Goat horns: Platforms for viroid transmission to fruit trees?

Mechanical inoculations with contaminating tools and propagation of infected budwood were considered the main causes for the omnipresence of multiple viroid species among citrus and other Middle Eastern and Mediterranean fruit trees and grapevines. However, neither means could explain viroid infections of wild trees — scattered on terrains inaccessible to humans — nor the finding of similar viroids among graft-incompatible plants. Northern hybridization of RNA extracts made of scrapings from the surfaces of goat (Capra hircus) horns that were rubbed against etrog (Citrus medica) stems infected with a citrus viroids complex, revealed accumulation of considerable amounts ofCitrus exocortis viroids (CEVd) andHop stunt viroids (HSVd). Experimental transmission of both CEVd and HSVd was obtained by rubbing healthy citrus plants with goat horns that had been rubbed 24 h earlier on infected etrog stems. These results implicate goats as possible vectors of viroids. Transmissionvia goats could have facilitated the long-range spread of viroids among cultivated and wild plants andvice versa and also among graft-incompatible plants.     

Frequent mutation of BAP1 in metastasizing uveal melanomas

Metastasis is a defining feature of malignant tumors and is the most common cause of cancer-related death, yet the genetics of metastasis are poorly understood. We used exome capture coupled with massively parallel sequencing to search for metastasis-related mutations in highly metastatic uveal melanomas of the eye. Inactivating somatic mutations were identified in the gene encoding BRCA1-associated protein 1 (BAP1) on chromosome 3p21.1 in 26 of 31 (84%) metastasizing tumors, including 15 mutations causing premature protein termination and 5 affecting its ubiquitin carboxyl-terminal hydrolase domain. One tumor harbored a frameshift mutation that was germline in origin, thus representing a susceptibility allele. These findings implicate loss of BAP1 in uveal melanoma metastasis and suggest that the BAP1 pathway may be a valuable therapeutic target.     

Heavy Metal Biosorption by Plant Biomass of the Macrophyte Ludwigia Stolonifera

Ludwigia stolonifera biomass of roots, floating roots and leaves were tested for their performance as heavy metal biofilters. Cadmium (Cd) and nickel (Ni) (50 ppm) solutions were filtered through 0.5–1.5 g packed columns with each biomaterial, to determine their metal removal efficiency. Root column was more efficient in removing Ni (as low as 6 ppb in the effluent) than of Cd (as low as to 22 ppb in the effluent). This tendency was also observed upon treatment of a mixed solution of both metals. Floating roots column reduced Cd content to the same level as the root column, but its metal binding capacity was higher; 93 mg Cd g^-1 DW in floating roots in comparison to 43 mg Cd g^-1DW in the roots biofilter. Leaf biomass column demonstrated the best metal binding capacity; 128 mg Cd g^-1 DW, and Cd concentration in the effluent was 17 ppb. Pectin content was 5, 8 and 10% W/W in roots, leaves and floating roots biofilters, respectively. It seems that ion exchange is the major mechanism by which the metal is biosorbed. Evidence for the exchange of the bound heavy metal ions against the discharge of light metal ions such as calcium (Ca), magnesium (Mg), potassium (K) and sodium (Na) was provided.     

Effect of Cadmium and Iron on Rice (Oryza Sativa L.) Plant in Chelator-Buffered Nutrient Solution

ABSTRACT

To better understand the mechanisms responsible for differences in uptake and distribution of cadmium (Cd), nutrient-solution experiments were conducted with different varieties of rice (Oryza sativa), ‘Khitish’ and ‘CNRH3’. The plants were grown in a complete nutrient solution with different levels of pCd (-log free Cd⁺² activity) and pFe [-log free iron (Fe⁺²) activity]. The required concentrations of chelating agent and metals were determined using a computerized chemical equilibrium model such as Geochem-PC. Experimental treatments included a combination of four pCd activity levels (0, 7.9, 8.2, and 8.5) applied as Cd (NO₃)₂ 4H₂O, and two pFe activity levels (17.0 and 17.8) applied as FeCl₃. The application of both Cd and Fe in solution culture significantly affected plant growth, yield, and Cd accumulation in plant tissue. In general, yield of rice was decreased by an increase in amount of solution Cd; however, yield response varied among the cultivars. At the 7.9 pCd level, yields of rice cultivars ‘Khitish’ and ‘CNRH3’ were reduced to 69% and 65%, respectively, compared with control plants. Root Cd concentrations ranged from 2.6 mg kg^?1 (control plants) to 505.7 mg kg^?1 and were directly related to solution Cd concentrations. In rice plants, Cd toxicity symptoms resembled Fe chlorosis. Differential tolerance of varieties to phytotoxicity was not readily visible, but a significant interaction of substrate Cd and variety was obtained from dry-matter yields. Significant interactions indicated that response of tissue Cd concentration, plant Cd uptake, and translocation of Cd to the aerial parts were dependent on variety as well as substrate Cd. Uptake of Cd by roots was significantly higher than by shoots. Higher Cd uptake by rice plants decreased the uptake of other beneficial metals.

