Screening of the proteins related to the cultivar-dependent cadmium accumulation of Brassica parachinensis L.

Cultivar-dependent cadmium (Cd) accumulation was principal in developing Cd-pollution safe cultivars (PSCs). Proteins related to different Cd accumulations of the low-Cd-accumulating (SJ19) and high-Cd-accumulating (CX4) cultivars were investigated by iTRAQ analysis. Higher Cd bioaccumulation factors and translocation factor in CX4 than in SJ19 were consistent with the cultivar-dependent Cd accumulations. The Cd uptake was promoted in CX4 due to its higher expression of Cd-binding proteins and the lower expression of Cd-efflux proteins in roots. What's more, significantly elevated thiol groups (PC2 and PC3) in CX4 under Cd stress might contribute to the high Cd accumulation in roots and the root-to-shoot translocation of Cd-PC complex. Up-regulated proteins involved in cellulose biosynthesis and pectin de-esterification in SJ19 enhanced the Cd sequestration of root cell walls, which was considered as the predominant strategy for reducing Cd accumulation in shoots. The present study provided novel insights in the cultivar-dependent Cd accumulation in shoots of B. parachinensis.

Cloning, characterization and expression analysis of metallothioneins from Ipomoea aquatica and their cultivar-dependent roles in Cd accumulation and detoxification.

To explore the possible roles of metallothioneins (MTs) played in cadmium (Cd) accumulation of water spinach, three IaMT genes, IaMT1, IaMT2 and IaMT3 in a high-shoot-Cd (T308) and a low-shoot-Cd accumulation cultivar (QLQ) were cloned, characterized, and quantitated. Gene expression analysis suggested that the expression of the IaMTs was differentially regulated by Cd stress in different cultivars, and T308 showed higher MTs expression overall. Furthermore, only shoot IaMT3 expression was cultivar dependent among the three IaMTs. Antioxidant analysis showed that the high production of IaMTs in T308 should be associated with its high oxidation resistance. The role of IaMTs in protecting against Cd toxicity was demonstrated in vitro via recombinant E. coli strains. The results showed that IaMT1 correlated with neither Cd tolerance nor Cd accumulation of E. coli, while IaMT2 conferred Cd tolerance in E. coli, IaMT2 and IaMT3 increased Cd accumulation in E. coli. These findings help to clarify the roles of IaMTs in Cd accumulation, and increase our understanding of the cultivar-dependent Cd accumulation in water spinach.

Dichloro-diphenyl-trichloroethanes (DDTs) in human hair and serum in rural and urban areas in South China.

Human hair has been employed as a biomarker for exposure to persistent organic pollutants (POPs), but information on the source of dichloro-diphenyl-trichloroethane (DDT) and its metabolites in hair is limited. The present study investigated the contamination of DDTs in human hair from a rural area and an urban area of South China and compared with those in human serum and indoor dust. The concentrations of ∑DDTs ranged from 2.30 to 489ng/g, with a median of 21.8ng/g in human hair. The ∑DDT concentrations (median=40.8ng/g) in female hair were significantly higher than those in male hair (median=20.6ng/g). There were significantly positive correlations between the concentrations of DDTs and ages in both the female and male hair, but the age-dependence for DDTs in serum was less significant. The profile of DDT analogues in female hair, differing from that in the male hair, was more similar to that in the indoor dust, suggesting a more important role of exogenous exposure in female hair. We estimated that exogenous source is responsible for approximately 11% and 20% of the burden of DDTs in the male and female hair, respectively. Adjusted multiple linear regression model showed significantly positive association between the p,p'-DDE concentrations in the paired hair and serum samples, indicating that endogenous origins are the primary sources of DDTs in the hair of the residents in the study areas. Our findings demonstrated that human hair is a reliable biomarker for body burden of DDTs and can be used in epidemiology research and retrospective assessment of DDT exposure.

Organic contaminants and heavy metals in indoor dust from e-waste recycling, rural, and urban areas in South China: Spatial characteristics and implications for human exposure.

