The subcellular distribution of miRNA isoforms, tRNA-derived fragments, and rRNA-derived fragments depends on nucleotide sequence and cell type.

BACKGROUND: MicroRNA isoforms (isomiRs), tRNA-derived fragments (tRFs), and rRNA-derived fragments (rRFs) represent most of the small non-coding RNAs (sncRNAs) found in cells. Members of these three classes modulate messenger RNA (mRNA) and protein abundance and are dysregulated in diseases. Experimental studies to date have assumed that the subcellular distribution of these molecules is well-understood, independent of cell type, and the same for all isoforms of a sncRNA. RESULTS: We tested these assumptions by investigating the subcellular distribution of isomiRs, tRFs, and rRFs in biological replicates from three cell lines from the same tissue and same-sex donors that model the same cancer subtype. In each cell line, we profiled the isomiRs, tRFs, and rRFs in the nucleus, cytoplasm, whole mitochondrion (MT), mitoplast (MP), and whole cell. Using a rigorous mathematical model we developed, we accounted for cross-fraction contamination and technical errors and adjusted the measured abundances accordingly. Analyses of the adjusted abundances show that isomiRs, tRFs, and rRFs exhibit complex patterns of subcellular distributions. These patterns depend on each sncRNA's exact sequence and the cell type. Even in the same cell line, isoforms of the same sncRNA whose sequences differ by a few nucleotides (nts) can have different subcellular distributions. CONCLUSIONS: SncRNAs with similar sequences have different subcellular distributions within and across cell lines, suggesting that each isoform could have a different function. Future computational and experimental studies of isomiRs, tRFs, and rRFs will need to distinguish among each molecule's various isoforms and account for differences in each isoform's subcellular distribution in the cell line at hand. While the findings add to a growing body of evidence that isomiRs, tRFs, rRFs, tRNAs, and rRNAs follow complex intracellular trafficking rules, further investigation is needed to exclude alternative explanations for the observed subcellular distribution of sncRNAs.

Different stoichiometric ratios of Ca and Cd affect the Cd tolerance of Capsicum annuum L. by regulating the subcellular distribution and chemical forms of Cd.

The effect of calcium (Ca)-cadmium (Cd) interactions on the plant Cd bioaccumulation process may be closely related to the ecological Ca/Cd stoichiometry in the substrate. However, owing to the complexity of plant absorption, accumulation mechanisms and influencing factors, the mechanism of Ca-mediated Cd bioaccumulation and Cd tolerance in Capsicum is still unclear. In this study, the bioaccumulation, subcellular distribution and chemical forms of Cd in Capsicum were analysed via pot experiments to reveal the Ca-mediated Cd bioaccumulation process and its detoxification mechanism under different Ca/Cd stoichiometric ratios. The results revealed that an increase in the substrate Ca/Cd ratio promoted the accumulation of Cd in the roots; restricted the transport of Cd to the stems, leaves and peppers; and promoted the accumulation of Cd in the aboveground leaves but decreased its accumulation in edible parts. Cd was enriched mainly in the cell wall and cell-soluble fraction in each tissue and was enriched in only 1 %-13 % of the organelles. The accumulation of Cd in the cell wall and cell-soluble fractions of roots treated with different Ca concentrations increased by 56.57 %-236.98 % and 64.41 %-442.14 %, respectively. The carboxyl, hydroxyl and amino groups on the root cell wall play important roles in binding and fixing Cd2+. Moreover, the increase in the Ca content also increased the proportion of pectin and protein-bound Cd (F-NaCl), insoluble phosphate-bound Cd (F-C) and insoluble oxalate-bound Cd (F-HCl) in the roots, stems and leaves and reduced the proportion of highly active chemical forms such as inorganic acid salt-bound Cd (F-E) and water-soluble phosphate-bound Cd (F-W). Our study revealed that the bioaccumulation of Cd in Capsicum was influenced by the Ca/Cd ratio and that Ca could alleviate Cd stress by regulating the subcellular distribution and chemical form ratio of Cd in different tissues where the cell wall plays an important role in Cd tolerance and detoxification.

