Tolerance To Cd Stress Research Articles

Phosphorus influence Cd phytoextraction in Populus stems via modulating xylem development, cell wall Cd storage and antioxidant defense.

The soils in mining lands with cadmium (Cd) contamination usually are deficient in nutrients. Disclosing how P nutrition and N:P stoichiometric ratio influences Cd accumulation and stress tolerance in stems of Populus spp. will facilitate the phytoremediation of mining sites polluted by Cd. In this study, investigations at the anatomical and physiological levels were conducted using a clone of Populus× euramericana. Both phosphorus deficiency and cadmium exposure inhibited xylem development via reducing cell layers in the xylem. Under P-sufficient condition, appropriate P status and balanced N:P ratio in stem promoted xylem development under Cd exposure via stimulating cell division, which enhanced Cd accumulation in stems. Cd accumulation in cell walls of collenchyma tissues of the stem was enhanced by P application due to increased polysaccharide production and cell wall affinity for Cd. The low P concentrations (0.3-0.4 mg g-1) and imbalanced N:P ratio under P deficiency inhibited the production of APX and ascorbate-GSH cycle, which increased oxidative stress and lipid peroxidation as indicated by high MDA concentration in stem. Under P-sufficient condition, the interactions between phytohormones and antioxidants play crucial roles in the process of antioxidant defense under Cd exposure. In conclusions, appropriate P addition and balanced N:P ratio enhanced secondary xylem development and promoted cadmium accumulation and stress tolerance in Populus stems, which can benefit the phytoextraction of Cd from Cd-contaminated soil.

Negative regulation of cadmium tolerance in Arabidopsis by MMDH2.

MMDH2 gene negatively regulates Cd tolerance by modulating reactive oxygen species (ROS) levels and the ROS-mediated signaling, thus, affecting the expression of PDR8. The molecular mechanism by which plants respond to stress caused by cadmium (Cd), one of the most toxic heavy metals to plants, is not well understood. Here, we show that MMDH2, a gene encoding mitochondrial malate dehydrogenase, is involved in Cd stress tolerance in Arabidopsis. The expression of MMDH2 was repressed by Cd stress. The mmdh2 knockdown mutants showed enhanced Cd tolerance, while the MMDH2-overexpressing lines were sensitive to Cd. Under normal and Cd stress conditions, lower H2O2 levels were detected in mmdh2 mutant plants than in wild-type plants. In contrast, higher H2O2 levels were found in MMDH2-overexpressing lines, and they were negatively correlated with malondialdehyde levels. In addition, the expression of the PDR8, a gene encoding a Cd efflux pump, increased and decreased in the mmdh2 mutant and MMDH2-overexpressing lines, in association with lower and higher Cd concentrations, respectively. These results suggest that the MMDH2 gene negatively regulates Cd tolerance by modulating reactive oxygen species (ROS) levels and the ROS-mediated signaling, thus, affecting the expression of PDR8.

Comparative Transcriptome Profiling Under Cadmium Stress Reveals the Uptake and Tolerance Mechanism in Brassica juncea

Cadmium (Cd) is a biologically non-essential and phytotoxic heavy metal pollutant. In this study, we estimated the Cd accumulation potential of Indian mustard and identified factors responsible for Cd uptake, tolerance, and detoxification. Eight transcriptomic libraries were sequenced and ≈ 230 million good quality reads were generated. The alignment rate against B. juncea reference genome V1.5 varied in the range of 85.03–90.06%. Comparative expression analysis using DESeq2 revealed 11,294 genes to be significantly differentially expressed under Cd treatment. The agriGO singular enrichment analysis revealed genes related to response to chemical, oxidative stress, transport, and secondary metabolic process were upregulated, whereas multicellular organismal development, developmental process, and photosynthesis were downregulated by Cd treatment. Furthermore, 616 membrane transport proteins were found to be significantly differentially expressed. Cd-related transporters such as metal transporter (Nramp1), metal tolerance protein (MTPC2, MTP11), cadmium-transporting ATPase, and plant cadmium resistance protein (PCR2, PCR6) were upregulated whereas cadmium/zinc-transporting ATPase (HMA2, HMA3, HMA4), high-affinity calcium antiporter (CAX1), and iron transport protein (IRT1) were downregulated by Cd treatment. A total of 332 different gene-networks affected by Cd stress were identified using KAAS analysis. Various plant hormones signaling cascades were modulated suggesting their role in Cd stress tolerance. The regulation overview using MapMan analysis also revealed gene expression related to plant hormones, calcium regulation, and MAP kinases were altered under Cd stress.

