Interactive effects of excessive potassium and Mg deficiency on safflower

In the present work, separate and combined effects of excessive potassium and magnesium deficiency on safflower (Carthamus tinctorius) were studied. Four treatments were considered: C (control treatment: complete medium containing 1.5 mM Mg), +KCl (excessive potassium treatment: complete medium added with 60 mM KCl), ?Mg (Mg-deficient treatment: containing 0.1 mM Mg), and DS (double stress treatment: Mg-deficient medium (0.1 mM Mg) added with 60 mM KCl. Excessive potassium effect on plant growth was more pronounced than that of Mg deficiency. The two stresses impaired differently plant organs; KCl application affected more roots than shoots, whereas Mg deficiency reduced only leaf biomass. Gas exchange and pigment concentrations and patterns were severely impaired by KCl and mainly by interactive effects of the two stresses. This led to obvious lipid peroxidation and electrolyte leakage. Mg deficiency did not induce lipid peroxidation and electrolyte leakage, but as applied with excessive potassium, it doubled the effect of the latter. Mineral analyses showed that major cation nutrition was disturbed by KCl and combined stresses and at a lower level by magnesium deficiency. Plants did not show an enhanced selectivity of Mg and Ca over K but they improved their use efficiencies.     

Antioxidant enzymes activities and bilirubin level in adult rat treated with lead

Lead toxicity is closely related to its accumulation in several tissues and its interference with bioelements, whose role is critical for several biological processes. Recently, oxidative stress has been proposed as a possible mechanism involved in lead toxicity. This study was carried out to investigate the effect of dose-dependent lead exposure on haematological and oxidative stress parameters. Adult male 'Wistar' rats (150-200 g) were divided into three groups: group [Pb 5] and group [Pb 15] received respectively 5 mg Pb(2+) (n=16) and 15 mg Pb(2+)/kg b.w. (n=16) as lead acetate solution i.p. for a period of seven days. Group [T] (n= 16) served as control and received 15 mg Na(+)/kg b.w. as sodium acetate solution i.p. for the same period. All animals were sacrificed 24 h after the last injection. Blood superoxide dismutase (SOD) and blood glutathione peroxidase (GPx) activities and plasma bilirubin level were measured. Liver was quickly excised for the estimation of alteration in lipid peroxidation indices (MDA). Lead exposure induces, in both treated groups, a marked decline in haematocrit and haemoglobin levels (p<0.01) when compared to control. The results show also a significant decrease (p<0.01) in SOD activity, but only in group [Pb 15]. SOD activity did not decrease in group [Pb 5] in comparison with control (p>0.05). However, lead exposure caused a light increase in GPx activity in group [Pb 15], which remains non-significant (p>0.05) compared to control. Group [Pb 5] did not record significant changes in the activity of GPx. Lead exposure for a period of seven days resulted in a significant (p<0.05) increase in bilirubin level in group [Pb 15] compared to control. The bilirubin level from rats of group [Pb 5] did not reach a statistical significance. Changes in liver MDA content in lead-exposed rats from [Pb 5] and [Pb 15] groups did not reach a statistical (p<0.05) significance. It is concluded that lead induces oxidative stress in a dose-dependent manner. No dose-dependent response was observed in blood GPx activity and liver MDA content. These results could be due to the short duration of the treatment.     

Host plant defenses of black (Solanum nigrum L.) and red nightshade (Solanum villosum Mill.) against specialist Solanaceae herbivore Leptinotarsa decemlineata (Say)