Unveiling the absorption, translocation, and metabolism of penthiopyrad in pakchoi under hydroponic and soil-cultivated conditions.

The efficient use of pesticides has long been a topic of public concern, necessitating a thorough understanding of their movement in plants. This study investigates the translocation and distribution of penthiopyrad in pakchoi plants cultivated both in hydroponic and soil-cultivated conditions. Results indicate that penthiopyrad predominantly accumulates in the roots, with concentrations of 11.3-53.9 mg/kg following root application, and in the leaves, with concentrations of 2.0-17.1 mg/kg following foliar application. The bioconcentration factor exceeded 1, with values ranging from 1.2 to 23.9 for root application and 6.4 to 164.0 for foliar application, indicating a significant role in the absorption and accumulation processes. The translocation factor data, which were <1, suggest limited the translocations within pakchoi plants. The limitation may be attributed to the hydrophobic properties of penthiopyrad (log Kow = 3.86), as evidenced by its predominant distribution in the subcellular solid fractions of pakchoi tissues, accounting for 93.1% to 99.5% of the total proportion. Six metabolites (753-A-OH, M12, 754-T-DO, M11, PCA, and PAM) were identified in this study as being formed during this process. These findings provide valuable insights into the absorption, translocation, and metabolism of penthiopyrad in pakchoi.

Comprehensive study of chiral herbicide flusulfinam uptake, translocation, degradation, and subcellular distribution in rice (Oryza sativa L.).

The biological behavior of flusulfinam, a potential commercial chiral herbicide for rice, has not been well explored. Herein, the uptake of chiral flusulfinam by rice and its transport, degradation, and subcellular distribution in rice (Oryza sativa L.) were investigated. The enantiomeric fraction (EF) in roots was 0.54 during 0 d to 7 d in hydroponic laboratory conditions. The bioconcentration factor of flusulfinam enantiomers was 2.1, suggesting an absence of observed enantioselectivity in the absorption process. Notably, the EF in the shoots decreased to 0.35 on the 7th day. The translocation factors of R- and S-flusulfinam were 0.12 and 0.27, respectively, indicating a preferential transfer of the S-flusulfinam from the root to the shoot. Flusulfinam was identified in the root after spraying. The translocation factors of R- and S-flusulfinam were consistently similar, signifying the capacity for downward movement without enantioselectivity. Interestingly, the degradation half-lives of R- and S-flusulfinam in the total plant were 5.50 and 5.06 d (p < 0.05), respectively, supporting the preferential degradation of S-flusulfinam throughout the total plant. Flusulfinam primarily entered the roots via the apoplastic pathway and was subsequently transported within the plant through aquaporins and ion channels. The subcellular distribution experiment revealed the predominant accumulation of flusulfinam enantiomers in soluble components (84%) with no enantioselectivity in these processes. There was upregulation lipid transfer protein-2 and carboxylesterases15 genes, which could explain the preferential transport and degradation of S-flusulfinam. This study is important in assessing the environmental risk associated with flusulfinam and ensuring food safety.

Subcellular Localization of Thioredoxin/Thioredoxin Reductase System-A Missing Link in Endoplasmic Reticulum Redox Balance.

The lumen of the endoplasmic reticulum (ER) is usually considered an oxidative environment; however, oxidized thiol-disulfides and reduced pyridine nucleotides occur there parallelly, indicating that the ER lumen lacks components which connect the two systems. Here, we investigated the luminal presence of the thioredoxin (Trx)/thioredoxin reductase (TrxR) proteins, capable of linking the protein thiol and pyridine nucleotide pools in different compartments. It was shown that specific activity of TrxR in the ER is undetectable, whereas higher activities were measured in the cytoplasm and mitochondria. None of the Trx/TrxR isoforms were expressed in the ER by Western blot analysis. Co-localization studies of various isoforms of Trx and TrxR with ER marker Grp94 by immunofluorescent analysis further confirmed their absence from the lumen. The probability of luminal localization of each isoform was also predicted to be very low by several in silico analysis tools. ER-targeted transient transfection of HeLa cells with Trx1 and TrxR1 significantly decreased cell viability and induced apoptotic cell death. In conclusion, the absence of this electron transfer chain may explain the uncoupling of the redox systems in the ER lumen, allowing parallel presence of a reduced pyridine nucleotide and a probably oxidized protein pool necessary for cellular viability.