The miRNAome of ramie (Boehmeria nivea L.): identification, expression, and potential roles of novel microRNAs in regulation of cadmium stress response

BackgroundMicroRNAs (miRNAs) regulate numerous crucial abiotic stress processes in plants. However, information is limited on their involvement in cadmium (Cd) stress response and tolerance mechanisms in plants, including ramie (Boehmeria nivea L.) that produces a number of economic valuable as an important natural fibre crop and an ideal crop for Cd pollution remediation.ResultsFour small RNA libraries of Cd-stressed and non-stressed leaves and roots of ramie were constructed. Using small RNA-sequencing, 73 novel miRNAs were identified. Genome-wide expression analysis revealed that a set of miRNAs was differentially regulated in response to Cd stress. In silico target prediction identified 426 potential miRNA targets that include several uptake or transport factors for heavy metal ions. The reliability of small RNA sequencing and the relationship between the expression levels of miRNAs and their target genes were confirmed by quantitative PCR (q-PCR). We showed that the expression patterns of miRNAs obtained by q-PCR were consistent with those obtained from small RNA sequencing. Moreover, we demonstrated that the expression of six randomly selected target genes was inversely related to that of their corresponding miRNAs, indicating that the miRNAs regulate Cd stress response in ramie.ConclusionsThis study enriches the number of Cd-responsive miRNAs and lays a foundation for the elucidation of the miRNA-mediated regulatory mechanism in ramie during Cd stress.

The remediation potential and kinetics of cadmium in the green alga Cladophora rupestris.

This study determined the subcellular distribution, chemical forms, and effects of metal homeostasis of excess Cd in Cladophora rupestris. Biosorption data were analyzed with Langmuir and Freundlich adsorption models and kinetic equations. Results showed that C. rupestris can accumulate Cd. Cd mainly localized in the cell wall and debris (42.8-68.2%) of C. rupestris, followed by the soluble fraction (22.1-38.4%) observed in C. rupestris. A large quantity of Cd ions existed as insoluble CdHPO4 complexed with organic acids, Cd(H2PO4)2, Cd-phosphate complexes (FHAC) (43.2-56.0%), and pectate and protein-integrated Cd (FNaCl) (30.8-43.2%). The adsorption data were well fitted by the Freundlich model (R2 = 0.933) and could be described by the pseudo-second-order reaction rate (R2 = 0.997) and Elovich (R2 = 0.972) equations. Related parameters indicated that Cd adsorption by C. rupestris is a heterogeneous diffusion. Cd promoted Ca and Zn uptake by C. rupestris. Cu, Fe, Mn, and Mg adsorption was promoted by low Cd concentrations and inhibited by high Cd concentrations. Results suggested that cell wall sequestration, vacuolar compartmentalization, and chemical morphological transformation are important mechanisms of Cd stress tolerance by C. rupestris. This study suggests that C. rupestris has bioremediation potential of Cd.

