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Abstract: Catalase (CAT), an important enzyme of antioxidant system, was investigated the role in preventing the plant from Cd-induced oxidative stress caused by reactive oxygen species. A CAT gene from Brassica juncea was cloned and up-regulated in response to Cd/Zn. The CAT cDNA (BjCAT3) under the control of CaMV35S promoter was introduced into tobacco via Agrobacterium-mediated transformation. Northern blot analysis verified the BjCAT3 was expressed at high level in different transgenic lines. In morphological observation, we found that seedlings from transgenic tobacco plants grew better and showed longer root length in the presence of Cd versus wild-type (WT) seedlings. Under 100μM Cd stress, WT plants became chlorotic and almost dead while transgenic tobacco plants still remained green and phenotypically normal. The CAT activity of transgenic T1 generations was approximately two-fold higher than that of WT plants. In WT, endogenous CAT activity is rapidly reduced as a result of 200μM CdCl2 exposure. Compared with WT plants, lower level of Cd-induced H2O2 accumulation and cell death were detected in roots of transgenic plants with high level of CAT activity. All our findings strongly support that overexpressing BjCAT3 in tobacco could enhance the tolerance under Cd stress. [Copyright &y& Elsevier]

A clone of PvSR6 encoding a new member of the DnaJ-like protein family was isolated from a mercuric-chloride-treated bean (Phaseolus vulgaris L.) cDNA library by differential screening using cDNAs derived from treated and untreated plants. The predicted protein contains the highly conserved J domain only, which is present in all DnaJ-like proteins and is considered to play a critical role in DnaJ protein-protein interaction. PvSR6 gen is constitutively expressed in roots but weakly expressed in stems and leaf tissue. Northern blot analysis revealed the transcripts of PvSR6 were at low levels in unstressed bean leaves, but the genes expression was strongly stimulated by heavy metals. These suggest that the PvSR6 might play an important role in resistance to the damage caused by heavy metals. [ABSTRACT FROM AUTHOR]

The pollution of soil with heavy metals (HMs) has become an environmental problem of global concern. Phytoremediation, whereby plants extract HMs from soil, can efficiently and substantially reduce HM pollution in soil in an environmentally friendly manner. Cadmium-induced protein AS8 (CIPAS8) is present in many plants and its expression is induced by HMs. In this study, PeCIPAS8 and SlCIPAS8 were transformed into 84K poplar to study their effects on tolerance to, and translocation of, cadmium (Cd) in woody plants. Localization analyses showed that two CIPAS8 proteins were localized at the plasma membrane when transiently expressed in tobacco leaf epidermal cells. Compared with wild-type 84K poplar seedlings, transgenic poplar lines overexpressing PeCIPAS8 or SlCIPAS8 showed increased Cd contents and decreased Cd tolerance. Transgenic poplar lines overexpressing PeCIPAS8 or SlCIPAS8 accumulated more Cd in the roots, stems, and leaves, but the plant height did not differ significantly, compared with wild-type 84K poplar under Cd stress during the vegetative stage. CIPAS8 increased the Cd influx rate of transgenic poplar roots compared with that of the wild type, and affected the transcription levels of other metal transporters. These findings show that CIPAS8 increases Cd flux into plant tissues and demonstrate moderate Cd sensitivity of the plant. Therefore, CIPAS8 is an influx transporter with the potential to increase the uptake of toxic HMs by woody plants growing in HM-contaminated soils. [Display omitted] • PeCIPAS8 and SlCIPAS8 are plasma membrane proteins. • CIPAS8 -OE/X poplar showed increased Cd content and Cd hypersensitivity. • Compared with wild type, CIPAS8 -OE/X accumulated more Cd in roots, stems, and leaves. • CIPAS8 may be Cd influx transporter for Cd removal in contaminated soil. [ABSTRACT FROM AUTHOR]

Abstract: Manganese (Mn) can interact with cadmium (Cd) in environments and influence the toxic effect of Cd on plants. However, few studies have investigated the relationship between the Mn/Cd ratio and plant Cd-toxicity along Cd concentrations. In this paper, we studied the effects of external Mn/Cd molar ratios (0, 10, 30, 50 and 60) on Cd toxicity in the Mn hyperaccumulator and Cd tolerant plant, Phytolacca acinosa Roxb., at three Cd levels (50, 100 and 200 μM) under hydroponic conditions. Our result showed that seedling growth (y) under Cd stress was strongly positively related to the solution Mn/Cd molar ratio (SMCR). The relationship between the two variables under solution Cd concentrations was well explained by the linear regression model y = a + b1 (SMCR) + b2 (Solution-Cd). Increasing SMCR significantly reduced the Cd concentration and increased the Mn concentration in plant tissues. However, seedling growth was consistent with the shoot Mn/Cd molar ratio rather than with the Mn or Cd concentrations in plant tissues. At low levels of SMCR (e.g. 0 and 10), elevation of Mn distribution in shoot tissues might be a mechanism in P. acinosa seedlings to defend against Cd-toxicity. In comparison with low levels of SMCR, high levels of SMCR (e.g. 50 and 60) greatly alleviated lipid peroxidation and plant water-loss, and enhanced photosynthesis. However, the alleviated lipid peroxidation in the Mn-mitigation of Cd toxicity was likely to be the secondary effect resulting from the antagonism between Mn and Cd in the plant. [Copyright &y& Elsevier]

