerance and its accumulation in plant tissues were investigated hydroponically using two Cd levels [Cd₁₀ (10 μM L^-1) and Cd₁₅ (15 μM L^-1)] and two Zn levels [Zn₂₅ (25 μM L^-2) and Zn₅₀ (50 μM L^-1)] and their combinations. Cadmium toxicity rendered substantial reduction in plant height, biomass, chlorophyll contents and photosynthesis as compared to the control plants after 15 days of treatment. Supplementation of Zn evidently ameliorated Cd toxicity by minimizing the reduction in plant growth, chlorophyll contents and photosynthetic attributes (Pn, gs, Ci, and Tr). Comparatively, lower accumulation of Cd in Yinni 801 under combined treatments revealed a preferential uptake of Zn in this genotype. A cross-talk among Cd, Zn, Fe, Ca and K correlated with fluctuating gs, Ci and Tr. Both genotypes also differed in morphological alterations of cell membrane, chloroplasts and appearance of enlarged plastoglobuli along with distorted mitochondria. An increased ascorbate peroxidase activity in roots of Yinni 801 presented a defensive strategy. Relative expression of Cd and Zn ion transporter genes also confirmed the genotypic background of phenotypic divergence. The OsLCT1 and OsHMA2 expression was significant in Heizhan 43, indicating possible translocation of Cd from shoot to grains contrary to Yinni 801, which accumulated Cd in shoot and showed stunted growth. Zn supplementation promises tolerance to Cd in Yinni 801 by differential expression of putative genes for Cd translocation with minimum ultrastructural modifications by maintaining physiological functions in contrast to Heizhan 43.

Proteomics Revealed Distinct Responses to Salinity between the Halophytes Suaeda maritima (L.) Dumort and Salicornia brachiata (Roxb)

Plant resistance to salinity stress is one of the main challenges of agriculture. The comprehension of the molecular and cellular mechanisms involved in plant tolerance to salinity can help to contrast crop losses due to high salt conditions in soil. In this study, Salicornia brachiata and Suaeda maritima, two plants with capacity to adapt to high salinity levels, were investigated at proteome level to highlight the key processes involved in their tolerance to NaCl. With this purpose, plants were treated with 200 mM NaCl as optimal concentration and 500 mM NaCl as a moderate stressing concentration for 14 days. Indeed, 200 mM NaCl did not result in an evident stress condition for both species, although photosynthesis was affected (with a general up accumulation of photosynthesis-related proteins in S. brachiata under salinity). Our findings indicate a coordinated response to salinity in both the halophytes considered, under NaCl conditions. In addition to photosynthesis, heat shock proteins and peroxidase, expansins, signaling processes, and modulation of transcription/translation were affected by salinity. Interestingly, our results suggested distinct mechanisms of tolerance to salinity between the two species considered, with S. brachiata likely having a more efficient mechanism of response to NaCl.

S-Nitrosothiol Signaling Is involved in Regulating Hydrogen Peroxide Metabolism of Zinc-Stressed Arabidopsis

Accumulation of heavy metals such as zinc (Zn) disturbs the metabolism of reactive oxygen (e.g. hydrogen peroxide, H2O2) and nitrogen species (e.g. nitric oxide, NO; S-nitrosoglutathione, GSNO) in plant cells; however, their signal interactions are not well understood. Therefore, this study examines the interplay between H2O2 metabolism and GSNO signaling in Arabidopsis. Comparing the Zn tolerance of the wild type (WT), GSNO reductase (GSNOR) overexpressor 35S::FLAG-GSNOR1 and GSNOR-deficient gsnor1-3, we observed relative Zn tolerance of gsnor1-3, which was not accompanied by altered Zn accumulation capacity. Moreover, in gsnor1-3 plants Zn did not induce NO/S-nitrosothiol (SNO) signaling, possibly due to the enhanced activity of NADPH-dependent thioredoxin reductase. In WT and 35S::FLAG-GSNOR1, GSNOR was inactivated by Zn, and Zn-induced H2O2 is directly involved in the GSNOR activity loss. In WT seedlings, Zn resulted in a slight intensification of protein nitration detected by Western blot and protein S-nitrosation observed by resin-assisted capture of SNO proteins (RSNO-RAC). LC-MS/MS analyses indicate that Zn induces the S-nitrosation of ascorbate peroxidase 1. Our data collectively show that Zn-induced H2O2 may influence its own level, which involves GSNOR inactivation-triggered SNO signaling. These data provide new evidence for the interplay between H2O2 and SNO signaling in Arabidopsis plants affected by metal stress.