Methyl Jasmonate and Nitrogen Interact to Alleviate Cadmium Stress in Mentha arvensis by Regulating Physio-Biochemical Damages and ROS Detoxification

We examined effects of methyl jasmonate (MeJ), with and without N, for the alleviation of the adverse effects of 150 mg kg−1 CdCl2 stress in mentholmint (Mentha arvensis) plants. Exposure of mentholmint plants to Cd stress reduced morphological growth parameters, photosynthetic attributes, chlorophyll content and mineral nutrient assimilation rate. Cd stress significantly increased endogenous leaf and root Cd content by 67.10% and 83.05%, respectively, electrolyte leakage by 67.26%, hydrogen peroxide (H2O2) by 56.66% and malondialdehyde content by 53.97% over that of the control. Cd stress upregulated activities of antioxidant enzymes and increased osmolyte concentration. Application of 1 µM MeJ to Cd-stressed plants partially alleviated the Cd-induced oxidative stress; however, co-application of MeJ with inorganic N reversed the detrimental effects more than did MeJ or N alone. Combined application of MeJ + N further elevated the osmolyte levels and markedly increased mineral nutrient contents and nitrogen use efficiency. MeJ + N significantly reduced the production of reactive oxygen species (ROS) directly or indirectly through higher stimulation of ROS-scavenging enzymes and decreased the root-to-shoot Cd rate of translocation. Cd-induced stomatal inhibition was recovered by MeJ and N. Our study demonstrated the regulatory role of MeJ and N in overcoming Cd stress in mentholmint plants. The study is the first report of regulatory interaction of the exogenous phytohormone (MeJ) with inorganic nutrient (N) for enhancing Cd stress tolerance in mentholmint plants, the same concept can be used for remediation of toxic metal/metalloids in agricultural production.

The defensive role of silicon in wheat against stress conditions induced by drought, salinity or cadmium

In the crust of earth, silicon (Si) is one of the two major elements. For plant growth and development, importance of Si remains controversial due to the widely differences in ability of plants to take up this element. In this paper, pot experiments were done to study Si roles in improving salt, drought or cadmium (Cd) stress tolerance in wheat. Up to full emergence, all pots were watered at 100% field capacity (FC) every other day with nutrient solution without any treatments. Fifteen days after sowing, pots were divided into four plots, each with 40 pots for no stress (control) and three stress treatments; drought (50% FC), salinity (200 mM NaCl) and cadmium (2 mM Cd). For all plots, Si was applied at four levels (0, 2, 4 and 6 mM). Under no stress condition, Si applications increased Si content and improved growth as a result of reduced electrolyte leakage (EL), malondialdehyde (MDA) and Na+ contents. Under stress conditions, Si supplementation conferred higher growth, gas exchange, tissue water and membranes stabilities, and K+ content, and had limited MDA and Na+ contents and EL compared to those obtained without Si. Compared to those without Si, enzyme (e.g., superoxide dismutase, catalase and peroxidase) activity was improved by Si applications, which were linked with elevated antioxidants and osmoprotectants (e.g., free proline, soluble sugars, ascorbic acid and glutathione) contents, might providing antioxidant defense against abiotic stress in wheat. The level of 4 mM Si was most effective for mitigating the salt and drought stress conditions, while 6 mM Si level was most influentially for alleviating the Cd stress condition. These results suggest that Si is beneficial in remarkably affecting physiological phenomena and improving wheat growth under abiotic stress.

Interactive effects of aluminum and cadmium on phenolic compounds, antioxidant enzyme activity and oxidative stress in blueberry (Vaccinium corymbosum L.) plantlets cultivated in vitro

To evaluate the potential role of phenolic compounds in Al and Cd stress tolerance mechanisms, Vaccinium corymbosum cv. Legacy plantlets were exposed to different metal concentrations. The present study used an in vitro plant model to test the effects of the following treatments: 100μM Al; 100μMAl + 50μMCd; and 100μMAl + 100μMCd during periods of 7, 14, 21 and 30 days. The oxidative damage was determined by the accumulation of malondialdehyde (MDA) and hydrogen peroxide (H2O2). The antioxidant activity values were determined using 1,1-diphenyl-2-picrylhydrazine (DPPH) and the ferric reducing antioxidant power test (FRAP). Additionally, the phenolic compound concentrations were determined using HPLC-DAD. The exposure to Al and Cd increased the MDA and H2O2 contents differentially, while the antioxidant capacity values showed differences between DPPH and FRAP with the largest changes in FRAP relative to Cd. SOD had the highest activity in the first 7 days, leading to a significant increase in phenolic compounds observed after 14 days, and chlorogenic acid was the major compound identified. Our results revealed that phenolic compounds seem to play an important role in the response to ROS. Therefore, the mechanisms of tolerance to Al and Cd in V. corymbosum will be determined by the type of metal and time of exposure.