The concentrations of several organic contaminants (OCs) and heavy metals were measured in indoor dust from e-waste recycling, rural, and urban areas in South China to illustrate the spatial characteristics of these pollutants and to further evaluate human exposure risks. The median concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE), and dechlorane plus (DPs) were 38.6-3560, 2360-30,100, 665-2720, and 19.5-1860ng/g, while the median concentrations of Cd, Pb, Cu, Cr, and Zn were 2.46-40.4, 206-1380, 217- 1200, 25.3-134, and 176-212µg/g in indoor dust. The levels of all pollutants, except Zn, in dust from the e-waste recycling area were significantly higher than those from the other areas. Cd, Pb, and most OCs exhibited similar pollution patterns in the three areas, indicating that e-waste recycling activities are the major pollution source. In contrast, Cu, Cr, Zn, and penta-BDE are likely derived from household products in the rural and urban areas. The highest estimated daily intakes (EDIs) of PCBs, PBDEs, DBDPE, and DPs were 0.15-163, 3.97-1470, 1.26-169, and 0.11-134ng/kg bw/day for toddlers and adults. The highest EDIs of BDE 209 and Pb in toddlers in the e-waste recycling area were 16% and 18 times higher than the reference doses, indicating the high exposure risk of these pollutants in the e-waste recycling area.

Comparative Transcriptome Analysis between Low- and High-Cadmium-Accumulating Genotypes of Pakchoi (Brassica chinensis L.) in Response to Cadmium Stress.

To reduce cadmium (Cd) pollution of food chains, screening and breeding of low-Cd-accumulating cultivars are the focus of much study. Two previously identified genotypes, a low-Cd-accumulating genotype (LAJK) and a high-Cd-accumulating genotype (HAJS) of pakchoi (Brassica chinesis L.), were stressed by Cd (12.5 µM) for 0 h (T0), 3 h (T3) and 24 h (T24). By comparative transcriptome analysis for root tissue, 3005 and 4343 differentially expressed genes (DEGs) were identified in LAJK at T3 (vs T0) and T24 (vs T3), respectively, whereas 8677 and 5081 DEGs were detected in HAJS. Gene expression pattern analysis suggested a delay of Cd responded transcriptional changes in LAJK compared to HAJS. DEG functional enrichments proposed genotype-specific biological processes coped with Cd stress. Cell wall biosynthesis and glutathione (GSH) metabolism were found to involve in Cd resistance in HAJS, whereas DNA repair and abscisic acid (ABA) signal transduction pathways played important roles in LAJK. Furthermore, the genes participating in Cd efflux such as PDR8 were overexpressed in LAJK, whereas those responsible for Cd transport such as YSL1 were more enhanced in HAJS, exhibiting different Cd transport processes between two genotypes. These novel findings should be useful for molecular assisted screening and breeding of low-Cd-accumulating genotypes for pakchoi.

Analysis of human hair to assess exposure to organophosphate flame retardants: Influence of hair segments and gender differences.

Hair is a promising, non-invasive, human biomonitoring matrix that can provide insight into retrospective and integral exposure to organic pollutants. In the present study, we measured the concentrations of organophosphate flame retardants (PFRs) in hair and serum samples from university students in Guangzhou, China, and compared the PFR concentrations in the female hair segments using paired distal (5~10cm from the root) and proximal (0~5cm from the root) samples. PFRs were not detected in the serum samples. All PFRs except tricresyl phosphate (TMPP) and tri-n-propyl phosphate (TPP) were detected in more than half of all hair samples. The concentrations of total PFRs varied from 10.1 to 604ng/g, with a median of 148ng/g. Tris(chloroisopropyl) phosphate (TCIPP) and tri(2-ethylexyl) phosphate (TEHP) were the predominant PFRs in hair. The concentrations of most PFRs in the distal segments were 1.5~8.6 times higher than those in the proximal segments of the hair (t-test, p<0.05), which may be due to the longer exposure time of the distal segments to external sources. The values of log (PFR concentrations-distal/PFR concentrations-proximal) were positively and significantly correlated with log KOA of PFRs (p<0.05, r=0.68), indicating that PFRs with a higher log KOA tend to accumulate in hair at a higher rate than PFRs with a lower log KOA. Using combined segments of female hair, significantly higher PFR concentrations were observed in female hair than in male hair. In contrast, female hair exhibited significantly lower PFR concentrations than male hair when using the same hair position for both genders (0-5cm from the scalp). The controversial results regarding gender differences in PFRs in hair highlight the importance of segmental analysis when using hair as an indicator of human exposure to PFRs.