Root Hair Single Cell Type Specific Profiles of Gene Expression and Alternative Polyadenylation Under Cadmium Stress

Transcriptional networks are tightly controlled in plant development and stress responses. Alternative polyadenylation (APA) has been found to regulate gene expression under abiotic stress by increasing the heterogeneity at mRNA 3'-ends. Heavy metals like cadmium pollute water and soil due to mining and industry applications. Understanding how plants cope with heavy metal stress remains an interesting question. The Arabidopsis root hair was chosen as a single cell model to investigate the functional role of APA in cadmium stress response. Primary root growth inhibition and defective root hair morphotypes were observed. Poly(A) tag (PAT) libraries from single cell types, i.e., root hair cells, non-hair epidermal cells, and whole root tip under cadmium stress were prepared and sequenced. Interestingly, a root hair cell type-specific gene expression under short term cadmium exposure, but not related to the prolonged treatment, was detected. Differentially expressed poly(A) sites were identified, which largely contributed to altered gene expression, and enriched in pentose and glucuronate interconversion pathways as well as phenylpropanoid biosynthesis pathways. Numerous genes with poly(A) site switching were found, particularly for functions in cell wall modification, root epidermal differentiation, and root hair tip growth. Our findings suggest that APA plays a functional role as a potential stress modulator in root hair cells under cadmium treatment.

Quantitative, Label-Free Proteomics in the Symptomatic Niemann-Pick, Type C1 Mouse Model Using Standard Flow Liquid Chromatography and Thermal Focusing Electrospray Ionization

Niemann-Pick disease, type C1 (NPC1) is a fatal, autosomal recessive, neurodegenerative disorder caused by mutations in the NPC1 gene. As a result, there is accumulation of unesterified cholesterol and sphingolipids in the late endosomal/lysosomal system. This abnormal accumulation results in a cascade of pathophysiological events including progressive, cerebellar neurodegeneration, among others. While significant progress has been made to better understand NPC1, the downstream effects of cholesterol storage and the major mechanisms that drive neurodegeneration remain unclear. In the current study, a) the use of a commercial, highly efficient standard flow-ESI platform for protein biomarker identification is implemented and b) protein biomarkers are identified and evaluated at a terminal time point in the NPC1 null mouse model. In this study, alterations are observed in proteins related to fatty acid homeostasis, calcium binding and regulation, lysosomal regulation, and inositol biosynthesis and metabolism, as well as signaling by Rho family GTPases. New observations from this study include altered expression of Pcp2 and Limp2 in Npc1 mutant mice relative to control, with Pcp2 exhibiting multiple isoforms and specific to the cerebella. This study provides valuable insight into pathways altered in the late-stage pathophysiology of NPC1.

Fractal based complexity analysis of wheat root system under different heavy metals

In this study, fractal geometry was applied to characterize the complexity of the root system morphology of wheat plants under the exposure of heavy metals, namely cadmium (Cd), copper (Cu) and zinc (Zn). We proposed a measure called, relative complexity index (RCI), a ratio based on fractal dimension (FD) before and after exposure to heavy metals. FDs were calculated by box-counting method with digitized and skeletonized images of roots of wheat plants cultivated in hydroculture system. RCI, and relative weight were mesuared under different concentrations of Cd (0.001, 0.01 and 0.05 mM), Cu (0.016, 0.4 and 1.2 mM) and Zn (0.3 and 0.75 mM). Results showed significant reduction of RCI for Cd stress with 0.01 and 0.05, all Cu concentrations and promotion at all zinc concentrations. In comparison, no statistically significant changes were found in conventional relative weight measurement at low concentrations of Cu, Cd and Zn. RCI were more sensitive and were reliable in reflecting the influence of heavy metals than the conventional measure. These results imply that RCI can be an effective measure of the negative and positive effects of heavy metals on the development of complexity of root system under heavy metal exposures.

Smelling the metal: Volatile organic compound emission under Zn excess in the mint Tetradenia riparia

This work investigated the effect of Zn excess on growth, metal accumulation and photosynthetic changes in Tetradenia riparia, in relation to possible variations in the composition of the plant volatilome. Experiments were carried out in hydroponics exposing plants to a range of Zn concentrations. Zinc excess negatively affected plant growth in a dose-dependent manner. The metal was accumulated proportionally to its concentration in the medium and preferentially allocated to roots. All the photosynthetic parameters and the concentration of some photosynthetic pigments were negatively affected by Zn, whereas the level of leaf total soluble sugars remained unchanged. Twenty-three different VOCs were identified in the plant volatilome. Each compound was emitted at a different level and intensity of emission was manifold increased by the presence of Zn in the growth medium. The Zn-induced compounds could represent both an adaptive response (f.i. methanol, acetylene, C₆-aldehydes, isoprene, terpenes) and a damage by-product (f.i. propanal, acetaldehyde, alkyl fragments) of the metal presence in the culture medium. Given that the Zn-mediated induction of those VOCs, considered protective, occurred even under a Zn-limited photosynthetic capacity, our work supports the hypothesis of an active role of such molecules in an adaptive plant response to trace metal stress.