A novel aldo-keto reductase gene, IbAKR, from sweet potato confers higher tolerance to cadmium stress in tobacco

High concentrations of Cd can inhibit growth and reduce the activity of the photosynthetic apparatus in plants. In several plant species, aldo-keto reductases (AKRs) have been shown to enhance tolerance to various abiotic stresses by scavenging cytotoxic aldehydes; however, few AKRs have been reported to enhance Cd stress tolerance. In this study, the gene <i>IbAKR</i> was isolated from sweet potato. The relative expression levels of <i>IbAKR</i> increased significantly (approximately 3-fold) after exposure to 200 <font style="font-family:Symbol">m</font>mol·L⁻¹ CdCl₂ or 10 mmol·L⁻¹ H₂O₂. A subcellular localization assay showed that <i>IbAKR</i> is predominantly located in the nucleus and cytoplasm. <i>IbAKR</i>-overexpressing tobacco plants showed higher tolerance to Cd stress than wild-type (WT). Transgenic lines showed a significant ability to scavenge malondialdehyde (MDA) and methylglyoxal (MG). In addition, proline content and superoxide dismutase activity were significantly higher and H₂O₂ levels were significantly lower in the transgenic plants than in the WT. Quantitative real-time PCR analysis showed that the reactive oxygen species (ROS) scavenging genes encoding guaiacol peroxidase (<i>GPX</i>), ascorbate peroxidase (<i>APX</i>), monodehydroascorbate reductase (<i>MDHAR</i>) and peroxidase (<i>POD</i>) were significantly upregulated in transgenic plants compared to WT under Cd stress. These findings suggest that overexpressing <i>IbAKR</i> enhances tolerance to Cd stress via the scavenging of cytotoxic aldehydes and the activation of the ROS scavenging system.

The role of phytochromes in cadmium stress responses in tomato

ABSTRACT It is well known that phytochromes mediate a wide range of photomorphogenic processes in plants. In addition, many studies have demonstrated the involvement of phytochromes as part of abiotic stress signaling responses. However, little is known about cadmium (Cd) stress regulation by phytochromes. Thus, in this study, we used the phyA (far red-insensitive; fri), phyB1 (temporary redinsensitive; tri) and phyB2 (phyB2) tomato (Solanum lycopersicum L.) mutants to investigate the roles of these three phytochromes on Cd stress responses. The plants were grown over a 21-d period in the presence of Cd. We evaluated plant growth, Cd and chlorophyll content and anatomical changes in the leaves. The results indicated that all genotypes were affected by Cd and showed reduced growth of the shoots and roots, as well as reduced chlorophyll content. The accumulation of Cd was similar for all genotypes, and a higher Cd content was found in roots. Anatomical analysis of the vascular bundles revealed that fri and tri seem to be more disrupted by Cd. Overall, these results indicate that phytochromes do not determine Cd stress tolerance in tomato plants.

Unravelling cadmium toxicity and nitric oxide induced tolerance in Cucumis sativus: Insight into regulatory mechanisms using proteomics

Nitric oxide (NO) is a signal molecule that can mediate a wide range of physiological processes against cadmium (Cd) toxicity in plants. However, little information can be used to reveal the global and systematic mitigative mechanism of NO in improving Cd stress tolerance of cucumber plants. In the present study, we used Isobaric Tag for Relative and Absolute Quantification (iTRAQ) analysis to identify 1691 proteins, which can be used to determine the role of NO in regulating the molecular changes of proteome in cucumber leaves exposed to Cd stress. Several dysregulated key proteins indicated that Cd-induced physiological deterioration of cucumber leaves were mainly involved in metabolic process, cellular process, response to stimulus and so on. Metabolic pathway analysis indicated that several Cd-disruptive pathways were markedly reversed by NO treatments, including Cd transport and localization, photosynthesis, chlorophyll metabolism, redox homeostasis, glutathione-mediated Cd detoxification and Ca2+ signaling transduction. Taken together, this iTRAQ analysis provides more comprehensive insights into the physiological and molecular mechanisms of NO against Cd toxicity in cucumber plants.