Polybrominated Diphenyl Ethers (PBDEs) in paired human hair and serum from e-waste recycling workers: source apportionment of hair PBDEs and relationship between hair and serum.

Human hair has been widely used as a bioindicator for human persistent organic pollutants (POPs) exposure, but studies on the sources of hair POPs and the relationship between hair and body burden are limited. This study analyzed the possible source apportionment of hair PBDEs and examined the relationship between PBDE concentrations in paired hair and serum from e-waste recycling workers. Using the ratio of BDE 99/47 and BDE 209/207 as indices, we calculated that only 15% of the highly brominated congeners (nona- and deca-BDE congeners) comes from exogenous (external) exposure for both female and male hair, but an average of 64% and 55% of the lower-brominated congeners (tetra- to penta-BDE congeners) come from exogenous exposure for female and male hair, respectively. The higher contribution of exogenous exposure for less-brominated congeners could be related to their relatively lower log KOW and higher volatility than higher-brominated congeners, which make them more readily to evaporate from dust and then to be adsorbed on hair. Higher hair PBDE levels and higher exogenous exposure of less-brominated congeners in females than in males can be attributed to a longer exogenous exposure time for females than males. Significant positive relationships were found in tri- to hepta-BDE congeners (BDE 28, 47, 66, 85, 100, 153, 154, and 183) (R = 0.36-0.55, p < 0.05) between hair and serum, but this relationship was not found for octa- to deca-BDE. Difference in the half-lives between highly brominated congeners and less-brominated congeners could be a reason. This result also implied that we should treat the results of correlation analyses between hair and other organs cautiously.

Phytochelatin-Mediated Cultivar-Dependent Cd Accumulations of Lactuca sativa and Implication for Cd Pollution-Safe Cultivars Screening.

Cd pollution-safe cultivar (Cd-PSC) is a feasible strategy to minimize Cd contamination in leafy vegetables. The shoot Cd concentrations of 23 Lactuca sativa cultivars under Cd stress ranged from 0.124 to 2.155 mg·kg-1 with a maximum cultivar difference of 8 folds. Typical Cd-PSC C16 (L) and high-Cd-accumulating cultivar C13 (H) were screened to investigate the mechanisms of Cd accumulations in L. sativa through determining Cd concentrations, Cd subcellular distributions, phytochelatin profiles, and phytochelatin biosynthesis-related genes' expressions. Higher Cd distribution in a heat stable fraction in C13 (H) indicated that the high Cd accumulation trait of C13 (H) mainly depended on the Cd-phytochelatin complexes. Root phytochelatin concentrations were significantly elevated in C13 (H) (5.83 folds) than in C16 (L) (2.69 folds) (p < 0.05) under Cd stress. Significantly downregulated expressions of glutathione S-transferase rather than the regulation of phytochelatin synthesis genes in the root of C13 (H) might be responsible for sufficient glutathione supply for phytochelatins synthesis. These findings suggested that phytochelatin elevation in C13 (H) would favor the Cd root to shoot transportation, which provides new insights into the phytochelatin-related cultivar-dependent Cd accumulating characteristic in L. sativa.

Proteomic and Biochemical Evidence Involving Root Cell Wall Biosynthesis and Modification, Tricarboxylic Acid Cycle, and Glutathione Metabolism in Cultivar-Dependent Cd Accumulation of Water Spinach (Ipomoea aquatica).

Proteomic analysis and biochemical tests were employed to investigate the critical biological processes responsible for the different cadmium (Cd) accumulations between two water spinach (Ipomoea aquatica) cultivars, QLQ and T308. QLQ, with lower shoot Cd accumulation and translocation factor than T308, possessed higher expression of cell wall biosynthesis and modification proteins in roots, together with higher lignin and pectin contents, higher pectin methylesterase activity, and lower pectin methylation. The results demonstrated that QLQ could more effectively restrict root-to-shoot Cd translocation by compartmentalizing more Cd in root cell walls. In contrast, T308 showed higher expression of the tricarboxylic acid (TCA) cycle, glutathione (GSH) metabolism, and heavy metal transporter proteins, accompanied by higher GSH content and glutathione S-transferase (GST) and glutathione reductase (GR) activity, which accelerated Cd uptake and translocation in T308. These findings revealed several critical biological processes responsible for cultivar-dependent Cd accumulation in water spinach, which are important for elucidating Cd accumulation and transport mechanisms in different cultivars.