Exogenous Application of Amino Acids Alleviates Toxicity in Two Chinese Cabbage Cultivars by Modulating Cadmium Distribution and Reducing Its Translocation.

Plants communicate underground by secreting multiple amino acids (AAs) through their roots, triggering defense mechanisms against cadmium (Cd) stress. However, the specific roles of the individual AAs in Cd translocation and detoxification remain unclear. This study investigated how exogenous AAs influence Cd movement from the roots to the shoots in Cd-resistant and Cd-sensitive Chinese cabbage cultivars (Jingcui 60 and 16-7 cultivars). The results showed that methionine (Met) and cysteine (Cys) reduced Cd concentrations in the shoots of Jingcui 60 by approximately 44% and 52%, and in 16-7 by approximately 43% and 32%, respectively, compared to plants treated with Cd alone. However, threonine (Thr) and aspartic acid (Asp) did not show similar effects. Subcellular Cd distribution analysis revealed that AA supplementation increased Cd uptake in the roots, with Jingcui 60 preferentially storing more Cd in the cell wall, whereas the 16-7 cultivar exhibited higher Cd concentrations in the organelles. Moreover, Met and Cys promoted the formation of Cd-phosphate in the roots of Jingcui 60 and Cd-oxalate in the 16-7 cultivar, respectively. Further analysis showed that exogenous Cys inhibited Cd transport to the xylem by downregulating the expression of HMA2 in the roots of both cultivars, and HMA4 in the 16-7 cultivar. These findings provide insights into the influence of exogenous AAs on Cd partitioning and detoxification in Chinese cabbage plants.

Uptake, subcellular distribution, and fate of tetracycline in two wetland plants supplemented with microbial agents: Effect and mechanism.

The use of wetland plants in the context of phytoremediation is effective in the removal of antibiotics from contaminated water. However, the effectiveness and efficiency of many of these plants in the removal of antibiotics remain undetermined. In this study, the effectiveness of two plants-Phragmites australis and Iris pseudacorus-in the removal of tetracycline (TC) in hydroponic systems was investigated. The uptake of TC at the roots of I. pseudacorus and P. australis occurred at concentrations of 588.78 and 106.70 µg/g, respectively, after 7-day exposure. The higher uptake of TC in the root of I. pseudacorus may be attributed to its higher secretion of root exudates, which facilitate conditions conducive to the reproduction of microorganisms. These rhizosphere-linked microorganisms then drove the TC uptake, which was higher than that in the roots of P. australis. By elucidating the mechanisms underlying these uptake-linked outcomes, we found that the uptake of TC for both plants was significantly suppressed by metabolic and aquaporin inhibition, suggesting uptake and transport of TC were active (energy-dependent) and passive (aquaporin-dominated) processes, respectively. The subcellular distribution patterns of I. pseudacorus and P. australis in the roots were different, as expressed by differences in organelles, cell wall concentration levels, and transport-related dynamics. Additionally, the microbe-driven enhancement of the remediation capacities of the plants was studied comprehensively via a combined microbial-phytoremediation hydroponic system. We confirmed that the microbial agents increased the secretion of root exudates, promoting the variation of TC chemical speciation and thus enhancing the active transport of TC. These results contribute toward the improved application of wetland plants in the context of antibiotic phytoremediation.