Genetic variation in cadmium tolerance is related to transport and antioxidant activities in field peas (Pisum sativum L.)

ABSTRACTThis study elucidates mechanisms conferring differential tolerance to cadmium (Cd) stress in contrasting pea genotypes. Cd stress caused a significant decline in morphophysiological traits in Hurst Green Shaft but not in Kelvedon Wonder, suggesting that Cd-stress tolerance does exist in Kelvedon Wonder. Results showed a significant increase of Cd in roots of both genotypes but not in leaves of Kelvedon Wonder due to Cd stress. Consistently, RIT1 (Fe transporter) transcript showed downregulation and upregulation in Kelvedon Wonder and Hurst Green Shaft, respectively, in leaves upon Cd exposure. This consistent atomic absorption spectroscopy and expression data suggest that limiting Cd translocation by decreased RIT1 expression is related to the ability of Kelvedon Wonder plants to cope with Cd stress. Furthermore, an enhanced antioxidant activity was only observed in leaves of Kelvedon Wonder under Cd stress. Finally, high-performance liquid chromatography analysis showed elevated cysteine, methionine and glutathione in leaves of Kelvedon Wonder, suggesting better protection of pea plants from Cd-induced oxidative stress. Our findings reveal that differential tolerance to Cd stress is mainly attributed to Cd translocation and antioxidant defense in pea plants, which can be further implemented for Cd-free transgenic peas to limit environmental toxicity and health hazards.

English

In vitro cultures of plants offer a useful tool to study the adaptive mechanisms of plants in the presence of high metal concentrations. Callus cultures of tetraploid (Durum-97) and hexaploid (Shafaq-06) wheat genotypes exposed to different cadmium (Cd) concentrations (0, 100, 400, 800 and 1200 μM) and its alleviation by salicylic acid (0, 0.5 mM) were assayed for growth, antioxidant responses and Cd accumulation characters. Cadmium hampered the growth and notably enhanced antioxidant activity in all Cd regimes. We provided evidence that the two genotypes hexaploid and tetraploid are characterized by different response to cellular homeostasis and detoxification to Cd in callus culture. In particular, the high tolerance in hexploid genotype (Shafaq-06) is associated with relatively higher activity of antioxidants and Cd accumulation behaviour as indicated by Cd contents, bioconcentration factor (BCF) and stress tolerance index (STI). However, the follow-up treatment (0.5 mM) with salicylic acid (SA) mitigated the Cd generated stress and significantly (P≤0.05) improved the aforesaid parameters. © 2016 Friends Science Publishers

MicroRNA390 Is Involved in Cadmium Tolerance and Accumulation in Rice.

Cadmium (Cd) is a non-essential heavy metal that is toxic to plants. microRNAs (miRNAs) are 21-nucleotide RNAs that are ubiquitous regulators of gene expression at the post-transcriptional level. Several plant miRNAs, such as miR390, have vital roles in plant growth, development and responses to environmental stresses including heavy metal stress. In this study, the expression of mature miR390 was significantly down-regulated under Cd stress in rice. Consequently, the target gene of miR390, OsSRK was dramatically induced by Cd treatment. Transgenic rice plants overexpressing miR390 displayed reduced Cd tolerance and higher Cd accumulation compared with wild-type plants. Simultaneously, expression of OsSRK was less pronounced in 35S:MIR390 plants than in wild-type. These results indicate that miR390 was a negative regulator involved in Cd stress tolerance in rice.

Effects of exogenous calcium and spermidine on cadmium stress moderation and metal accumulation in Boehmeria nivea (L.) Gaudich.