Combining micro-RNA and protein sequencing to detect robust biomarkers for Graves' disease and orbitopathy

Graves’ Disease (GD) is an autoimmune condition in which thyroid-stimulating antibodies (TRAB) mimic thyroid-stimulating hormone function causing hyperthyroidism. 5% of GD patients develop inflammatory Graves’ orbitopathy (GO) characterized by proptosis and attendant sight problems. A major challenge is to identify which GD patients are most likely to develop GO and has relied on TRAB measurement. We screened sera/plasma from 14 GD, 19 GO and 13 healthy controls using high-throughput proteomics and miRNA sequencing (Illumina’s HiSeq2000 and Agilent-6550 Funnel quadrupole-time-of-flight mass spectrometry) to identify potential biomarkers for diagnosis or prognosis evaluation. Euclidean distances and differential expression (DE) based on miRNA and protein quantification were analysed by multidimensional scaling (MDS) and multinomial regression respectively. We detected 3025 miRNAs and 1886 proteins and MDS revealed good separation of the 3 groups. Biomarkers were identified by combined DE and Lasso-penalized predictive models; accuracy of predictions was 0.86 (±0:18), and 5 miRNA and 20 proteins were found including Zonulin, Alpha-2 macroglobulin, Beta-2 glycoprotein 1 and Fibronectin. Functional analysis identified relevant metabolic pathways, including hippo signaling, bacterial invasion of epithelial cells and mRNA surveillance. Proteomic and miRNA analyses, combined with robust bioinformatics, identified circulating biomarkers applicable to diagnose GD, predict GO disease status and optimize patient management.

Morphological, proteomic and metabolomic insight into the effect of cerium dioxide nanoparticles to Phaseolus vulgaris L. under soil or foliar application

Chemically synthesized nanoparticles (NPs) are widely used in industry and concern over their impact on the environment is rising. In this study, greenhouse grown bean (Phaseolus vulgaris L.) plants were treated with CeO₂ NPs suspensions at 0, 250, 500, 1000, and 2000mgL^-1 either aerially by spraying or via soil application. At 15days after treatment, plants were analyzed for Ce uptake, morphological and biochemical assays, as well as high-resolution mass spectrometry based metabolomics and proteomics. The results from ICP-MS assays showed a dose dependent absorption, uptake and translocation of Ce through both roots and leaves; Ce content increased from 0.68 up to 1894mgkg^-1 following spray application, while concentrations were three orders lower following soil application (0.59 to 2.19mgkg^-1). Electrolyte leakage increased with NPs rate, from 25.2% to 70.3% and from 24.8% to 32.9% following spray and soil application, respectively. Spraying lowered stomatal density (from 337 to 113 per mm²) and increased stomatal length (from 12.8 to 19.4μm), and altered photosynthesis and electron transport chain biochemical machinery. The increase in Ce content induced accumulation of osmolites (proline increased from 0.54 to 0.65mg/g under spray application), phytosiderophores (muconate and mugineate compounds showed increase fold-changes >16) and proteins involved in folding or turnover. NPs application induced membrane damage, as evidenced by the increase in membrane lipids degradates and by the increase in electrolyte leakage, and caused oxidative stress. Most of the responses were not linear but dose-dependent, whereas metabolic disruption is expected at the highest NPs dosage. Both proteomics and metabolomics highlighted a stronger effect of CeO₂ NPs spraying, as compared to soil application. High concentrations of NPs in the environment have been confirmed to pose toxicity concern towards plants, although important differences could be highlighted between aerial deposition and soil contamination.

Proteomic and genomic responses of plants to nutritional stress

Minerals or trace elements in small amount are essential nutrients for every plant, but when the internal concentration exceeds the threshold, these essential elements do create phytotoxicity. Plant responses to elemental stresses are very common due to different anthropogenic activities; however it is a complex phenomenon with individual characteristics for various species. To cope up with the situation, a plant produces a group of strategies both in proteomic and genomic level to overcome it. Controlling the metal stress is known to activate a multigene response resulting in the changes in various proteins, which directly affects almost all biological processes in a living cell. Therefore, proteomic and genomic approaches can be useful for elucidating the molecular responses under metal stress. For this, it is tried to provide the latest knowledge and techniques used in proteomic and genomic study during nutritional stress and is represented here in review form.

