Distribution Of Cd In Plants Research Articles

CDR1, a DUF946 domain containing protein, positively regulates cadmium tolerance in Arabidopsis thaliana by maintaining the stability of OPT3 protein

Industrial and agricultural production processes lead to the accumulation of cadmium (Cd) in soil, resulting in crops absorb Cd from contaminated soil and then transfer it to human body through the food chain, posing a serious threat to human health. Thus, it is necessary to explore novel genes and mechanisms involved in regulating Cd tolerance and detoxification in plants. Here, we found that CDR1, a DUF946 domain containing protein, localizes to the plasma membrane and positively regulates Cd stress tolerance. The cdr1 mutants exhibited Cd sensitivity, accumulated excessive Cd in the seeds and roots, but decreased in leaves. However, CDR1-OE transgenic plants not only showed Cd tolerance but also significantly reduced Cd in seeds and roots. Additionally, both in vitro and in vivo assays demonstrated an interaction between CDR1 and OPT3. Cell free protein degradation and OPT3 protein level determination assays indicated that CDR1 could maintain the stability of OPT3 protein. Moreover, genetic phenotype analysis and Cd content determination showed that CDR1 regulates Cd stress tolerance and affect the distribution of Cd in plants by maintaining the stability of OPT3 protein. Our discoveries provide a key candidate gene for directional breeding to reduce Cd accumulation in edible seeds of crops.

Molecular mechanisms and physiological responses of rice leaves co-exposed to submicron-plastics and cadmium: Implication for food quality and security

The effects of co-exposure to aged submicron particles (aSMPs) and Cd as model contaminants on rice leaves via the foliar route were investigated. Thirty-day-old rice seedlings grown in soil were exposed to Cd (nitrate) through foliar spraying at concentrations of 1, 10, 50, 100, and 500 μM, with or without aSMP at a rate of 30 μg d−1. It was observed that Cd translocated from leaves to roots via stems even without co-exposure to SMP. Co-exposure can reduce cadmium levels in leaves. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis confirmed a significant reduction (29.3 − 77.9%) in Cadmium accumulation in the leaves of rice plants during co-exposure. Exposure to Cd resulted in physiological, transcriptomic, and metabolomic changes in rice leaves, disrupting 28 metabolism pathways, and impacting crop yield and quality. Exposure to both Cd and aSMPs can interfere with the Cd distribution in plants. Rice leaves exposed solely to Cd exhibit higher toxicity and Cd accumulation, compared to those co-exposed to Cd and aSMPs. The accumulation of Cd in plant leaves is enhanced with aSMPs, which may lead to more pronounced gene expression regulation and changes in metabolic pathways, compared to Cd exposure. Our study found that the independent Cd exposure group had higher Cd accumulation and toxicity in rice leaves compared to the combined exposure of Cd and aSMPs. We hypothesize that aged negatively charged SMPs can capture Cd and reduce its exposure in the free state while jointly inhibiting Cd-induced oxidative and chloroplast damage, thereby reducing the potential risk of Cd exposure in rice plants.

Overexpression of ApHIPP26 from the Hyperaccumulator Arabis paniculata Confers Enhanced Cadmium Tolerance and Accumulation to Arabidopsis thaliana.

Cadmium (Cd) is a toxic heavy metal that seriously affects metabolism after accumulation in plants, and it also causes adverse effects on humans through the food chain. The HIPP gene family has been shown to be highly tolerant to Cd stress due to its special domain and molecular structure. This study described the Cd-induced gene ApHIPP26 from the hyperaccumulator Arabis paniculata. Its subcellular localization showed that ApHIPP26 was located in the nucleus. Transgenic Arabidopsis overexpressing ApHIPP26 exhibited a significant increase in main root length and fresh weight under Cd stress. Compared with wild-type lines, Cd accumulated much more in transgenic Arabidopsis both aboveground and underground. Under Cd stress, the expression of genes related to the absorption and transport of heavy metals underwent different changes in parallel, which were involved in the accumulation and distribution of Cd in plants, such as AtNRAMP6 and AtNRAMP3. Under Cd stress, the activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase) in the transgenic lines were higher than those in the wild type. The physiological and biochemical indices showed that the proline and chlorophyll contents in the transgenic lines increased significantly after Cd treatment, while the malondialdehyde (MDA) content decreased. In addition, the gene expression profile analysis showed that ApHIPP26 improved the tolerance of Arabidopsis to Cd by regulating the changes of related genes in plant hormone signal transduction pathway. In conclusion, ApHIPP26 plays an important role in cadmium tolerance by alleviating oxidative stress and regulating plant hormones, which provides a basis for understanding the molecular mechanism of cadmium tolerance in plants and provides new insights for phytoremediation in Cd-contaminated areas.

Distribution of Cadmium in Sweet Corn Grown on a Peat Soil and Its Implication on Food Safety

Cadmium (Cd) is a heavy metal that can contaminate agricultural soils, in which one of the sources of Cd in agricultural soils is the use of phosphate fertilizers. Some plant species are known to have the ability to accumulate large amounts of Cd in their organs despite the Cd content in soil is relatively small. Cadmium distribution in various organs of plants also shows a diverse variation. Maize is able to accumulate Cd in its organs, either in roots, leaves or grains. This study aims to determine the distribution of Cd in sweet corn plants grown on a peat soil. Samples of maize plants were taken from nine maize fields in the village of Rasau Jaya 1, Rasau Jaya subdistrict, Kubu Raya district, West Kalimantan. The cultivars of sweet corn planted were Zea mays saccharata cultivar Bonanza and Zea mays saccharata cultivar Secada. Samples for roots, leaves, stems and panicles were taken at the stage of early grain filling. Grain samples were taken at the phase of fresh pod consumption. The Cd contents in the plant organ tissues were determined using dry ashing method. The results showed that the distribution of Cd in plant organs of sweet corn cultivars Secada and Bonanza follows the pattern of Cd in leaves > roots > grains > panicles > stems. The leaves contain the highest concentration of Cd, while the stems contain the lowest amount of Cd. The Cd concentration in leaves is about 3.5 times higher than that in grains, and 1.5 times higher than that in roots. The average Cd content in grains of sweet corn is 0.037 mg kg-1, which is still below the safe limit of Cd content in grains allowed by the Standar Nasional Indonesia, i.e. 0.2 mg kg-1.