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MiRNAs are a class of small non-coding RNAs, which regulate gene expression post-transcriptionally by partial complementary base pairing. Aberrant miRNA expressions have been reported in tumor tissues and peripheral blood of cancer patients. In recent years, artificial intelligence algorithms such as machine learning and deep learning have been widely used in bioinformatic research. Compared to traditional bioinformatic tools, miRNA target prediction tools based on artificial intelligence algorithms have higher accuracy, and can successfully predict subcellular localization and redistribution of miRNAs to deepen our understanding. Additionally, the construction of clinical models based on artificial intelligence algorithms could significantly improve the mining efficiency of miRNA used as biomarkers. In this article, we summarize recent development of bioinformatic miRNA tools based on artificial intelligence algorithms, focusing on the potential of machine learning and deep learning in cancer-related miRNA research.

Selenium uptake, translocation, subcellular distribution and speciation in winter wheat in response to phosphorus application combined with three types of selenium fertilizer.

BACKGROUND: Selenium (Se) deficiency causes a series of health disorders in humans, and Se concentrations in the edible parts of crops can be improved by altering exogenous Se species. However, the uptake, transport, subcellular distribution and metabolism of selenite, selenate and SeMet (selenomethionine) under the influence of phosphorus (P) has not been well characterized. RESULTS: The results showed that increasing the P application rate enhanced photosynthesis and then increased the dry matter weight of shoots with selenite and SeMet treatment, and an appropriate amount of P combined with selenite treatment increased the dry matter weight of roots by enhancing root growth. With selenite treatment, increasing the P application rate significantly decreased the concentration and accumulation of Se in roots and shoots. P1 decreased the Se migration coefficient, which could be attributed to the inhibited distribution of Se in the root cell wall, but increased distribution of Se in the root soluble fraction, as well as the promoted proportion of SeMet and MeSeCys (Se-methyl-selenocysteine) in roots. With selenate treatment, P0.1 and P1 significantly increased the Se concentration and distribution in shoots and the Se migration coefficient, which could be attributed to the enhanced proportion of Se (IV) in roots but decreased proportion of SeMet in roots. With SeMet treatment, increasing the P application rate significantly decreased the Se concentration in shoots and roots but increased the proportion of SeCys2 (selenocystine) in roots. CONCLUSION: Compared with selenate or SeMet treatment, treatment with an appropriate amount of P combined with selenite could promote plant growth, reduce Se uptake, alter Se subcellular distribution and speciation, and affect Se bioavailability in wheat.

New Insights into the Accumulation, Transport, and Distribution Mechanisms of Hexafluoropropylene Oxide Homologues, Important Alternatives to Perfluorooctanoic Acid, in Lettuce (Lactuca sativa L.).

Hexafluoropropylene oxide (HFPO) homologues, which are important alternatives to perfluorooctanoic acid, have been frequently identified in crops. Although exposure to HFPO homologues via crops may pose non-negligible threats to humans, their impact on crops is still unknown. In this study, the accumulation, transport, and distribution mechanisms of three HFPO homologues in lettuce were investigated at the plant, tissue, and cell levels. More specifically, HFPO trimer acid and HFPO tetramer acid were primarily fixed in roots and hardly transported to shoots (TF, 0.06-0.63). Conversely, HFPO dimer acid (HFPO-DA) tended to accumulate in lettuce shoots 2-264 times more than the other two homologues, thus resulting in higher estimated daily intake values. Furthermore, the dissolved organic matter derived from root exudate enhanced HFPO-DA uptake by increasing its desorption fractions in the rhizosphere. The transmembrane uptake of HFPO homologues was controlled by means of a transporter-mediated active process involving anion channels, with the uptake of HFPO-DA being additionally facilitated by aquaporins. The higher accumulation of HFPO-DA in shoots was attributed to the larger proportions of HFPO-DA in the soluble fraction (55-74%) and its higher abundance in both vascular tissues and xylem sap. Our findings expand the understanding of the fate of HFPO homologues in soil-crop systems and reveal the underlying mechanisms of the potential exposure risk to HFPO-DA.