Lettuce facing microcystins-rich irrigation water at different developmental stages: Effects on plant performance and microcystins bioaccumulation

This study investigated the microcystins (MCs)-rich irrigation water effect on lettuce of different developmental stages, i.e. during a two months period, covering the whole period from seed germination to harvest at marketable size of the plant. We followed four lettuce plant groups receiving MCs-rich water (1.81μgl-1 of dissolved MCs), originating from the Karla Reservoir, central Greece: 1) from seeds, 2) the cotyledon, 3) two true leaves and 4) four true leaves stages, all of which were compared to control plants that received tap water. Lettuce growth, photosynthetic performance, biochemical and mineral characteristics, as well as MCs accumulation in leaves, roots and soil were measured. The overall performance of lettuce at various developmental stages pointed to increased tolerance since growth showed minor alterations and non-enzymatic antioxidants remained unaffected. Plants receiving MCs-rich water from the seed stage exhibited higher photosynthetic capacity, chlorophylls and leaf nitrogen content. Nevertheless, considerable MCs accumulation in various plant tissues occurred. The earlier in their development lettuce plants started receiving MCs-rich water, the more MCs they accumulated: roots and leaves of plants exposed to MCs-rich water from seeds and cotyledons stage exhibited doubled MCs concentrations compared to respective tissues of the 4 Leaves group. Furthermore, roots accumulated significantly higher MCs amounts than leaves of the same plant group. Concerning human health risk, the Estimated Daily Intake values (EDI) of Seed and Cotyledon groups leaves exceeded Tolerable Daily Intake (TDI) by a factor of 6, while 2 Leaves and 4 Leaves groups exceeded TDI by a factor of 4.4 and 2.4 respectively. Our results indicate that irrigation of lettuce with MCs-rich water may constitute a serious public health risk, especially when contaminated water is received from the very early developmental stages (seed and cotyledon). Finally, results obtained for the tolerant lettuce indicate that MCs bioaccumulation in edible tissues is not necessarily coupled with phytotoxic effects.

Effect of Different Elicitors and Preharvest Day Application on the Content of Phytochemicals and Antioxidant Activity of Butterhead Lettuce (Lactuca sativa var. capitata) Produced under Hydroponic Conditions

The effect of four elicitors on phytochemical content in two varieties of lettuce was evaluated. The best preharvest day for application of each elicitor was chosen. Solutions of arachidonic acid (AA), salicylic acid (SA), methyl jasmonate (MJ), and Harpin protein (HP) were applied by foliar aspersion on lettuce leaves while cultivating under hydroponic conditions. Application of elicitors was done at 15, 7, 5, 3, or 1 day before harvest. Green lettuce showed the highest increase in phytochemical content when elicitors (AA, SA, and HP) were applied on day 7 before harvest. Similarly, antioxidant activity rose in all treatments on day 7. In red lettuce, the highest content of bioactive molecules occurred in samples treated on day 15. AA, SA, and HP were the elicitors with the highest effect on phytochemical content for both varieties, mainly on polyphenol content. Antioxidant activity also increased in response to elicitation. HPLC-MS showed an increase in the content of phenolic acids in green and red lettuce, especially after elicitation with SA, suggesting activation of the caffeic acid pathway due to elicitation.

Proteomic insight into the mitigation of wheat root drought stress by arbuscular mycorrhizae

Arbuscular mycorrhizal fungi (AMF) are plant growth promoters that ameliorate plant-water relations and the nutrient uptake of wheat. In this work, two cultivars of Triticum spp., a bread and a durum wheat, grown under drought stress and inoculated or not by AMF, are evaluated through a shotgun proteomic approach. The AMF association had beneficial effects as compared to non-mycorrhizal roots, in both bread and durum wheat. The beneficial symbiosis was confirmed by measuring morphological and physiological traits. In our work, we identified 50 statistically differential proteins in the bread wheat cultivar and 66 differential proteins in the durum wheat cultivar. The findings highlighted a modulation of proteins related to sugar metabolism, cell wall rearrangement, cytoskeletal organization and sulphur-containing proteins, as well as proteins related to plant stress responses. Among differentially expressed proteins both cultivars evidenced a decrease in sucrose:fructan 6-fructosyltransferas. In durum wheat oxylipin signalling pathway was involved with two proteins: increased 12-oxo-phytodienoic acid reductase and decreased jasmonate-induced protein, both related to the biosynthesis of jasmonic acid. Interactome analysis highlighted the possible involvement of ubiquitin although not evidenced among differentially expressed proteins. The AMF association helps wheat roots reducing the osmotic stress and maintaining cellular integrity.