Black nightshade (Solanum nigrum, S. nigrum L.) and red nightshade ( Solanum villosum, S. villosum Mill.) are medicinal plants from the Solanaceae family that synthesize glycoalkaloids and other secondary metabolites. To recognize the potential insecticide activity of these compounds, leaf extracts (containing glycoalkaloid and methanol fractions) were tested for enzyme inhibition, antifeedant activity and toxicity. For in‐vitro glutathione S‐transferase (GST) inhibition activity, we used insecticide‐resistant Colorado potato beetle, Leptinotarsa decemlineata ( L. decemlineata; Say) midgut and fat‐body homogenate. In‐vivo toxicity and the antifeedant activity were performed using larval bioassays. The methanol extracts had greater GST inhibitory activity compared to the glycoalkaloids, as well as greater 2nd instar larvae mortality and antifeedant activity. Furthermore, the green leaf volatile compound, cis‐hex‐3‐enyl acetate, at the concentration of 5 ppm, caused 50% mortality of 2nd instar larvae. Our findings suggest the potential usefulness of S. nigrum and S. villosum extracts to control L. decemlineata.     

Comparison of Leishmania killicki (syn. L. tropica) and Leishmania tropica Population Structure in Maghreb by Microsatellite Typing

Leishmania (L.) killicki (syn. L. tropica), which causes cutaneous leishmaniasis in Maghreb, was recently described in this region and identified as a subpopulation of L. tropica. The present genetic analysis was conducted to explore the spatio-temporal distribution of L. killicki (syn. L. tropica) and its transmission dynamics. To better understand the evolution of this parasite, its population structure was then compared with that of L. tropica populations from Morocco. In total 198 samples including 85 L. killicki (syn. L. tropica) (from Tunisia, Algeria and Libya) and 113 L. tropica specimens (all from Morocco) were tested. Theses samples were composed of 168 Leishmania strains isolated from human skin lesions, 27 DNA samples from human skin lesion biopsies, two DNA samples from Ctenodactylus gundi bone marrow and one DNA sample from a Phlebotomus sergenti female. The sample was analyzed by using MultiLocus Enzyme Electrophoresis (MLEE) and MultiLocus Microsatellite Typing (MLMT) approaches. Analysis of the MLMT data support the hypothesis that L. killicki (syn. L. tropica) belongs to the L. tropica complex, despite its strong genetic differentiation, and that it emerged from this taxon by a founder effect. Moreover, it revealed a strong structuring in L. killicki (syn. L. tropica) between Tunisia and Algeria and within the different Tunisian regions, suggesting low dispersion of L. killicki (syn. L. tropica) in space and time. Comparison of the L. tropica (exclusively from Morocco) and L. killicki (syn. L. tropica) population structures revealed distinct genetic organizations, reflecting different epidemiological cycles.     

Nutrient uptake and management under saline conditions in the xerohalophyte: Tecticornia indica (Willd.) subsp. indica

In the present investigation, we studied uptake and management of the major cations in the xerohalophyte, Tecticornia indica (Willd.) subsp. indica as subjected to salinity. Plants were grown under greenhouse conditions at various salinity levels (0, 100, 200 and 400 mM NaCl) over 110 days. At harvest, they were separated into shoots and roots then analyzed for water contents, dry weights (DW), and Na+, K+, Ca2+, and Mg2+ contents. Plants showed a growth optimum at 200 mM NaCl and much better tissue hydration under saline than non-saline conditions. At this salt concentration (200 mM NaCl), shoot Na+ content reached its highest value (7.9 mmol · g-?1 DW). In spite of such stressful conditions, salt-treated plants maintained adequate K+, Ca2+, and Mg2+ status even under severe saline conditions. This was mainly due to their aptitude to selectively acquire these essential cations and efficiently use them for biomass production.     

Steroid 21-hydroxylase gene mutational spectrum in 50 Tunisian patients: Characterization of three novel polymorphisms

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disease of steroid biosynthesis in humans. More than 90% of all CAH cases are caused by mutations of the 21-hydroxylase gene (CYP21A2), and approximately 75% of the defective CYP21A2 genes are generated through an intergenic recombination with the neighboring CYP21A1P pseudogene. In this study, the CYP21A2 gene was genotyped in 50 patients in Tunisia with the clinical diagnosis of 21-hydroxylase deficiency. CYP21A2 mutations were identified in 87% of the alleles. The most common point mutation in our population was the pseudogene specific variant p.Q318X (26%). Three novel single nucleotide polymorphism (SNP) loci were identified in the CYP21A2 gene which seems to be specific for the Tunisian population. The overall concordance between genotype and phenotype was 98%. With this study the molecular basis of CAH has been characterized, providing useful results for clinicians in terms of prediction of disease severity, genetic and prenatal counseling.     