Cadmium tolerance in Elodea canadensis Michx: Subcellular distribution and metabolomic analysis.

The aquatic plant Elodea canadensis is considered a good candidate for ecotoxicological investigations. Cadmium (Cd) is a widespread contaminant in aquatic systems. In this study, to better elucidate the underlying tolerance mechanism and molecular impact of environmentally relevant Cd concentration in aquatic plants, subcellular distribution, chemical forms, and gas chromatography-mass spectrometry-based non-targeted metabolomics profiles were comprehensively analyzed in E. canadensis subjected to 0 and 10 µM Cd treatment for 5 d. Subcellular fractionation analysis of Cd-containing leaves showed that 67% of Cd was compartmentalized in cell wall followed by the soluble fraction (24 %) and organelles (9 %). The majority of Cd (90 %) was found in the extraction using 1 M NaCl. Metabolomic analysis using unsupervised principal component analyses and a supervised partial least squares discriminant analysis revealed clear differences in metabolic profiles between the two groups, demonstrating the metabolic effects of Cd. The 155 identified compounds altered by Cd were mainly from primary metabolism, including sugars, amino acids, organic acids, and their derivatives. Secondary metabolites such as polyphenols and phenolamides were also detected. The massive up-regulation of metabolites, including trehalose, proline, sarcosine, nicotianamine, putrescine, α-ketoglutaric acid, citric acid, and phytol might represent a detoxification mechanism. These findings highlighted the mechanistic strategies that E. canadensis employs to defend against Cd toxicity.

Transcriptomic analysis reveals the molecular mechanisms of Boehmeria nivea L. in response to antimonite and antimonate stresses.

Soil antimony (Sb) pollution is a global concern that threatens food security and human health. Boehmeria nivea L. (ramie) is a promising phytoremediation plant exhibiting high tolerance and enrichment capacity for Sb. To reveal the molecular mechanisms and thus enhance the ramie uptake, transport, and detoxification of Sb with practical strategies, a hydroponic experiment was conducted to compare the physiological and transcriptomic responses of ramie towards antimonite (Sb(Ⅲ)) and antimonate (Sb(Ⅴ)). Phenotypic results showed that Sb(Ⅲ) had a stronger inhibitory effect on the growth of ramie. Root Sb content under Sb(Ⅲ) was 2.43 times higher than that in Sb(Ⅴ) treatment. Based on the ribonucleic acid sequencing (RNA-Seq) technique, 3915 and 999 significant differentially expressed genes (DEGs) were identified under Sb(Ⅲ) and Sb(Ⅴ), respectively. Transcriptomic analysis revealed that ramie showed different adaptation strategies to Sb(Ⅲ) and Sb(V). Key DEGs and their involved pathways such as catalytic activity, carbohydrate metabolisms, phenylpropanoid biosynthesis, and cell wall modification were identified to perform crucial roles in Sb tolerance and detoxification. Two heavy metal-associated domain-type genes, six heavy metal-associated isoprenylated plant proteins, and nine ABC transporters showed possible roles in the transport and detoxification of Sb. The significant upregulation of NRAMP5 and three NIPs suggested their roles in the transport of Sb(V). This study is the basis for future research to identify the exact genes and biological processes that can effectively enhance Sb accumulation or improve plant tolerance to Sb, thereby promoting the phytoremediation of Sb-polluted soils.

Uptake, tolerance, and detoxification mechanisms of antimonite and antimonate in Boehmeria nivea L.