A novel microRNA IamiR-4-3p from water spinach (Ipomoea aquatica Forsk.) increased Cd uptake and translocation in Arabidopsis thaliana.

MicroRNAs (miRNAs) play important roles in plant response to Cd stress. In our previous study, we observed significant differences in the expression levels of IamiR-4-3p between high-Cd and low-Cd cultivars of water spinach. The function of IamiR-4-3p was investigated by using wild type Arabidopsis (WT), Arabidopsis transfected with empty vector pCambia1302 (CK), and Arabidopsis transfected with IamiR-4-3p + vector pCambia1302 (p35S::miR-4-3p) in this study. In p35S::miR-4-3p Arabidopsis, the expression levels of GST3 and AWPM19-like were reduced by 20% and 24%. Under Cd treatment, higher root and shoot Cd concentrations were detected in the transgenic p35S::miR-4-3p Arabidopsis. MDA and H2O2 concentrations were positively correlated with the Cd concentrations in all Arabidopsis. The elevated GSH pool in p35S::miR-4-3p Arabidopsis should compensate for its restricted GST3 expression in response to Cd-induced oxidative stress. Lower F1 (cell wall) and higher F2 (organelle) and F3 (soluble fraction) Cd concentrations were observed along with the reduced ABA level in p35S::miR-4-3p Arabidopsis, which could induce a weakened apoplastic barrier and higher Cd accumulation and translocation in roots. It is suggested that IamiR-4-3p is able to reduce the expression levels of GST3 and AWPM19-like, resulting in higher Cd uptake and translocation in Arabidopsis.

The enantiomer-selective metabolism of hexabromocyclododecanes (HBCDs) by human HepG2 cells.

Although hepatic metabolism of hexabromocyclododecanes (HBCDs) played critical roles in the selective bioaccumulation of HBCDs in humans, the hepatic metabolism patterns of its enantiomers remained ambiguous. Aiming to elucidate the mechanism on hepatic metabolism of hexabromocyclododecanes (HBCDs) enantiomers, the enantiomers ((+)-α-HBCD, (-)-α-HBCD, (+)-γ-HBCD, and (-)-γ-HBCD), the diastereoisomers (α-, ß-, and γ-HBCDs) and the mixed of α- and γ-HBCDs were incubated with human HepG2 cell under different exposure levels in the present study. The clearance percentages ranked as γ-HBCD enantiomers >ß-HBCD enantiomers >α-HBCD enantiomers at the same exposure levels. The clearance percentages of (+)- and (-)-α-HBCDs increased when cells were exposed to racemic α-HBCD and the mixture of racemic α- and γ-HBCDs (p < 0.05). (-)-γ-HBCD was more resistant to human hepatic metabolism than (+)-γ-HBCD, leading to the enantiomer fractions (EFs) of γ-HBCD lower than 0.50. (-)-α-HBCD was slightly more metabolized when independently exposed to α-HBCD, while (+)-α-HBCD was more preferentially metabolized after exposure to α- and γ-HBCD mixtures. Hydroxylation and debromination HBCD metabolites were identified. In addition, the different EFs of HBCDs in cells and mediums suggested the selective transfer of chiral HBCDs and HBCD metabolites through the cell membrane. This study provided new insight into the enantiomer-selective metabolism of HBCDs.

Lignin side chain region participates in Cd detoxification related to the cultivar-dependent Cd accumulation in Brassica chinensis L.