Abstract: Synchrotron radiation X-ray fluorescence (SRXRF) and inductively coupled plasma mass spectrometry were used to estimate major, minor and trace elements in Cu-, Zn- and Mn-treated Phytolacca americana. The effects of the addition of Cu, Zn and Mn on morphological parameters, such as root length, shoot height, and fresh and dry weights of shoots and roots, were also examined. In addition, the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidases (GPX) and catalase (CAT) and the expression of Fe-SOD, Cu/Zn-SOD, metallothionein-2 and glutathione S-transferase (GST) exposed to the highest amounts of Cu, Zn or Mn were detected. Our results confirmed the following: (1) Zn supplementation leads to chlorosis, disturbed elemental homeostasis and decreased concentrations of micro- and macroelements such as Fe, Mg, Mn, Ca and K. Cu competed with Fe, Mn and Zn uptake in plants supplemented with 25μM Cu. However, no antagonistic interactions took place between Cu, Zn, Mn and Fe uptake in plants supplemented with 100μM Cu. Mn supplementation at various concentrations had no negative effects on elemental deficits. Mn was co-located with high concentrations of Fe and Zn in mature leaves and the concentrations of macro elements were unchanged. (2) P. americana supplemented with increased concentrations of Zn and Cu exhibited lower biomass production and reduced plant growth. (3) When plants were supplemented with the highest Zn and Cu concentrations, symptoms of toxicity corresponded to decreased SOD or CAT activities and increased APX and GPX activities. However, Mn tolerance corresponded to increased SOD and CAT activities and decreased POD and APX activities. Our study revealed that heavy metals partially exert toxicity by disturbing the nutrient balance and modifying enzyme activities that induce damage in plants. However, P. americana has evolved hyper accumulating mechanisms to maintain elemental balance and redox homeostasis under excess Mn. [Copyright &y& Elsevier]

Toxic heavy metals originating from human activities have caused irreversible harm to the environment. Toxic heavy metal ions absorbed by crop plants can seriously threaten human health. Therefore, decreasing heavy metal contents in crop plants is an urgent need. The plant cadmium resistance protein (PCR) is a heavy metal ion transporter. In this study, PePCR10 was cloned from Populus euphratica. Bioinformatics analyses revealed its transmembrane structure and gene sequence motifs. The transcript profile of PePCR10 was analyzed by RT-qPCR, and its transcript levels increased under toxic heavy metal (cadmium, lead, aluminum) treatments. Subcellular localization analyses in tobacco cells revealed that PePCR10 localizes at the plasma membrane. Compared with wild type (WT), PePCR10 -overexpressing lines showed significantly higher values for plant height, root length, fresh weight, and dry weight under heavy metal stress. Electrolyte leakage, nitroblue tetrazolium staining, and chlorophyll fluorescence analyses indicated that Cd/Al tolerance in PePCR10 -overexpressing lines was stronger than that in WT. The Cd/Al contents were lower in the PePCR10 -overexpressing lines than in WT under Cd/Al stress. Our results show that PePCR10 can reduce the heavy metal content in poplar and enhance its Cd/Al tolerance. Hence, PePCR10 is a candidate genetic resource for effectively reducing heavy metal accumulation in crops. [Display omitted] • PePCR10 was confirmed to be a plasma membrane-localized protein. • PePCR10 enhanced Cd/Al tolerance by promoting Cd/Al efflux in poplar. • PePCR10 can be used to reduce the risks of heavy metals to humans. [ABSTRACT FROM AUTHOR]

Abstract: Solanum nigrum L. is considered to be a potential plant for restoring Cd-contaminated soils. Si could enhance plants tolerance to heavy metal; however, the mechanism of Si-mediated alleviation of Cd toxicity in S. nigrum was not clear. Three-week-old S. nigrum seedlings were grown in Hoagland solution containing 0 or 100 μM Cd with or without 1 mM Si for 4 days. The results showed that the Cd concentration both in roots and shoots of Si-supplied plant was significantly reduced, especially in expanding and old leaves. The relative proportion of ethanol-extractable Cd, water-extractable Cd and NaCl-extractable Cd in roots was increased by adding Si, while the root-to-shoot Cd translocation was not decreased. Furthermore, in comparison with single Cd treatment, supplying Si could reduce H2O2 accumulation and cell death in roots, and the electrolyte leakage and H2O2 concentration in functional leaves. Moreover, the activity of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7) and ascorbate peroxidase (APX, EC 1.11.1.11) in functional leaves was markedly increased by Cd exposure, while the antioxidative enzyme activities in Cd plus Si treatment seedlings were significantly lower than that in Cd treatment alone, this decrease might be attributed to the reduction of Cd concentration and Cd-induced oxidative damages. These results demonstrate that Si-enhanced Cd tolerance in S. nigrum is mainly due to the decrease of Cd uptake in roots and Cd distribution in expanding and old leaves, as well as lowering oxidative stress induced by Cd in plants. [Copyright &y& Elsevier]

Summary: The stress-related gene no. 2 of Phaseolus vulgaris (PvSR2) is metal inducible and contains a single intron. Here, we report that Zn stress inhibited the splicing of the PvSR2–β-glucuronidase (GUS) fusion gene in a concentration- and time-dependent manner in tobacco seedlings. The inhibition appears to be specific for the PvSR2–GUS transgene: splicing of four endogenous tobacco genes was unaffected by Zn stress. Our results provide in vivo evidence that Zn stress-dependent intron retention is transgene specific in plants. [Copyright &y& Elsevier]