Overexpression of wheat Na+/H+ antiporter TNHX1 and H+-pyrophosphatase TVP1 improve salt- and drought-stress tolerance in Arabidopsis thaliana plants

Transgenic Arabidopsis plants overexpressing the wheat vacuolarNa⁺/H⁺ antiporter TNHX1 and H⁺-PPase TVP1 are much more resistantto high concentrations of NaCl and to water deprivation thanthe wild-type strains. These transgenic plants grow well inthe presence of 200 mM NaCl and also under a water-deprivationregime, while wild-type plants exhibit chlorosis and growthinhibition. Leaf area decreased much more in wild-type thanin transgenic plants subjected to salt or drought stress. Theleaf water potential was less negative for wild-type than fortransgenic plants. This could be due to an enhanced osmoticadjustment in the transgenic plants. Moreover, these transgenicplants accumulate more Na⁺ and K⁺ in their leaf tissue thanthe wild-type plants. The toxic effect of Na⁺ accumulation inthe cytosol is reduced by its sequestration into the vacuole.The rate of water loss under drought or salt stress was higherin wild-type than transgenic plants. Increased vacuolar soluteaccumulation and water retention could confer the phenotypeof salt and drought tolerance of the transgenic plants. Overexpressionof the isolated genes from wheat in Arabidopsis thaliana plantsis worthwhile to elucidate the contribution of these proteinsto the tolerance mechanism to salt and drought. Adopting a similarstrategy could be one way of developing transgenic staple cropswith improved tolerance to these important abiotic stresses. Key words: H⁺-pyrophosphatase, Na⁺/H⁺ antiporter, salt and drought tolerance, sodium sequestration, transgenic Arabidopsis plants     

Architecture of the pruned tree: impact of contrasted pruning procedures over 2 years on shoot demography and spatial distribution of leaf area in apple (Malus domestica)

BACKGROUND AND AIMS: Demography and spatial distribution of shoots are rarely studied on pruned trees. The present 2-year study deals with the effect of pruning strategies on shoot demography and development, and consequences on the spatial distribution of leaf area in three architecturally contrasted - from type II to IV - apple cultivars: 'Scarletspur Delicious', 'Golden Delicious' and 'Granny Smith'. METHODS: All trees were initially subjected during 5 years to Central Leader training with winter heading on all long shoots. For 2 years, half of the trees were further trained with Centrifugal training, where removal of flowering shoots - called extinction pruning - was carried out along the trunk and at the bottom of branches at flowering time. During these 2 years, shoot type (vegetative, inflorescence) and length, and the three-dimensional spatial distribution of all shoots were assessed with an electromagnetic digitizer. KEY RESULTS: Shoot demography, frequency of transitions toward an inflorescence from either an inflorescence (bourse-over-bourse) or a vegetative shoot (trend toward flowering), and the number of bourse-shoots per bourse were strongly affected by cultivar, with little influence of tree manipulation. In contrast, the proportion of vegetative long shoots developing from previous year latent buds was significantly lower in Centrifugal-trained trees for the three cultivars. Canopy volume showed large variations between cultivars, but only that of 'Granny Smith' was affected by tree manipulation in the 2 years. Spatial distribution of shoots varied significantly according to cultivar and manipulation. In 'Scarletspur Delicious' and, to a lesser extent 'Golden Delicious', the distribution of vegetative and flowering shoots in the outer and the inner parts, respectively, was not affected by tree manipulation. In contrast, in 'Granny Smith', vegetative shoots were stimulated in the periphery of Central Leader trees, whereas flowering shoots were stimulated in the periphery of Centrifugal-trained trees. CONCLUSIONS: In apple, the variability of responses to contrasted pruning strategies partly depends on the genetically determined growth and flowering habit of the cultivar.     

Toxicological Assessment of Arsenic-Induced Hematological Alterations and Chromosomal Aberrations in Tilapia Oreochromis mossambicus

Arsenic is an environmental contaminant and potential carcinogen. Toxicological assessment of As, which causes hematological alterations and chromosomal aberrations, was studied in freshwater fish Oreochromis mossambicus. Fish were exposed to 3 ppm, 28 ppm, and 56 ppm concentrations of sodium arsenite (NaAsO₂) and blood samples were collected after 48 h, 96 h, and 192 h of exposure. Hematological assay of exposed fish revealed abnormal mature and immature erythrocytes, deformed erythrocytes (spindle-shaped and triangular erythrocytes) and erythrocytes with segmented nuclei in all treatments. Arsenic exposure induced chromosomal aberration in a concentration-dependent manner, whereas, a decreasing trend was found after 192 h exposure. Observations on blood cells of exposed fish revealed chromosome breaks, chromatid breaks, and chromatid gaps. The alterations and aberrations of these parameters can be effectively used to assess toxicological effects of As on fish in the aquatic environment and at the same time this study elucidates the potential risks to humans who live in arsenic-contaminated areas.     

