Overexpression of SmZIP plays important roles in Cd accumulation and translocation, subcellular distribution, and chemical forms in transgenic tobacco under Cd stress.

Plant ZIP genes represent an important transporter family and may be involved in cadmium (Cd) accumulation and Cd resistance. In order to explore the function of SmZIP isolated from Salix matsudana, the roles of SmZIP in Cd tolerance, uptake, translocation, and distribution were determined in the present investigation. The transgenic SmZIP tobacco was found to respond to external Cd stress differently from WT tobacco by exhibiting a higher growth rate and more vigorous phenotype. The overexpression of SmZIP in tobacco resulted in the reduction of Cd stress-induced phytotoxic effects. Compared to WT tobacco, the Cd content of the root, stem, and leaf in the transgenic tobacco increased, and the zinc, iron, copper, and manganese contents also increased. The assimilation factor, translocation factor and bioconcentration factor of Cd were improved. The scanning electron microscopy and energy dispersive X-ray analysis results of the root maturation zone exposed to Cd for 24 h showed that Cd was transferred through the root epidermis, cortex, and vascular cylinder and migrated to the aboveground parts via the vascular cylinder, resulting in the transgenic tobacco accumulating more Cd than the WT plants. Based on the transverse section of the leaf main vein and leaf blade, Cd was transported through the vascular tissues to the leaves and accumulated more greatly in the leaf epidermis, but less in the leaf mesophyll cells, following the overexpression of SmZIP to reduce the photosynthetic toxicity. The overexpression of SmZIP resulted in the redistribution of Cd at the subcellular level, a decrease in the percentage of Cd in the cell wall, and an increase of the Cd in the soluble fraction in both the roots and leaves. It also changed the percentage composition of different Cd chemical forms by elevating the proportion of Cd extracted using 2% HAc and 0.6 mol/L HCl, but lowering that of the Cd extracted using 1 mol/L NaCl in both the leaves and roots under 10 and 100 µmol/L Cd stress for 28 d. The results implied that SmZIP played important roles in advancing Cd uptake, accumulation, and translocation, as well as in enhancing Cd resistance by altering the Cd subcellular distribution and chemical forms in the transgenic tobacco. The study will be useful for future phytoremediation applications to clean up Cd-contaminated soil.

Characterisation of early responses in lead accumulation and localization of Salix babylonica L. roots.

BACKGROUND: Lead (Pb) is a harmful pollutant that disrupts normal functions from the cell to organ levels. Salix babylonica is characterized by high biomass productivity, high transpiration rates, and species specific Pb. Better understanding the accumulating and transporting Pb capability in shoots and roots of S. babylonica, the toxic effects of Pb and the subcellular distribution of Pb is very important. RESULTS: Pb exerted inhibitory effects on the roots and shoots growth at all Pb concentrations. According to the results utilizing inductively coupled plasma atomic emission spectrometry (ICP-AES), S. babylonica can be considered as a plant with great phytoextraction potentials as translocation factor (TF) value > 1 is observed in all treatment groups throughout the experiment. The Leadmium™ Green AM dye test results indicated that Pb ions initially entered elongation zone cells and accumulated in this area. Then, ions were gradually accumulated in the meristem zone. After 24 h of Pb exposure, Pb accumulated in the meristem zone. The scanning electron microscopy (SEM) and energy-dispersive X-ray analyses (EDXA) results confirmed the fluorescent probe observations and indicated that Pb was localized to the cell wall and cytoplasm. In transverse sections of the mature zone, Pb levels in the cell wall and cytoplasm of epidermal cells was the lowest compared to cortical and vessel cells, and an increasing trend in Pb content was detected in cortical cells from the epidermis to vascular cylinder. Similar results were shown in the Pb content in the cell wall and cytoplasm of the transverse sections of the meristem. Cell damage in the roots exposed to Pb was detected by propidium iodide (PI) staining, which was in agreement with the findings of Pb absorption in different zones of S. babylonica roots under Pb stress. CONCLUSION: S. babylonica L. is observed as a plant with great potential of Pb-accumulation and Pb-tolerance. The information obtained here of Pb accumulation and localization in S. babylonica roots can furthers our understanding of Pb-induced toxicity and its tolerance mechanisms, which will provide valuable and scientific information to phytoremediation investigations of other woody plants under Pb stress.