Specific mechanisms of tolerance to copper and cadmium are compromised by a limited concentration of glutathione in alfalfa plants

The induction of oxidative stress is a characteristic symptom of metal phytotoxicity and is counteracted by antioxidants such as glutathione (GSH) or homoglutathione (hGSH). The depletion of GSH│hGSH in fifteen-day-old alfalfa (Medicago sativa) plants pre-incubated with 1mM buthionine sulfoximine (BSO) affected antioxidant responses in a metal-specific manner under exposure to copper (Cu; 0, 6, 30 and 100μM) or cadmium (Cd; 0, 6 and 30μM) for 7 days. The phytotoxic symptoms observed with excess Cu were accompanied by an inhibition of root glutathione reductase (GR) activity, a response that was augmented in Cd-treated plants but reverted when combined with BSO. The synthesis of phytochelatins (PCs) was induced by Cd, whereas the biothiol concentration decreased in Cu-treated plants, which did not accumulate PCs. The depletion of GSH│hGSH by BSO also produced a strong induction of oxidative stress under excess Cu stress, primarily due to impaired GSH│hGSH-dependent redox homeostasis. In addition, the synthesis of PCs was required for Cd detoxification, apparently also determining the distribution of Cd in plants, as less metal was translocated to the shoots in BSO-incubated plants. Therefore, specific GSH│hGSH-associated mechanisms of tolerance were triggered by stress due to each metal.

Cadmium determinant 1 is a putative heavy‐metal transporter in Arabidopsis thaliana (617.4)

Cadmium (Cd) is a non‐essential toxic heavy metal for most organisms. Accumulation of Cd is toxic to plants, and it also causes serious health concerns in humans as plants are the major staples in human diet. In A. thaliana, cadmium is mainly accumulated in the roots suggesting that root‐to‐shoot Cd translocation is restricted at the xylem loading. Up to date, two members of HEAVY METAL P1B‐ATPase (HMA) family of transporters, namely HMA2 and HMA4, and some YSL transporters have been shown to be responsible for Cd loading into the xylem. Here we present data suggesting CADMIUM DETERMINANT 1 (CDM1) as a previously uncharacterized putative heavy‐metal transporter in plants. Expression of CDM1 was induced under Cd treatment in wild‐type seedling roots. Elemental analysis of two alleles of cdm1 mutant by ICP‐MS showed that the mutants accumulated less Cd and Zn both in shoots and roots after Cd treatment. In addition, root growth of cdm1 mutants showed higher tolerance to Cd toxicity. These data suggest that CADMIUM DETERMINANT 1 (CDM1) functions in Cd distribution in plants. Interestingly, preliminary confocal microscopy analyses of seedlings overexpressing CDM1:GFP indicated that CDM1 localized to the plastids. Further characterization of CDM1:GUS and CDM1 overexpression lines are in progress.Grant Funding Source: Supported by NSF‐MCB 0950459

Does subcellular distribution in plants dictate the trophic bioavailability of cadmium to Porcellio dilatatus (crustacea, isopoda)?

The present study examined how subcellular partitioning of Cd in plants with different strategies to store and detoxify Cd may affect trophic transfer of Cd to the isopod Porcellio dilatatus. The plant species used were Lactuca sativa, a horticultural metal accumulator species; Thlaspi caerulescens, a herbaceous hyperaccumulator species; and the nonaccumulator, T. arvense. Taking into account that differences in subcellular distribution of Cd in plants might have an important role in the bioavailability of Cd to a consumer, a differential centrifugation technique was adopted to separate plant leaf tissues into four different fractions: cell debris, organelles, heat-denatured proteins, and heat-stable proteins (metallothionein-like proteins). Plants were grown in replicate hydroponic systems and were exposed for 7 d to 100 microM Cd spiked with 109Cd. After a 14-d feeding trial, net assimilation of Cd in isopods following consumption of T. caerulescens and T. arvense leaves reached 16.0 +/- 2.33 and 21.9 +/- 1.94 microg/g animal, respectively. Cadmium assimilation efficiencies were significantly lower in isopods fed T. caerulescens (10.0 +/- 0.92%) than in those fed T. arvense (15.0 +/- 1.03%). In further experiments, Cd assimilation efficiencies were determined among isopods provided with purified subcellular fractions of the three plants. On the basis of our results, Cd bound to heat-stable proteins was the least bioavailable to isopods (14.4-19.6%), while Cd bound to heat-denatured proteins was the most trophically available to isopods (34.4-52.8%). Assimilation efficiencies were comparable in isopods fed purified subcellular fractions from different plants, further indicating the importance of subcellular Cd distribution in the assimilation. These results point to the ecological relevance of the subcellular Cd distribution in plants, which directly influence the trophic transfer of Cd to the animal consumer.