Somatostatin down-regulates the expression and release of endozepines from cultured rat astrocytes via distinct receptor subtypes

Endozepines, a family of regulatory peptides related to diazepam-binding inhibitor (DBI), are synthesized and released by astroglial cells. Because rat astrocytes express various subtypes of somatostatin receptors (sst), we have investigated the effect of somatostatin on DBI mRNA level and endozepine secretion in rat astrocytes in secondary culture. Somatostatin reduced in a concentration-dependent manner the level of DBI mRNA in cultured astrocytes. This inhibitory effect was mimicked by the selective sst4 receptor agonist L803-087 but not by the selective sst1, sst2 and sst3 receptor agonists L779-591, L779-976 and L797-778, respectively. Somatostatin was unable to further reduce DBI mRNA level in the presence of the MEK inhibitor U0126. Somatostatin and the sst1, sst2 and sst4 receptor agonists induced a concentration-dependent inhibition of endozepine release. Somatostatin and the sst1, sst2 and sst4 receptor agonists also inhibited cAMP formation dose-dependently. In addition, somatostatin reduced forskolin-induced endozepine release. H89 mimicked the inhibitory effect of somatostatin on endozepine secretion. In contrast the PLC inhibitor U73122, the PKC activator PMA and the PKC inhibitor calphostin C had no effect on somatostatin-induced inhibition of endozepine release. The present data demonstrate that somatostatin reduces DBI mRNA level mainly through activation of sst4 receptors negatively coupled to the MAPK pathway, and inhibits endozepine release through activation of sst1, sst2 and sst4 receptors negatively coupled to the adenylyl cyclase/PKA pathway.     

In vivo and in vitro management of Meloidogyne incognita (Tylenchida: Heteroderidae) using rhizosphere bacteria,Pseudomonas spp. and Serratia spp. compared with oxamyl

Biological control using rhizosphere bacteria, Pseudomonas spp. and Serratia spp. is a prospective alternative technique to overcome plant parasitic nematodes infection. So, the current study was conducted in vitro on five egg-masses, 100 free eggs and 100 infective juveniles (IJs) of Meloidogyne incognita as well as greenhouse treatments on Luffa aegyptiaca L. to evaluate the nematicidal potential of six strains belong to Pseudomonas spp. and Serratia spp. as compared to oxamyl.Results showed that the inhibitory effect and juvenile mortality varied according to bacteria species, strains and exposure time. All the tested bacteria significantly (P ≤ 0.05) inhibited egg hatching and increased juvenile mortality in vitro. After 3 days of treatment, Pseudomonas spp. were more effective against eggs (48.31to 55.15%) and IJs (20.98 to 25.30%) than Serratia spp. (44.55 to 49.75% with eggs) and (19.06 to 21.61% with IJs), respectively. In the pot experiment, Luffa aegyptiaca L. treated with Serratia spp. and Pseudomonas spp. displayed significantly higher (P ≤ 0.05) levels of growth (as indicated by root length, fresh roots weight and fresh shoots weight) compared to control plants and significantly (P ≤ 0.05) suppressed galling (number of galls) and reproduction (as indicated by number of egg-masses on roots and number of eggs and juveniles in pot soil). Meanwhile, among the treated plants, Serratia spp. and Pseudomonas spp. gave the best results in shoot weight of pots infected by eggs of M. incognita than those infected with IJs as compared with positive control. While, oxamyl treatment gave the best results in pots infected by eggs and IJs.The lowest galling (gall index), number of eggs and juveniles in soil was observed in the treatment with mixture of Serratia spp. and Pseudomonas spp. as well as, enhanced growth of sponge gourd more than application each of them alone. Pots treated with oxamyl overwhelmed those treated with mixture of Serratia spp. and Pseudomonas spp.     

Catalase and Lipid Peroxidation Values in Serum of Tunisian Patients with Pemphigus Vulgaris and Foliaceus

Pemphigus is an autoimmune disorder resulting from the interaction between autoantibodies and desmoglein. Oxidative stress seems to be responsible for the onset/aggravation of many human diseases. Actually, it is considered as one of the several factors for the etiopathogenesis of pemphigus. The present study aims to evaluate the oxidative state in the sera of pemphigus vulgaris and pemphigus foliaceus patients by assessing lipid peroxidation, proteins oxidation, and antioxidant enzyme activity. This study included 36 pemphigus vulgaris and 42 pemphigus foliaceus patients as well as a group of controls consisting of 78 healthy volunteers. Malondialdehyde levels (p?<?0.001) and catalase activity (p?<?0.001) are higher in both groups of patients than in the control group. The two groups of patients showed a nonsignificant decrease in the thiol groups compared with the healthy one. A nonsignificant difference was shown between pemphigus vulgaris and pemphigus foliaceus patients, except for the catalase which shows an increase in the pemphigus vulgaris group. We have also found significant correlations between serum oxidative stress marker levels and serum anti-desmoglein antibody levels in the two pemphigus groups. These findings underline the implication of oxidative stress in the physiopathology of pemphigus by the increase in the autoantibodies?? reactivity.     

Detection of common mutations in the GALT gene through ARMS

Type I galactosemia is an inborn error resulting from mutations on both alleles of the GALT gene, which leads to the absence or deficiency of galactose-1-phosphate uridyltranseferase (GALT), the second of three enzymes catalyzing the conversion of galactose into glucose. On the basis of residual GALT activity, Type I galactosemia is classified into severe “Classical” and mild “Duarte” phenotypes. Classical galactosemia is frequently associated with S135L, Q188R and K285N mutations in the GALT gene. The functionally neutral N314D variation in the GALT gene is associated with Duarte galactosemia and is widespread among various worldwide populations. The present study aimed at detecting S135L, Q188R and K285N mutations and the N314D variant in the GALT gene by PCR using amplification refractory mutation system (ARMS). ARMS assays were established using standard DNA samples and were used for 8 galactosemia patients and 190 unrelated normal subjects all of Pakistani origin. S135L and K285N mutations were present neither in galactosemia patients nor in normal subjects. Only one galactosemia patient carried Q188R mutation that was in homozygous state. However, the N314D variant was frequently found both in affected (7 out of 16 alleles) and normal subjects (55 out of 380 alleles). This finding indicates that Duarte allele D314 might be far more common in Pakistani population than in European and North American ones.