Accumulation and cellular toxicity of aluminum in seedling of Pinus massoniana.

BACKGROUND: Masson pine (Pinus massoniana) is one of the most important timber species with adaptable, fast growing, versatile advantages in southern China. Despite considerable research efforts, the cellular and molecular mechanisms of A1 toxicity and resistance in P. massoniana are still poorly understood. The effects of Al on uptake and translocation of Al and other minerals, cell division and nucleolus in P. massoniana were investigated. RESULTS: The results indicated that Al accumulated mainly in the roots, and small amounts were transported to aboveground organs. In the presence of Al, the contents of Mg and Fe in stems increased and decreased in roots. Accumulation of Mn in the organs was inhibited significantly. Evidence from cellular experiments showed that Al had an inhibitory effect on the root growth at all concentrations (10⁻5 - 10⁻² M) used. Chromosome fragments, chromosome bridges, C-mitosis and chromosome stickiness were induced during mitosis in the root tip cells. Al induced the formation of abnormal microtubule (MT) arrays, consisting of discontinuous wavy MTs or short MT fragments at the cell periphery. MT organization and function of the mitotic spindle and phragmoplast were severely disturbed. The nucleolus did not disaggregate normally and still remained its characteristic structure during metaphase. Nucleolar particles containing argyrophilic proteins were accumulated and leached out from the nucleus to the cytoplasm. Evidence confirmed that these proteins contained nucleophosmin (B23), nucleolin (C23) and fibrillarin. Western immunoblot analysis revealed that the contents of three nucleolar proteins increased significantly. CONCLUSION: Based on the information provided in this article, it is concluded that root tips of plants are the most sensitive organ to environmental stresses and the accumulation of Al ions primarily is in roots of P. massoniana, and small amounts of Al are transported to aboveground. Root apical meristems play a key role in the immediate reaction to stress factors by activating signal cascades to the other plant organs. Al induces a series of the cellular toxic changes concerning with cell division and nucleolus. The data presented above can be also used as valuable and early markers in cellular changes induced by metals for the evaluation of metal contamination.

Effects of lead on the morphology and structure of the nucleolus in the root tip meristematic cells of Allium cepa L.

To study the toxic mechanisms of lead (Pb) in plants, the effects of Pb on the morphology and structure of the nucleolus in root tip meristematic cells of Allium cepa var. agrogarum L. were investigated. Fluorescence labeling, silver-stained indirect immunofluorescent microscopy and western blotting were used. Fluorescence labeling showed that Pb ions were localized in the meristematic cells and the uptake and accumulation of Pb increased with treatment time. At low concentrations of Pb (1-10 µM) there were persistent nucleoli in some cells during mitosis, and at high concentration (100 µM) many of the nucleolar organizing regions were localized on sticky chromosomes in metaphase and anaphase cells. Pb induced the release of particles containing argyrophilic proteins to be released from the nucleus into the cytoplasm. These proteins contained nucleophosmin and nucleolin. Pb also caused the extrusion of fibrillarin from the nucleus into the cytoplasm. Western blotting demonstrated the increased expression of these three major nucleolar proteins under Pb stress.

The interrelationship between sleep disturbance symptoms and aggression before and after the campus closure of the COVID-19 pandemic: insight from a cross-lagged panel network model.

Background: The COVID-19 pandemic is detrimental to sleep quality and increases aggression among college students. Nevertheless, relevant studies were rare. Hence, we collected longitudinal data during and post-campus closure in the current study to investigate the relationship between sleep disturbance and aggression. Methods: Data from 665 college students (59.2% females, Meanage = 19.01, SD age = 1.25) were collected before (wave 1) and after (wave 2) the campus closure of COVID-19. All participants were asked to fill out the Buss-Perry Aggression Questionnaire and the Youth Self-Rating Insomnia Scale. Two symptom networks and a cross-lagged panel network were formed and tested. Results: Hostility has the highest centrality in the symptom network both in waves 1 and 2, and it bridges sleep disturbance and aggression. "Easily be woken" - "wake up too early" and "wake up with tired" - "function hindrance" are two important symptom associations in networks of waves 1 and 2. All symptoms except "difficulty in falling asleep" and "easily be woken" ameliorated after closure. Moreover, "physical aggression" and "hostility" can trigger other symptoms in wave 2. Conclusion: As the first study about aggression and sleep disturbance in the background of COVID-19, we provide valuable information about the relationship between sleep disturbance and aggression on the symptom dimension.