Boehmeria nivea L. (ramie) is a promising phytoremediation plant for antimony (Sb)-contaminated soils. However, the uptake, tolerance, and detoxification mechanisms of ramie to Sb, which are the basis for finding efficient phytoremediation strategies, remain unclear. In the present study, ramie was exposed to 0, 1, 10, 50, 100, and 200 mg/L of antimonite (Sb(III)) or antimonate (Sb(V)) for 14 days in hydroponic culture. The Sb concentration, speciation, subcellular distribution, and antioxidant and ionomic responses in ramie were investigated. The results illustrated that ramie was more effective in the uptake of Sb(III) than Sb(V). Most of the Sb accumulated in ramie roots, with the highest level reaching 7883.58 mg/kg. Sb(V) was the predominant species in leaves, with 80.77-96.38% and 100% in the Sb(III) and Sb(V) treatments, respectively. Immobilization of Sb on the cell wall and leaf cytosol was the primary mechanism of accumulation. Superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) contributed significantly to root defense against Sb(III), while CAT and glutathione peroxidase (GPX) were the major antioxidants in leaves. CAT and POD played crucial roles in the defense against Sb(V). B, Ca, K, Mg, and Mn in Sb(V)-treated leaves and K and Cu in Sb(III)-treated leaves may be related to the biological processes of Sb toxicity mitigation. This study is the first to investigate the ionomic responses of plants toward Sb and could provide valuable information for the phytoremediation of Sb-polluted soils.

Effect of foliar and root exposure to polymethyl methacrylate microplastics on biochemistry, ultrastructure, and arsenic accumulation in Brassica campestris L.

Despite the serious risk of microplastic pollution in the roots and leaves of crops, the phytotoxicity of microplastics (introduced via different exposure routes) in leafy vegetables remain insufficiently understood. Here, the effects of the root and foliar exposure of polymethyl methacrylate microplastic (PMMAMPs) on phytotoxicity, As accumulation, and subcellular distribution were investigated in rapeseed (Brassica campestris L). The relative chlorophyll content under PMMAMPs treatment decreased with time, and the 0.05 g L-1 root exposure decreased it significantly (by 9.97-20.48%, P < 0.05). In addition, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and ascorbate peroxidase (APX) activities in rapeseed were more sensitive to PMMAMPs introduced through root exposure than through foliar exposure. There was dose-dependent ultrastructural damage, and root exposure had a greater impact than foliar exposure on root tip cells and chloroplasts. PMMAMPs entered the shoots and roots of rapeseed through root exposure. Under foliar exposure, PMMAMPs promoted As accumulation in rapeseed by up to 75.6% in shoots and 68.2% in roots compared to that under control (CK). As content in cell wall under PMMAMP treatments was 3.6-5.3 times higher than that of CK, as indicated by subcellular component results. In general, root exposure to PMMAMPs resulted in a stronger physiological impact and foliar exposure led to increased As accumulation in rapeseed.

Accumulation and subcellular distribution of cadmium in rygegrass induced by Aspergillus niger TL-F2 and Aspergillus flavus TL-F3.

Although plant growth-promoting fungi can greatly accelerate the ryegrass bioaccumulation of cadmium (Cd), the underlying mechanisms are not yet well documented. Therefore, we performed a 20-days hydroponic experiment to investigate the effects of Aspergillus niger TL-F2 (A. niger TL-F2) and Aspergillus flavus TL-F3 (A. flavus TL-F3) on accumulation/subcellular distribution of Cd by annual ryegrass Dongmu 70 at different Cd concentrations (0, 2.5, and 5 mg L-1). Results indicated that both fungal strains promoted ryegrass biomass/growth by about 60%. Furthermore, we found that ryegrass roots (17.8-37.1 µg pot-1) had a significantly higher capability for Cd uptake than the shoots (1.66-5.45 µg pot-1) (p < 0.05). Of total Cd in ryegrass plants, 44-67% was in soluble form, 24-37% was in cell wall, and 8.5-25.5% was in organelles. Compared with non-fungus ryegrass, cell wall and soluble Cd fractions in fungus-inoculated roots increased and decreased by 13.5-44% and 21.5-26.4%, respectively. Besides, fungus inoculation generally increased the content of cell wall and soluble Cd fractions in ryegrass shoots. Altogether, the study concludes that inoculation of fungus in ryegrass is a promising approach to improve phytoremediation of Cd contaminated environments.Novelty statement Previous study by Han et al. (2018) examined the resistance of ryegrass plant to Cd stress after its inoculation with Aspergillus aculeatus. In this study, using a hydroponic experiment, we examined the effects of co-application of two species of Aspergillus fungi. i.e. A. niger TL-F2 and A. flavus TL-F3 on ryegrass growth/biomass, Cd absorption by ryegrass shoots and roots, and subcellular distribution of Cd in ryegrass roots and shoots.

