Cadmium Tolerance and Accumulation in Indian Mustard Is Enhanced by Overexpressing γ-Glutamylcysteine Synthetase

To investigate rate-limiting factors for glutathione and phytochelatin (PC) production and the importance of these compounds for heavy metal tolerance, Indian mustard (Brassica juncea) was genetically engineered to overexpress the Escherichia coli gshI gene encoding γ-glutamylcysteine synthetase (γ-ECS), targeted to the plastids. The γ-ECS transgenic seedlings showed increased tolerance to Cd and had higher concentrations of PCs, γ-GluCys, glutathione, and total non-protein thiols compared with wild-type (WT) seedlings. When tested in a hydroponic system, γ-ECS mature plants accumulated more Cd than WT plants: shoot Cd concentrations were 40% to 90% higher. In spite of their higher tissue Cd concentration, the γ-ECS plants grew better in the presence of Cd than WT. We conclude that overexpression of γ-ECS increases biosynthesis of glutathione and PCs, which in turn enhances Cd tolerance and accumulation. Thus, overexpression of γ-ECS appears to be a promising strategy for the production of plants with superior heavy metal phytoremediation capacity.     

A novel, specific interaction involving the Csk SH3 domain and its natural ligand.

C-terminal Src kinase (Csk) takes part in a highly specific, high affinity interaction via its Src homology 3 (SH3) domain with the proline-enriched tyrosine phosphatase PEP in hematopoietic cells. The solution structure of the Csk-SH3 domain in complex with a 25-residue peptide from the Pro/Glu/Ser/Thr-rich (PEST) domain of PEP reveals the basis for this specific peptide recognition motif involving an SH3 domain. Three residues, Ala 40, Thr 42 and Lys 43, in the SH3 domain of Csk specifically recognize two hydrophobic residues, Ile 625 and Val 626, in the proline-rich sequence of the PEST domain of PEP. These two residues are C-terminal to the conventional proline-rich SH3 domain recognition sequence of PEP. This interaction is required in addition to the classic polyproline helix (PPII) recognition by the Csk-SH3 domain for the association between Csk and PEP in vivo. NMR relaxation analysis suggests that Csk-SH3 has different dynamic properties in the various subsites important for peptide recognition.     

Polyamine deficiency alters EGF receptor distribution and signaling effectiveness in IEC-6 cells

Cell growth andmigration are essential processes for the differentiation, maintenance,and repair of the intestinal epithelium. Epidermal growth factor (EGF)is an important factor in the reorganization of the cytoskeletonrequired for both processes. Because we had previously foundsignificant changes in the cytoskeleton during polyamine deficiency, itwas of interest to know whether those changes could prevent EGF fromstimulating growth and migration. Polyamine biosynthesis in IEC-6 cellswas interrupted by treatment with -difluoromethylornithine (DFMO), aspecific inhibitor of ornithine decarboxylase, the primaryrate-limiting enzyme of polyamine biosynthesis. DFMO halted cellproliferation and inhibited cell migration, and neither function couldbe normally stimulated by EGF. Immunocytochemistry of the transferrinreceptor (used as a marker for the endocytic pathway) revealed anabnormal distribution of the EGF receptor (EGFR) 10 min after bindingEGF. Polyamine deficiency depleted the cells of interiormicrofilaments, thickened the actin cortex, and prevented the promptassociation of EGF-bound EGFR with actin. EGF-stimulated 170-kDaprotein tyrosine phosphorylation and the kinase activity of purifiedmembrane EGFR were reduced by 50%. Immunoprecipatated EGFR proteinconcentration, however, was not reduced by polyamine deficiency. All ofthese changes could be prevented by supplementation with putrescine.Cytoskeletal disruption, reduced EGFR phosphorylation and kinaseactivity, aberrant intracellular EGFR distribution, and delayedassociation with actin filaments suggest a partial explanation for thedependence of epithelial cell growth and migration on polyamines.

     

Elaboration of enzymes in the digestive gland of Viviparus bengalensis (Mollusca: Gastropoda) during the first hours of digestion

digestive gland in Viviparus bengalensis does not show prominent rhythmicity in enzyme secretion during the post-feeding period. Amylolytic, lipolytic and proteolytic enzymes are secreted at a slightly enhanced rate between the first and second hour after feeding, which is followed by gradual decline to become more or less constant. The secretion of different enzymes is synchronous. The absence of secretory rhythms during post-feeding period appears to be correlated with food-habits and feeding behaviour.     

Fine needle aspiration of pulmonary adiaspiromycosis: a case report

BACKGROUND: Pulmonary adiaspiromycosis is a common disease of many species of wild rodents and occasionally of humans, caused by the inhalation of spores of the fungus Chrysosporium parvum var crescens (Emmonsia crescens). CASE: A 74-year-old female with pulmonary adiaspiromycosis was diagnosed by radiologically guided lung fine needle aspiration (FNA). The specimen showed intracellular and extracellular 100-300 microm conidia with a distinct thick, trilaminar wall, which was positive for Gomori-methenamine silver and periodic acid-Schiff stain. The background consisted of a granulomatous process. CONCLUSION: FNA is an effective method of diagnosing pulmonary adiaspiromycosis, and pathologists need to be aware of the characteristic features of this unusual opportunistic fungal infection.     

Comparison of CMV, RSV, SV40 viral and Vlambda1 cellular promoters in B and T lymphoid and non-lymphoid cell lines.

Determining the activity of viral and cellular regulatory elements in B or T lymphoid cell lines would facilitate appropriate utilization of the regulatory sequences for gene transfer- and expression-dependent applications. We have compared the activity of the CMV, RSV and SV40 viral promoter/enhancers as well as the Vlambda1 cellular promoter, in three B cell lines (REH, SMS-SB, C3P), three T cell lines (CEM, Jurkat, ST-F10), and two non-lymphoid cell lines (K-562, HeLa) using the luciferase reporter gene. In B cell lines, the activity of the CMV promoter/enhancer construct was the highest ranging from 10- to 113-fold greater than that of SV40. In contrast, in T cell lines the RSV promoter/enhancer activity was 11-65-fold higher than that of SV40. The Vlambda1 promoter activity was close to that of SV40 promoter/enhancer in most of the cell lines tested. We conclude that CMV and RSV promoter/enhancers contain stronger regulatory elements than do the SV40 and Vlambda1 for expression of genes in lymphoid cell lines.