Salt-imposed restrictions on the uptake of macroelements by roots of Arabidopsis thaliana

The aim of this investigation was to identify the growth limiting factors in Arabidopsis thaliana subjected to a mild salt stress. Two natural accessions (Col and N1438) were compared. In spite of their morphological and developmental similarity, they have been previously shown to differ in the response of their superoxide dismutase genes to salt stress (Physiol Plant 132:293–305, 2008). Thirty-day-old seedlings were grown for 15 days using a split-root configuration in which the root system was divided into two equal parts: the first was immersed in a complete nutrient solution with 50 mM NaCl added, while the second part was immersed in either complete or incomplete K-, Ca-, or N-free medium. Using this approach, we demonstrated that K⁺ and Ca²⁺ uptake was impaired in the roots subjected to NaCl. There was no indication of the salt-induced inhibition of N uptake. If K⁺ or Ca²⁺ were available from salt-free medium, plants were able to grow at normal rate and accumulate large amounts of Na⁺ in the shoots. These results indicate that the sensitivity of Arabidopsis growth to mild salinity was probably due to an inhibition of K⁺ or Ca²⁺ root transport by salt rather than due to salt accumulation in shoots. Furthermore, the salt sensitivity of ion transport in roots seemed to depend on the genotype, since K⁺ was limiting for Col growth, in contrast to N1438, the growth of which was limited by Ca²⁺.     

Sodium transport in basil

In order to diversify the production of plants with pharmacological interest, it is important to understand the mechanisms involved in their tolerance to environmental constraints, such as salinity. Basil (Ocimum basilicum), known for its therapeutic uses, has been claimed to be salt tolerant, but physiological aspects of this behavior remain unknown. Since salt tolerance is known to be associated with several characteristics concerning Na⁺ transport to leaves, we studied this function in hydroponically grown basil. We analyzed the response of 30-day-old seedlings to 25–50 mM NaCl applied for 15 days. Growth was poorly affected, indicating that these concentrations corresponded to the tolerated salinity range. Leaves accumulated Na⁺ at relatively high concentration, without dehydrating. Potassium concentration in leaf tissues was maintained close to control level, indicating that K⁺ was 15- to 25-fold preferred over Na⁺ for ion transport and deposition. Collection of xylem sap on detopped plants revealed that this preference was only 10-fold for ion introduction into root xylem sap. Short-term (24 h) changes in Na⁺ distribution between organs after stem (steam) girdling suggested that Na⁺ downward recirculation by phloem occurred. Although modest, this transport might have augmented K⁺ selectivity of ion deposition in leaves.     

Responses of Arabidopsis thaliana to bicarbonate-induced iron deficiency

Morpho-physiological and biochemical responses of Arabidopsis thaliana (accession N1438) to bicarbonate-induced iron deficiency were investigated. Plants were grown in cabinet under controlled conditions, in a nutrient solution containing 5 μM Fe, added or not with 10 mM NaHCO₃. After 30 days, bicarbonate-treated plants displayed significantly lower biomass, leaf number and leaf surface area as compared to control plants, and slight yellowing of their younger leaves was observed. Potassium (K⁺) content was not modified by bicarbonate treatment in roots, whereas it was significantly diminished in shoots. Their content in ferrous iron (Fe²⁺) and in leaf total chlorophylls was noticeably lower than in control plants. Root Fe(III)-chelate reductase and phosphoenolpyruvate carboxylase (PEPC) activities were significantly enhanced, but leaf ribulose 1.5-bisphosphate carboxylase (Rubisco) activity was decreased.