The effect of Cd and Fe on the rate of phytometallophore release was also studied in the nutrient solution. Among the rice genotypes, ‘Khitish’ was the most sensitive to Cd toxicity. In both genotypes, with the onset of visual Cd-toxicity symptoms, the release of phytometallophore (PM) was enhanced. Among the rice varieties, ‘Khitish’ had the highest rate of PM release. Treatments with the metal ions studied produced a decrease in chlorophyll and enzyme activity. A decrease in concentrations of chlorophyll pigments in the third leaf was observed due to the highest activity level of Cd (pCd 7.9). Activities of enzymes such as peroxidase (POD) and superoxide dismutase (SOD) are altered by toxic amounts of Cd. Changes in enzyme activities occurred at the lowest activity of Cd (pCd 8.5) in solution. Peroxidase activity increased in the third leaf. Results showed that in contrast with growth parameters, the measurements of enzyme activities may be included as early biomarkers in a plant bioassay to assess the phytotoxicity of Cd-contaminated solution on rice plants. Evidence that Cd uptake and translocation are genetically controlled warrants the selection of varieties that assimilate the least Cd and that translocate the least metal to the plant part to be used for human and animal consumption.     

Aluminium tolerance mechanisms in Phaseolus vulgaris L.: Citrate synthase activity and TTC reduction are well correlated with citrate secretion

We characterised the physiological mechanisms of tolerance in two bean varieties (Phaseolus vulgaris L. viz. French Bean cv. Amy and Rosecoco (GLP2)) differing in Al tolerance of the varietal level. Root elongation at varying levels of Al over time clearly showed the Al tolerance superiority of Rosecoco over French bean. Aluminium uptake was much higher in French bean, in both root apex and 2 mm region of the root apex. The root cation exchange capacity of the Al-sensitive French bean was markedly higher than that of Rosecoco. Citric acid was the only organic acid whose secretion was stimulated by Al and was higher in Rosecoco than in French bean. The citrate synthase and NADP⁺-isocitrate dehydrogenase activities were apparently higher in Rosecoco than in French bean b1,lt those of phosphoenolpyruvate carboxylase were not significantly different between the two varieties under Al stress. Triphenyl-tetrazolium chloride (TTC) reduction was greater in Rosecoco and was also well correlated with the citrate secretion. These results suggest the role of TTC reduction and citrate secretion as underlying factors in the Al tolerance mechanism of Rosecoco.     

The influence of phytoestrogens and oestradiol-17β on growth and sex determination in the European eel (Anguilla anguilla)

Under aquaculture conditions, European eels (Anguilla anguilla) produce a high percentage of males (80–95%) that normally stop growing at 100–200 g. Females continue to grow to 500–750 g and obtain higher market value. Therefore, increasing the percentage of females in a population would be beneficial to the culture of eels. The present study was carried out in order to examine the effect of oestradiol and phytooestrogens on sex differentiation and growth rate of eels. Juvenile European eels with undifferentiated gonads were fed pellets containing oestradiol‐17β (E2) or phytooestrogens for 100–150 days. Feeding E2 resulted in 50–61% increase in body weight compared with the control. Oestradiol‐17β and phytooestrogens both elevated significantly the percentage of females in the population. Feeding E2 at 20 mg kg^?1 feed resulted in 70% females, while lower concentration of E2 (2 mg kg^?1) resulted in only 30% after 100 days (Experiment 1). The same dose given for 150 days (Experiment 2) resulted in 88% females, indicating that both, the concentration and duration of E2 treatments had a significant effect on sex differentiation. Fish fed genistein at 2 mg kg^?1 for 100 days, resulted in 55% of females, but at a higher dose of 20 mg kg^?1 there were only 15% females. These results demonstrate that phytooestrogens can be used as alternatives to gonadal steroids for sex manipulation in eels, but the optimal concentrations and duration are still to be determined.     