Fast optical cooling of nanomechanical cantilever with the dynamical Zeeman effect.

We propose an efficient optical electromagnetically induced transparency (EIT) cooling scheme for a cantilever with a nitrogen-vacancy center attached in a non-uniform magnetic field using dynamical Zeeman effect. In our scheme, the Zeeman effect combined with the quantum interference effect enhances the desired cooling transition and suppresses the undesired heating transitions. As a result, the cantilever can be cooled down to nearly the vibrational ground state under realistic experimental conditions within a short time. This efficient optical EIT cooling scheme can be reduced to the typical EIT cooling scheme under special conditions.

Ca alleviated Cd-induced toxicity in Salix matsudana by affecting Cd absorption, translocation, subcellular distribution, and chemical forms.

Cadmium (Cd), a ubiquitous and highly toxic heavy metal pollutant, is toxic to animals and plants. Calcium (Ca) is an essential component for plant growth and reduces plant Cd absorption by competing with Cd. To gain deeper insight into the effects of Ca on Cd absorption, translocation, subcellular distribution, and chemical forms in S. matsudana seedlings under Cd stress, an investigation was conducted on these properties. Adding Ca alleviated Cd physiological toxicity in S. matsudana, reduced Cd absorption, increased the translocation from roots to shoots, lead to subcellular redistribution of Cd by increasing the proportion of Cd in soluble fractions but decreasing Cd in the cell wall and changed the chemical forms of Cd from 0.6 mol/L HCl- and 2% HAc-extracted Cd to 1 mol/L NaCl-extracted Cd. The energy dispersive X-ray analyses (EDXA) results revealed that after adding Ca, Cd was transferred through the root epidermis, cortex, endodermis, and vascular cylinder, transported to the shoots, and was highly accumulated in leaf epidermal and mesophyll cells, but less in leaf vein and guard cells. The genes involved in Cd uptake and xylem loading included NRAMP1, ZIP8, HMA2, and HMA4, which were up-regulated significantly (P < 0.05) in the Cd and Cd + Ca treatments compared to the control. The findings of this study provide new insight into the mechanism that Ca alleviates Cd toxicity in woody tree species, as well as propose an important prospect of Ca addition for improving the phytoremediation of Cd contamination.

The combination of graphene oxide and preservatives can further improve the preservation of cut flowers.

It is reported that the use of nanomaterials can extend the vase life of fresh-cut flowers. Graphene oxide (GO) is one of these nanomaterials that aid in promoting water absorption and antioxidation during the preservation of fresh-cut flowers. In this investigation, the three mainstream brands of preservatives commercially available on the market ("Chrysal," "Floralife," and "Long Life") in combination with low concentrations of GO (0.15 mg/L) were used to preserve fresh-cut roses. The results showed that the three brands of preservatives had different degrees of freshness retention. Compared to the preservatives used alone, the combination of low concentrations of GO with the preservatives, especially in the L+GO group (with 0.15 mg/L GO added in the preservative solution of "Long life"), further improved the preservation of cut flowers. L+GO group showed less level of antioxidant enzyme activities, lower ROS accumulation and cell death rate, and higher relative fresh weight than the other groups, implying a better antioxidant and water balance abilities. GO attached to the xylem duct of flower stem, and reduced the blockage of xylem vessels by bacteria, which were determined by SEM (scanning electron microscopy) and FTIR (Fourier transform infrared) analysis. XPS (X-ray photoenergy spectra) analysis results proved that GO could enter the interior of flower stem through xylem duct, and when combined with "Long Life," the anti-oxidation protection ability of GO was enhanced, thus delaying ageing, and greatly extending the vase life of fresh-cut flowers. The study provides new insights into cut flower preservation using GO.