BIOLOGICAL SIGNIFICANCE

Drought is one of the major constraints that plants must face in some areas of the world, associated to climate change, negatively affecting the worldwide plant productivity. The adoption of innovative agronomic protocols may represent a winning strategy in facing this challenge. The arbuscular mycorrhizal fungi (AMF) inoculation may represent a natural and sustainable way to mitigate the negative effects due to drought in several crop, ameliorating plant growth and development. Studies on the proteomic responses specific to AMF in drought-stressed plants will help clarify how mycorrhization elicits plant growth, nutrient uptake, and stress-tolerance responses. Such studies also offer the potential to find biological markers and genetic targets to be used during breeding for new drought-resistant varieties.

Zinc Excess Triggered Polyamines Accumulation in Lettuce Root Metabolome, As Compared to Osmotic Stress under High Salinity

Abiotic stresses such as salinity and metal contaminations are the major environmental stresses that adversely affect crop productivity worldwide. Crop responses and tolerance to abiotic stress are complex processes for which "-omic" approaches such as metabolomics is giving us a newest view of biological systems. The aim of the current research was to assess metabolic changes in lettuce (Lactuca sativa L.), by specifically probing the root metabolome of plants exposed to elevated isomolar concentrations of NaCl and ZnSO4. Most of the metabolites that were differentially accumulated in roots were identified for stress conditions, however the response was more intense in plants exposed to NaCl. Compounds identified in either NaCl or ZnSO4 conditions were: carbohydrates, phenolics, hormones, glucosinolates, and lipids. Our findings suggest that osmotic stress and the consequent redox imbalance play a major role in determining lettuce root metabolic response. In addition, it was identified that polyamines and polyamine conjugates were triggered as a specific response to ZnSO4. These findings help improve understanding of how plants cope with abiotic stresses. This information can be used to assist decision-making in breeding programs for improving crop tolerance to salinity and heavy metal contaminations.

Responses of Nigella sativa L. to Zinc Excess: Focus on Germination, Growth, Yield and Yield Components, Lipid and Terpene Metabolism, and Total Phenolics and Antioxidant Activities

A comprehensive analysis of the responses of Nigella sativa L. to elevated zinc concentrations was assessed in pot experiments. Zn excess supply did not affect the germination but drastically reduced radicle elongation. A concentration-dependent reduction in all growth parameters, yield, and yield components was observed. With the increasing Zn concentrations, total lipid contents decreased and changes in fatty composition toward the production of saturated ones were underscored. Despite the reduction in the seeds essential oil yield, a redirection of the terpene metabolism toward the synthesis of oxygenated compounds has been evidenced. A significant increase in the total phenols and flavonoids contents concomitant with improved antioxidant activities has also been found. Collectively, these results highlight the possible use of N. sativa L. in phytoremediation applications, on the one hand, and that Zn excess could represent an excellent alternative to improve the nutritional attributes of this important species, on the other hand.

Iron Oxide Nanoparticles as a Potential Iron Fertilizer for Peanut (Arachis hypogaea)

Nanomaterials are used in practically every aspect of modern life, including agriculture. The aim of this study was to evaluate the effectiveness of iron oxide nanoparticles (Fe2O3 NPs) as a fertilizer to replace traditional Fe fertilizers, which have various shortcomings. The effects of the Fe2O3 NPs and a chelated-Fe fertilizer (ethylenediaminetetraacetic acid-Fe; EDTA-Fe) fertilizer on the growth and development of peanut (Arachis hypogaea), a crop that is very sensitive to Fe deficiency, were studied in a pot experiment. The results showed that Fe2O3 NPs increased root length, plant height, biomass, and SPAD values of peanut plants. The Fe2O3 NPs promoted the growth of peanut by regulating phytohormone contents and antioxidant enzyme activity. The Fe contents in peanut plants with Fe2O3 NPs and EDTA-Fe treatments were higher than the control group. We used energy dispersive X-ray spectroscopy (EDS) to quantitatively analyze Fe in the soil. Peanut is usually cultivated in sandy soil, which is readily leached of fertilizers. However, the Fe2O3 NPs adsorbed onto sandy soil and improved the availability of Fe to the plants. Together, these results show that Fe2O3 NPs can replace traditional Fe fertilizers in the cultivation of peanut plants. To the best of our knowledge, this is the first research on the Fe2O3 NPs as the iron fertilizer.