A productivity model for first thinning of Pinus patula using a tractor and double-drum winch in South Africa

The productivity of skidding tractors in intermediate harvesting operations has not been determined in Mpumalanga, South Africa. The objective of this study was to develop a productivity model using a farm tractor in first thinning operations in Pinus patula compartments. A work study design was used to assess the performance of a skidding agricultural tractor. From 350 samples, important data variables collected were elemental times for each work cycle, extraction distance, slope and load volume. Stepwise and subsets regression analyses were conducted prior to multiple linear regression analysis. Analysis of variance was used to compare mean productivity estimates of the different models developed. Results showed that the best model was estimated by an interaction of distance × slope (ds), distance × load volume (dv) and slope × load volume (sv) as follows: ln(?₂) = 1.33–0.00154ds + 0.00174dv + 0.161sv. The mean estimate for this model was 5.036 m³ m h^?1. The developed models predicted similar results to estimation results of the observed model, although there were statistically significant (P < 0.001) differences among mean estimates (3.6–5.5 m³ m h^?1). All of the three models yielded R²_adj. = 38%; SE = 0.458% at P < 0.001. It can be speculated that the remaining variation not explained by the models may be associated with long extraction distances, delays and the effect of slope as a main variable in the model. While the developed models mirrored reasonably well with the observed estimates of skidding productivity, these models should not be stretched to conditions dissimilar to those of their generation. Future research focus should be made on (1) effects of weather conditions and vehicular characteristics on skidding productivity and (2) the effect of winching lines on skidding productivity.     

Removal of Silver and Lead Ions from Water Wastes Using Azolla filiculoides, an Aquatic Plant, Which Adsorbs and Reduces the Ions into the Corresponding Metallic Nanoparticles Under Microwave Radiation in 5?min

Pollution of water bodies with heavy metal ions is a major worldwide environmental problem. The objective of this study was to elucidate the mechanism in which metallic ions are adsorbed and reduced to metallic nanoparticles onto plant materials using microwave radiation. In this research, we have fabricated metallic silver and lead nanoparticles from their corresponding ions using the aquatic plants Azolla filiculoides and Pistia stratiotes (since identical results are obtained for both plants, the emphasis will be on the Azolla) under microwave radiation. Our data show that metallic silver and metallic lead nanoparticles were completely removed from the polluted solution and were embedded in the A. filiculoides surface after 5 min of microwave reaction. It was also found that, for both metals, reduction of the metallic ions was accomplished by the plant matrix without the need of an external reducing agent. Most of the particles had a spherical shape within the 10?C50 nm size range. Mass balance data clearly indicate that most of the silver particles were found on the surface of the plant and not in the clean water. Pectin and ??-glucuronic acid did not reduce the silver or lead ions under microwave radiation. We therefore hypothesize that perhaps the proteins or sugar alcohols in the plant matrix were serving as the reducing agents. We believe that this technique in which adsorption and reduction are combined using microwave radiation can be applied for removing and recycling metallic ions from contaminated water and industrial wastewater.     

Overexpression of parathion hydrolase in Escherichia coli stimulates the synthesis of outer membrane porin OmpF

Parathion hydrolase (PH), also known as organophosphorus acid anhydrase, hydrolyses the triester linkage found in organophosphates including organophosphate pesticides and the nerve gas sarin. The enzyme is reported to be membrane-associated and the immature protein has a signal sequence of 29 amino acids. In experiments designed to examine the post-translational processing of the enzyme and to assess the distribution of the precursor and mature forms of the protein, we induced expression of the Flavobacterium balustinum PH structural gene, opd, in Escherichia coli strain BL21. Western blotting revealed that the induced PH was predominantly membrane-associated in E. coli but a protein band equivalent in size to mature PH was also found to be induced specifically in periplasmic fractions. This periplasmic protein was not PH, as it did not cross-react in Western blots, and N-terminal sequencing of the induced protein showed it to have 100% homology to the outer membrane protein OmpF.