Cytological and physiological tolerance of transgenic tobacco to Cd stress is enhanced by the ectopic expression of SmZIP8.

Zrt and Irt-like proteins (ZIPs) are responsible for transporting various divalent metal cations. However, information about the characteristics of the cellular and physiological tolerance of plant ZIPs to Cd stress is still limited. The expression levels of SmZIP8 in Salix matsudana Koidz were upregulated by Cd stress. The complete length of SmZIP8 from S. matsudana was cloned, and transgenic tobacco was obtained by Agrobacterium-mediated transformation. Then, the tolerance to Cd stress of wild-type (WT) and transgenic tobacco seedlings was analyzed and compared by studying the cytotoxicity of the root tip cells, photosynthetic parameters, histochemical staining of O2- and H2O2, the activities of antioxidant enzymes, and malondialdehyde content under Cd stress. In comparison with WT tobacco, the ectopic expression of SmZIP8 in tobacco promoted the cytological tolerance of the transgenic tobacco to Cd stress by reducing cell damage, raising the mitotic indexes, and reducing the rate of chromosome aberration of the root cells. Meanwhile, the results of increased photosynthetic capacity, decreased oxidative damage, and activated antioxidant enzymes showed that the physiological tolerance of transgenic tobacco to Cd was enhanced. The principal component analysis for the above physiological parameters explained 96.08% of the total variance (PC1, 77.77%; PC2, 18.31%), indicating a significant difference in Cd tolerance abilities between the tobacco expressing SmZIP8 and WT tobacco. Therefore, SmZIP8 may be considered as an important genetic resource for the phytoremediation of Cd or other heavy metal pollution via the use of transgenic plants obtained through genetic transformation.

Tumor-targetable magnetoluminescent silica nanoparticles for bimodal time-gated luminescence/magnetic resonance imaging of cancer cells in vitro and in vivo.

Bimodal photoluminescence-magnetic resonance (MR) imaging technique has attracted tremendous attention due to its great potential in biomedical researches and clinical practices. Herein a novel multifunctional magnetoluminescent nanocomposite, FA-Gd-Tb@SiO2, was found to serve as an effective probe for bimodal time-gated luminescence/MR imaging of cancer cells in vitro and in vivo. The nanoprobe was designed by integrating a luminescent Tb3+ complex, a Gd(III)-based contrast agent and a tumor-targeting molecule, folic acid (FA), into a silica nanoparticle. The integration of these functional moieties allows the nanoprobe to be employed for specific imaging of cancer cells with background-free TGL and non-invasive MR imaging modes. In addition, the optical and magnetic properties were dramatically improved after implicating the newly synthesized nanoarchitecture. In vitro cellular TGL imaging demonstrated that the FA-Gd-Tb@SiO2 nanoprobe could recognize and accumulate in cancer cells overexpressing FA receptor. Furthermore, in vivo study revealed that the as-prepared nanoprobe was able to effectively enhance T1-weighted MR contrast and TGL intensity in tumor tissue, which might contribute to the precise detection and tracing of cancer cells, as well as diagnosis and therapy of tumor in clinical.

Uptake and accumulation and oxidative stress in garlic (Allium sativum L.) under lead phytotoxicity.

The effects of different concentrations of Pb on growth of Allium sativum L, Pb uptake and accumulation, antioxidant enzyme activity and malondialdehyde content were investigated. The results indicated that shoot growth at high concentration of Pb (10(-3) M) and roots growth at 10(-3) M and 10(-4) M Pb were significantly inhibited. Lead ions were accumulated mainly in the roots and only small amounts were translocated to bulbs and shoots. SOD activities in shoot and roots exposed to 10(-3) M Pb were observed to be high. Plants exposed to 10(-3) M Pb showed a significant increase in POD activity in roots versus the control and other Pb treatments. In roots, CAT activity and MDA concentration at 10(-3) M Pb is high significantly. The mechanisms of Pb toxicity and tolerance in garlic are briefly discussed.

Hexavalent chromium uptake and its effects on mineral uptake, antioxidant defence system and photosynthesis in Amaranthus viridis L.