Cadmium (Cd) is a detrimental metal in the environment and it is easily taken up by plants, thus entering the food chain and posing a severe threat to human health. Phytoremediation being low cost, highly stable, and environmentally friendly has been considered as a promising green technology for Cd remediation. The addition of exogenous substances to the culture media has been recognized as an efficient strategy to improve plant phytoremediation capability. Pot trials were conducted to investigate the combined effects of exogenous calcium (Ca) and spermidine (Spd) on Cd-induced toxicity in Boehmeria nivea (L.) Gaudich. (ramie). Results showed that the application of 5-mM exogenous Ca significantly alleviated Cd toxicity in ramie by reducing Cd accumulation, depressing H2O2 and malondialdehyde contents, increasing plants dry weights and chlorophyll concentrations, as well as altering the activities of total superoxide dismutase and guaiacol peroxidase. Furthermore, as a non-Cd hyperaccumulator plant, ramie hyperaccumulated Cd and suffered more severe toxic effects of Cd by the treatment of 1mM Ca/Cd. The aggravated Cd toxicity could be compensated by the addition of exogenous Spd via the promotion of plant growth and the reduction of the oxidative stress. Overall, the combination effects of 1mM Ca and Spd appeared to be more superior compared to other treatments in the plants under Cd stress with a higher Cd accumulation ability and the evaluated Cd stress tolerance.

Overexpression of ThVHAc1 and its potential upstream regulator, ThWRKY7, improved plant tolerance of Cadmium stress.

As one of the most toxic heavy metals in the environment, cadmium (Cd) poses a severe threat to plant growth. We previously reported that overexpression of the Tamarix hispida V-ATPase c subunit (ThVHAc1) improved the Cd tolerance of Saccharomyces cerevisiae. In the current study, we further explored the Cd tolerance conferred by ThVHAc1 in Arabidopsis and T. hispida. ThVHAc1 transgenic Arabidopsis had higher seed germination, biomass, and chlorophyll content under CdCl2 treatment. In Cd-stressed plants, overexpression of ThVHAc1 significantly improved V-ATPase activity and affected the expression of other V-ATPase subunit-encoding genes. Intriguingly, the lower level of ROS accumulation in ThVHAc1-overexpressing lines under CdCl2 treatment demonstrated that ThVHAc1 may modulate Cd stress tolerance by regulating ROS homeostasis. Transient expression of ThVHAc1 in T. hispida further confirmed these findings. Furthermore, promoter analysis and yeast one-hybrid assay revealed that the transcription factor ThWRKY7 can specifically bind to the WRKY cis-element in the ThVHAc1 promoter. ThWRKY7 exhibited similar expression patterns as ThVHAc1 under CdCl2 treatment and improved Cd tolerance, suggesting that ThWRKY7 may be an upstream regulatory gene of ThVHAc1. Therefore, our results show that the combination of ThVHAc1 and its upstream regulator could be used to improve Cd stress tolerance in woody plants.

Modulatory role of mineral nutrients on cadmium accumulation and stress tolerance in Oryza sativa L. seedlings.

Cadmium (Cd)-contaminated rice is a serious health concern. In the present study, Cd accumulation and stress responses in Oryza sativa L. cv MTU 7029 seedlings were characterized under varying concentrations of plant nutrients in Hoagland media. It has been found that nutrient supplement modulates Cd accumulation and related stress tolerance while efficacy of each nutrient varies. Supplementation of Fe, Mn, N, Ca, and S were found to reduce Cd accumulation in leaf whereas Mn and Fe supply effect was also observed in roots. Analysis of maximum quantum efficiency of photosynthesis indicated that Fe and S supplements confer highest Cd stress tolerance. The present study highlighted the potential of plant nutrients for minimizing Cd accumulation and its toxicity in rice seedlings.

Cadmium toxicity in Maize (Zea mays L.): consequences on antioxidative systems, reactive oxygen species and cadmium accumulation.