Salicylic Acid Enhances Cadmium Tolerance and Reduces Its Shoot Accumulation in Fagopyrum tataricum Seedlings by Promoting Root Cadmium Retention and Mitigating Oxidative Stress.

Soil cadmium (Cd) contamination seriously reduces the production and product quality of Tartary buckwheat (Fagopyrum tataricum), and strategies are urgently needed to mitigate these adverse influences. Herein, we investigated the effect of salicylic acid (SA) on Tartary buckwheat seedlings grown in Cd-contaminated soil in terms of Cd tolerance and accumulation. The results showed that 75-100 µmol L-1 SA treatment enhanced the Cd tolerance of Tartary buckwheat, as reflected by the significant increase in plant height and root and shoot biomass, as well as largely mitigated oxidative stress. Moreover, 100 µmol L-1 SA considerably reduced the stem and leaf Cd concentration by 60% and 47%, respectively, which is a consequence of increased root biomass and root Cd retention with promoted Cd partitioning into cell wall and immobile chemical forms. Transcriptome analysis also revealed the upregulation of the genes responsible for cell wall biosynthesis and antioxidative activities in roots, especially secondary cell wall synthesis. The present study determines that 100 µmol L-1 is the best SA concentration for reducing Cd accumulation and toxicity in Tartary buckwheat and indicates the important role of root in Cd stress in this species.

Dynamic and Comparative Transcriptome Analyses Reveal Key Factors Contributing to Cadmium Tolerance in Broomcorn Millet.

Broomcorn millet (Panicum miliaceum L.) has great potential in Cd phytoextraction, but its mechanisms are largely unknown. Two contrasting broomcorn millet varieties, 'Ningmi6' (Cd-sensitive variety) and '4452' (Cd-tolerant variety), were investigated through morphological, physiological, and transcriptomic analyses to determine the factors responsible for their differential Cd tolerance and translocation. The Cd-tolerant variety can accumulate more Cd, and its cell wall and vacuole component Cd proportions were higher compared with the Cd-sensitive variety. Under Cd stress, the glutathione content and peroxidase activity of the Cd-tolerant variety were significantly higher than those of the Cd-sensitive variety. Additionally, weighted gene co-expression network analysis (WGCNA) revealed hub modules that were associated with Cd stress and/or variety. Notably, genes involved in these hub modules were significantly enriched for roles in glutathione metabolism, phenylpropanoid biosynthesis, ABC transport, and metal ion transport process. These results suggested that regulation of genes associated with cell wall precipitation and vacuole compartmentalization may increase Cd tolerance and reduce Cd translocation in the Cd-tolerant variety, although it can absorb more Cd. This study provides a foundation for exploring molecular mechanisms of Cd tolerance and transport in broomcorn millet and new insights into improving Cd phytoremediation with this crop through genetic engineering.

Exopolysaccharides from Lactobacillus plantarum reduces cadmium uptake and mitigates cadmium toxicity in rice seedlings.