To investigate the effect of lignin in the cultivar-dependent Cd detoxification of Brassica chinensis L., Cd and lignin contents, lignin composition and laccase genes expressions in low-Cd-accumulating (LAJK) and high-Cd-accumulating (HAJS) cultivars grown under control (CK) and 25 µM Cd-treatment were determined. The results showed that lignin combined about 14 % of total Cd in both LAJK and HAJS. LAC genes were more up-regulated in HAJS than in LAJK, indicating that the LAC genes were involved in the cultivar-dependent lignin functions. Higher ß-aryl ether (A) proportion in the lignin side chain region in LAJK than in HAJS were observed, whereas resinol (B) and phenylcoumaran (C) constitute much higher proportions in HAJS than in LAJK. Chemical calculation to estimate Cd affinity associating with lignin side chain region displayed that i) ß-aryl ether (A) exhibited major coupling with lignin aromatic region; ii) resinol (B) and phenylcoumaran (C) displayed major participation in complexation with Cd. We therefore conclude that Cd compartmentalization in the secondary cell wall (SCW) by coupling with lignin side chain region is responsible for Cd detoxification related to cultivar-dependent Cd accumulation of Brassica chinensis. This is the first study on lignin composition in relation to Cd retention mechanisms in SCW.

Comparative Transcriptome Analysis Revealed the Tissue-Specific Accumulations of Taxanes among Three Experimental Lines of Taxus yunnanensis.

Taxus yunnanensis (Yew) is known for natural anticancer metabolite paclitaxel (Taxol) and its biosynthesis pathway in yew species still needs to be completely elucidated. In the current study, productions of paclitaxel and 10-DAB III from three different tissues (needle, branch, and root) of T. yunnanensis wild type (WT) and two new cultivars Zhongda-1 (Zd1) and Zhongda-2 (Zd2) were determined, and significant tissue differences in contents of the taxanes were observed among the three experimental lines. The much higher 10-DAB III and lower paclitaxel contents in needle of Zd2 when compared with that of Zd1 indicated the low conversion from 10-DAB III to paclitaxel in the needle of Zd2. In order to uncover the mechanisms of the tissue-specific biosynthesis of the taxanes, transcriptome analysis of cultivar Zd2 was conducted, and the previously reported transcriptome data of Zd1 and WT were used to perform a comparison. The enhancement of TDAT and T10ßH side biosynthetic pathway in roots of Zd2 in early taxane synthesis might lead to the biosynthesis of other toxoids, while the preference of T13αH route in the needle and branch of Zd2 was mainly responsible for the tissue-specific reinforced biosynthesis of 10-DAB III and paclitaxel in Zd2. Different from Zd1, the tissue-specific pattern of paclitaxel biosynthesis genes in Zd2 was similar to WT. However, the lower transcript abundance of final steps genes (TBT, DBAT, BAPT, and DBTNBT) of the paclitaxel biosynthesis pathway in Zd2 than in Zd1 might further promote 10-DAB III accumulation in Zd2.

Different Proteomic Processes Related to the Cultivar-Dependent Cadmium Accumulation of Amaranthus gangeticus.

To deal with the Cd contaminant of agricultural soil, pollution-safe cultivar (PSC) is developed to minimize the Cd accumulation risk in crops. The present study aimed to investigate the different proteomic responses related to Cd accumulation in different tissues between two Amaranthus gangeticus cultivars, Pen and Nan. A significantly higher Cd accumulation in Pen than in Nan was unraveled, especially in shoot. The proportions of soluble Cd in root and stem of Nan were significantly lower than those of Pen, implying lower Cd transportation from root to shoot in Nan. Higher contents of NaCl-extracted Cd in Pen than in Nan were probably attributed to the enhancement of GSH related metabolism in Pen, which activated the transportation of Cd from root to shoot. Alteration of other proteins involved in Cd detoxification and energy production also demonstrated that Pen had exhibited a stronger tolerance than Nan in dealing with Cd stress. Thus, differences in the proteomic processes associated with biochemical differences between the two typical cultivars suggested a cultivar-dependent capacity of Cd tolerance and accumulation in amaranth for the first time.

Cadmium and lead accumulations and agronomic quality of a newly bred pollution-safe cultivar (PSC) of water spinach.