The effects of different concentrations (10(-6)M, 10(-5)M and 10(-4)M) of K2Cr2O7Cr(VI) on some minerals (Mn, Fe, Cu and Zn), lipid peroxidation, activities of antioxidant enzymes, photosynthetic function, and chlorophyll fluorescence characteristics were investigated in hydroponically grown Amaranthus viridis L. Results indicated that chromium was accumulated primarily in roots. In the roots and shoots, the Cr content increased with the increasing Cr(VI) concentrations, and induced decrease of Mn, Fe, Cu and Zn. Chromium Cr(VI) induced oxidation stress and lipid peroxidation in A. viridis L. shown by the increased concentration of MDA. The increased activities of POD and SOD indicated that they could serve as important components of antioxidant defense mechanisms to minimize Cr induced oxidative injury. The net photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration were reduced only by high Cr(VI) treatments (10(-5)M and 10(-4)M). The chlorophyll fluorescence parameters Fv/Fm, Fv(')/Fm('), Phi PSII and qP, decreased in Cr(VI)-treated, but qN and NPQ showed an increase in Cr(VI) treated plants.

Effects of Cd(2+) on seedling growth of garlic (Allium sativum L.) and selected physiological and biochemical characters.

In this study, we determined the effects of Cd(2+) (from 10(-5) to 10(-3)M) on the growth of leaves and roots of garlic seedlings in Hoagland's nutrient solution. We also characterized the influences of Cd(2+) on a few key cellular activities, e.g., antioxidant enzymes, content of malondialdehyde (MDA), composition of photosynthetic pigments and fluorescence properties of chlorophyll on day 5, 10 and 15. The results indicated that the presence of 10(-3)M Cd(2+), but not other tested Cd(2+) concentrations, significantly decreased the development of leaves and roots of the seedlings. This level of Cd(2+) increased the activities of antioxidant enzymes and the level of MDA. With the exception of carotenoid on day 5, the presence of 10(-3)M Cd(2+) showed no significant effects on the contents of photosynthetic pigments. Intermediate concentrations of Cd(2+) caused variable effects, ranging from lowering to increasing the pigments in garlic seedlings. The presence of 10(-3)M Cd(2+), but not other tested concentrations, decreased efficiency of energy harvesting associated with photosystem II as measured by the ratio of variable to maximum chlorophyll fluorescence of intact leaves. However, Cd(2+) generated no definitive trends on photochemical quenching. Possible significance of experimental findings in relation to Cd(2+) level in garlic seedling is discussed.

Cadmium accumulation and its effects on metal uptake in maize (Zea mays L.).

The effects of different concentrations of Cd on growth of maize (Zea mays L.) and metal uptake were investigated. Cd accumulations in roots and shoots and the interactions among other metals (Mn, Fe, Cu and Zn) were analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The concentrations of cadmium chloride (CdCl(2).2.5H2O) used ranged from 10(-4) M to 10(-6) M. Cd had stimulatory effects during the first 5 days on root length of Nongda No. 108 at 10(-6) M and 10(-5) M Cd concentrations. Seedlings exposed to 10(-4) M Cd solution exhibited substantial growth reduction, and root growth even stopped. Root growth of Liyu No. 6 was stimulated at concentrations of 10(-5) M and 10(-6) M Cd during the entire experiment (15 days). Cadmium inhibited root growth of Liyu No. 6 at 10(-4) M Cd after 10 days of treatment. The Cd accumulation in roots and shoots of the two cultivars increased significantly (P < 0.05) with increasing Cd concentration and duration of treatment. Cadmium concentrated mainly in the roots, and small amounts were transferred to shoots. The proportion of Cd in the roots of Nongda No. 108 decreased with increases in Cd concentrations and duration of treatment, except for the group exposed to 10(-4) M Cd. In Liyu No. 6, the proportion of Cd in the root decreased progressively with an increase in Cd concentrations. Liyu No. 6 has a greater ability to remove Cd from solution and accumulate it when compared with Nongda No. 108. Liyu No. 6 can be considered a Cd-hyperaccumulator, according to the current accepted shoot concentration that defines hyperaccumulation as 0.01% (w/w) for cadmium. This cultivar, producing many roots and a high biomass and with great ability to accumulate Cd can play an important role in the treatment of soils stressed by Cd.