Exopolysaccharides (EPSs) can be used as effective exogenous substances to alleviate the toxic effect of cadmium (Cd) on rice and other crops, thus improving plant growth characteristics under stress conditions, and reducing the accumulation of Cd in grains, but the underlying mechanism is still unclear. In the present work, the effects of EPSs from Lactobacillus plantarum on the efficiency of Cd absorption and distribution in rice seedlings under Cd stress were investigated. The results revealed that growth of rice seedlings was severely inhibited by exposure to Cd, resulting in the decrease of plant height, leaf length and biomass. This inhibition phenomenon was alleviated by the addition of EPSs from L. plantarum LPC-1. The underlying mechanism might be that EPSs could facilitate the accumulation efficiency of Cd in rice roots and reduce the transportation rate of Cd from root to leaves, therefore decreasing the Cd content in leaves. Further research showed that Cd contents in the cell wall fraction of the rice seedling root were increased by the addition of EPSs, while the proportions of Cd in the cell organelle and cell soluble component were reduced. Application of EPSs promotes the proportion of pectate- and protein- integrated Cd in rice roots. While the content of water-soluble Cd, which is more toxic to plants, decreased continuously both in roots and leaves. Our study clearly confirmed the positive effects of EPSs on alleviating Cd toxicity and decreasing Cd translocation in rice above-ground parts. Furthermore, the subcellular distribution and chemical forms of Cd in different rice seedlings parts were also affected by the addition of EPSs, which might be an important potential mechanism for EPSs in respect of alleviating Cd toxicity for rice. These findings provided a foundation for the application of exogenous substances on improving the growth performance of crops under heavy metal stress.

Supramolecular Assembly of Organoplatinum(II) Complexes for Subcellular Distribution and Cell Viability Monitoring with Differentiated Imaging.

The ability to precisely control the subcellular distribution of luminous materials presents unprecedented advantages for understanding cell biology and disease therapy. We introduce a luminescence tool for subcellular distribution imaging and differentiation of live and dead cells, utilizing cationic organoplatinum(II) complexes that exhibit well-defined monomeric to aggregate nanostructures along with concentration-dependent switchable luminescence from green to red due to assembly via PtII ⋅⋅⋅PtII and π-π stacking interactions. One of the complexes was chosen to demonstrate the unique lysosome-to-nucleus subcellular re-distribution and imaging capability in live and dead cells, respectively, which represents the first example to discriminate the subcellular localization of platinum(II) complexes through differential luminescence response. These new findings facilitate the fundamental understanding of self-assembly behaviors of platinum(II) complexes for potential subcellular detection assays.

Subcellular Distribution of Dietary Methyl-Mercury in Gammarus fossarum and Its Impact on the Amphipod Proteome.

The transfer of methyl-Hg (MeHg) from food is central for its effects in aquatic animals, but we still lack knowledge concerning its impact on invertebrate primary consumers. In aquatic environments, cell walls of plants are particularly recalcitrant to degradation and as such remain available as a food source for long periods. Here, the impact at the proteomic level of dietary MeHg in Gammarus fossarum was established and linked to subcellular distribution of Hg. Individuals of G. fossarum were fed with MeHg in cell wall or intracellular compartments of Elodea nuttallii. Hg concentrations in subcellular fractions were 2 to 6 times higher in animals fed with cell wall than intracellular compartments. At the higher concentrations tested, the proportion of Hg in metal-sensitive fraction increased from 30.0 ± 6.1 to 41.0 ± 5.7% for individuals fed with intracellular compartment, while biologically detoxified metal fraction increased from 30.0 ± 6.1 to 50.0 ± 2.8% when fed with cell wall compartment. Data suggested that several thresholds of proteomic response are triggered by increased bioaccumulation in each subcellular fraction in correlation with Hg exclusively bound to the metal-sensitive fraction, while the increase of biologically detoxified metal likely had a cost for fitness. Proteomics analysis supported that the different binding sites and speciation in shoots subsequently resulted in different fate and cellular toxicity pathways to consumers. Our data confirmed that Hg bound in cell walls of plants can be assimilated by G. fossarum, which is consistent with its feeding strategy, hence pointing cell walls as a significant source for Hg transfers and toxicity in primary consumers. The high accumulation of Hg in macrophytes makes them a risk for food web transfer in shallow ecosystems. The present results allowed gaining new insights into the effects and uptake mechanisms of MeHg in aquatic primary consumers.