Breeding for pollution-safe cultivars (PSCs) can reduce pollutant accumulation in crops. However, the PSC breeding would face the risk of nutritional quality reduction, which is usually ignored in conventional breeding programs targeting to increase crop yield or nutritional quality. Thus, the doubt whether the risk would exist has to be clarified for supporting the PSC breeding. In the present study, a newly bred Cd/Pb-PSC of water spinach (Ipomoea aquatic Forsk.) and its parents (QLQ with low-Cd/Pb accumulation ability and T308 with high yield) of water spinach were employed to clarify the above-mentioned issue. Yields, and concentrations of Cd, Pb, nitrite, and organic and inorganic nutrients in shoots of the three experimental lines were determined. There were no significant differences in Cd/Pb concentration between the new PSC and QLQ, in nitrite content between the new PSC and its two parents and in yield between the new PSC and T308. It is decisively significant that shoot concentrations of organic and inorganic nutrients in the Cd/Pb-PSC were as high as those in one of its parents. It is affirmed that the breeding operations (crossing and consequently continuous selfing) for lowering Cd/Pb accumulation capacity of water spinach would not lower the nutritional values of the obtained Cd/Pb-PSCs from the breeding, which should be a pillar that supports the feasibility to minimize Cd/Pb pollution in vegetables using PSC-breeding method.

Transcriptome profiling reveals specific patterns of paclitaxel synthesis in a new Taxus yunnanensis cultivar.

The difference in contents of paclitaxel and 10-deacetylbaccatin III (10-DABIII) in needles between wildtype (WT) and a new cultivar (Zhongdayihao, ZD1) of Taxus yunnanensis was examined. Transcriptome profiling was conducted for different tissues of the ZD1 and WT to illustrate the regulation mechanism of paclitaxel biosynthesis. It was observed that average contents of paclitaxel and 10-DABIII in ZD1 were 4 folds and 32 folds higher than those in WT, respectively. More significant elevations of differential expressed genes (DEGs) from paclitaxel biosynthesis pathway were revealed in ZD1 rather than WT, which should be responsible for the higher contents of paclitaxel and 10-DABIII in the ZD1. Special tissues-dependent expression patterns of paclitaxel biosynthesis DEGs in ZD1 compared to WT were unraveled. The relative higher expressions of paclitaxel biosynthesis genes in needles than other tissues supported the higher content of paclitaxel and 10-DABIII content in needles of ZD1. Attenuation of plant hormone signal transduction pathway led to the lower expression of TFs in ZD1 rather than WT. Besides, the significant negative correlations between differential expressed TFs and DEGs from paclitaxel biosynthesis pathway displayed a possibly negative regulation pattern of these TFs on paclitaxel biosynthesis pathway genes. These results provided new insights into the molecular process of paclitaxel synthesis in Taxus.

Disruption of thyroid hormone (TH) levels and TH-regulated gene expression by polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and hydroxylated PCBs in e-waste recycling workers.

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) are the primary toxicants released by electronic waste (e-waste) recycling, but their adverse effects on people working in e-waste recycling or living near e-waste sites have not been studied well. In the present study, the serum concentrations of PBDEs, PCBs, and hydroxylated PCBs, the circulating levels of thyroid hormones (THs), and the mRNA levels of seven TH-regulated genes in peripheral blood leukocytes of e-waste recycling workers were analyzed. The associations of the hormone levels and gene expression with the exposure to these contaminants were examined using multiple linear regression models. There were nearly no associations of the TH levels with PCBs and hydroxylated PCBs, whereas elevated hormone (T4 and T3) levels were associated with certain lower-brominated BDEs. While not statistically significant, we did observe a negative association between highly brominated PBDE congeners and thyroid-stimulating hormone (TSH) levels in the e-waste workers. The TH-regulated gene expression was more significantly associated with the organohalogen compounds (OHCs) than the TH levels in these workers. The TH-regulated gene expression was significantly associated with certain PCB and hydroxylated PCB congeners. However, the expression of most target genes was suppressed by PBDEs (mostly highly brominated congeners). This is the first evidence of alterations in TH-regulated gene expression in humans exposed to OHCs. Our findings indicated that OHCs may interfere with TH signaling and/or exert TH-like effects, leading to alterations in related gene expression in humans. Further research is needed to investigate the mechanisms of action and associated biological consequences of the gene expression disruption by OHCs.