Increased cadmium (Cd) accumulation in soils has led to tremendous environmental problems, with pronounced effects on agricultural productivity. Present study investigated the effects of Cd stress imposed at various concentrations (0, 75, 150, 225, 300, 375 μM) on antioxidant activities, reactive oxygen species (ROS), Cd accumulation, and productivity of two maize (Zea mays L.) cultivars viz., Run Nong 35 and Wan Dan 13. Considerable variations in Cd accumulation and in behavior of antioxidants and ROS were observed under Cd stress in both maize cultivars, and such variations governed by Cd were concentration dependent. Exposure of plant to Cd stress considerably increased Cd concentration in all plant parts particularly in roots. Wan Dan 13 accumulated relatively higher Cd in root, stem, and leaves than Run Nong 35; however, in seeds, Run Nong 35 recorded higher Cd accumulation. All the Cd toxicity levels starting from 75 μM enhanced H2O2 and MDA concentrations and triggered electrolyte leakage in leaves of both cultivars, and such an increment was more in Run Nong 35. The ROS were scavenged by the enhanced activities of superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, and glutathione peroxidase in response to Cd stress, and these antioxidant activities were higher in Wan Dan 13 compared with Run Nong 35 at all Cd toxicity levels. The grain yield of maize was considerably reduced particularly for Run Nong 35 under different Cd toxicity levels as compared with control. The Wan Dan 13 was better able to alleviate Cd-induced oxidative damage which was attributed to more Cd accumulation in roots and higher antioxidant activities in this cultivar, suggesting that manipulation of these antioxidants and enhancing Cd accumulation in roots may lead to improvement in Cd stress tolerance.

Operative photo assimilation associated proteome modulations are critical for iron-dependent cadmium tolerance in Oryza sativa L.

Iron-dependent Cd tolerance in Oryza sativa L. cv 7029 had been explored. Photo assimilatory process such as photosynthesis and nitrogen fixation found to be functional in the presence of excess Fe during Cd stress. Cd-inducible Fe deficiency demonstrated with upregulation of iron uptake gene families such as OsIRT and OsYSL was attributed as foremost reason for retardation of photo assimilation in the course of Cd treatment. Upholding of photo assimilation during Fe supplement was associated with proteome modulations. Monitoring of proteome responses in leaf and root revealed proteins imperative for alleviation of Cd stress. Specifically, proteins that take part in photosynthesis, glucose metabolism, nitrogen fixation, and abiotic stress tolerance played key role in Fe-dependent Cd detoxification. It is concluded that Fe supply help to operate photo assimilation which enable favorable proteome responses of Cd stress tolerance.

LcBiP, a endoplasmic reticulum chaperone binding protein gene from Lycium chinense, confers cadmium tolerance in transgenic tobacco

Cadmium (Cd) accumulation is very toxic to plants. The presence of Cd may lead to excessive production of reactive oxygen species (ROS), and then cause inhibition of plant growth. The endoplasmic reticulum chaperone binding protein (BiP) is an important functional protein, which has been shown to function as a sensor of alterations in the ER environment. BiP overexpression in plants was shown to increase drought tolerance through inhibition of ROS accumulation. Due to the above relationships, it is likely that there may be a link between Cd stress tolerance, ROS accumulation and the BiP transcript expression in plants. In this study, a BiP gene, LcBiP, from L. chinense was isolated and characterized. Overexpression of LcBiP in tobacco conferred Cd tolerance. Under Cd stress conditions, the transgenic tobacco lines exhibited better chlorophyll retention, less accumulation of ROS, longer root length, more glutathione (GSH) content, and less antioxidant enzyme activity than the wild type. These data demonstrated that LcBiP act as a positive regulator in Cd stress tolerance. It is hypothesized that the improved Cd tolerance of the transgenic tobacco plants may be due to the enhanced ROS scavenging capacity. The enhancement of GSH content might contribute to this ROS scavenging capacity in the transgenic plants. However, the underlying mechanism for BiP-mediated increase in Cd stress tolerance need to be further clarified.