Comparative analysis of cadmium responsive microRNAs in roots of two Ipomoea aquatica Forsk. cultivars with different cadmium accumulation capacities.

In plants, microRNAs (miRNAs) play regulatory roles in response to various environmental stresses. In order to illustrate the regulation mechanisms of miRNAs involving the different Cd accumulation abilities between a low-shoot-Cd cultivar (QLQ) and a high-shoot-Cd cultivar (T308) of water spinach (Ipomoea aquatic Forsk.), six sRNA libraries at 3 different time points were constructed. Only 5 miRNAs were exclusively regulated in QLQ, among them, miRNA395 was up-regulated, which was supposed to enhance the Cd retention and detoxification in root. Also, the alterations of miRNA5139, miRNA1511 and miRNA8155 contributed to the attenuation of Cd translocation into the shoot of QLQ. More differentially expressed miRNAs were observed in T308, indicating more complex response was adopted by T308 under Cd stress. miRNA397 exclusively regulated in T308 has enhanced the Cd influx of T308 under Cd treatments. Besides, the Cd translocation of T308 was strengthened due to the up-regulation of MATE efflux family, which was targeted by miRNA3627. Our results unraveled the effects of the cultivar-dependent expression of these specific miRNAs on the different Cd accumulation and translocation abilities of QLQ and T308. These findings provide a new perspective for the molecular assisted breeding of low-Cd cultivars for leaf-vegetables.

Comparative Transcriptome Analysis of Two Ipomoea aquatica Forsk. Cultivars Targeted To Explore Possible Mechanism of Genotype-Dependent Accumulation of Cadmium.

A low-shoot-Cd (QLQ) and a high-shoot-Cd cultivar (T308) of water spinach (Ipomoea aquatica Forsk.) were used to investigate molecular mechanism of the genotype difference in cadmium (Cd) accumulation. RNA-Seq under 9 and 72 h cadmium exposures (5 mg L(-1)) were undertaken to explore Cd induced genotype differences in molecular processes. In total, 253 747 540 clean reads were assembled into 57 524 unigenes. Among them, 6136 and 10 064 unigenes were differentially expressed in QLQ and T308, respectively. Cell wall biosynthesis genes, such as GAUT and laccase, and three Cd efflux genes (Nramp5, MATE9, and YSL7) had higher expression levels in QLQ, while the genes in sulfur and glutathione metabolism pathway, e.g., sulfate transporter and cysteine synthase, showed higher expression levels in T308. These findings would be useful for further understanding of the mechanisms related to genotype-dependent Cd accumulation and developing the molecular assisted screening and breeding of low-shoot-Cd cultivars for water spinach.

Occurrence of organophosphorus flame retardants in indoor dust in multiple microenvironments of southern China and implications for human exposure.

Organophosphorus flame retardants (OPFRs) are important alternatives to brominated flame retardants (BFRs), but information on their contamination of the environment in China is rare. We examined the occurrence of 12 OPFRs in indoor dust in four microenvironments of southern China, including a rural electronic waste (e-waste) recycling area, a rural non-e-waste area, urban homes, and urban college dormitory rooms. The OPFR concentrations (with a median of 25.0 µg g(-1)) were highest in the e-waste area, and the concentrations in other three areas were lower and comparable (7.48-11.0 µg g(-1)). The levels of OPFRs in the present study were generally relatively lower than the levels of OPFRs found in Europe, Canada, and Japan because BFRs are still widely used as the major FRs in China. The composition profile of OPFRs in the e-waste area was dominated by tricresyl phosphate (TCP) (accounting for 40.7%, on average), while tris(2-chloroethyl) phosphate (TCEP) was the most abundant OPFR (64.4%) in the urban areas (homes and college dormitories). These two distribution patterns represent two OPFR sources (i.e., emissions from past e-waste and from current household products and building materials). The difference in the OPFR profiles in the rural area relative to the OPFR profiles in the urban and e-waste areas suggests that the occurrence of OPFRs is due mainly to emissions from characteristic household products in rural homes. Although human exposures to all the OPFRs were under the reference doses, the health risk for residents in the e-waste area is a concern, considering the poor sanitary conditions in this area and exposure from other sources.