Molecular cloning and characterization of a phytochelatin synthase gene, PvPCS1, from Pteris vittata L.

Pteris vittata L. is a staggeringly efficient arsenic hyperaccumulator that has been shown to be capable of accumulating up to 23,000 microg arsenic g(-1), and thus represents a species that may fully exploit the adaptive potential of plants to toxic metals. However, the molecular mechanisms of adaptation to toxic metal tolerance and hyperaccumulation remain unknown, and P. vittata genes related to metal detoxification have not yet been identified. Here, we report the isolation of a full-length cDNA sequence encoding a phytochelatin synthase (PCS) from P. vittata. The cDNA, designated PvPCS1, predicts a protein of 512 amino acids with a molecular weight of 56.9 kDa. Homology analysis of the PvPCS1 nucleotide sequence revealed that it has low identity with most known plant PCS genes except AyPCS1, and the homology is largely confined to two highly conserved regions near the 5'-end, where the similarity is as high as 85-95%. The amino acid sequence of PvPCS1 contains two Cys-Cys motifs and 12 single Cys, only 4 of which (Cys-56, Cys-90/91, and Cys-109) in the N-terminal half of the protein are conserved in other known PCS polypeptides. When expressed in Saccharomyces cerevisae, PvPCS1 mediated increased Cd tolerance. Cloning of the PCS gene from an arsenic hyperaccumulator may provide information that will help further our understanding of the genetic basis underlying toxic metal tolerance and hyperaccumulation.     

Direct analysis of thymic function in children with Down's syndrome

BACKGROUND: Down's syndrome (DS) is characterized by several immunological defects, especially regarding T cell compartment. DS is considered the best example of accelerated ageing in humans. Direct observations of the thymus have shown that in DS this organ undergoes severe histological and morphological changes. However, no data on its capacity to generate T cells are present in the literature. Here, using a new technology based upon real time PCR, we have investigated the capacity of the thymus to produce and release newly generated T lymphocytes (the so called "recent thymic emigrants", RTE) in children with DS. METHODS: We studied 8 children affected by DS, aged 2-7 years, compared with 8 age- and sex-matched healthy controls. Flow cytometry was used to determine different lymphocytes subsets. Real time PCR with the Taqman system was used to quantify the amount of RTE, i.e. peripheral blood lymphocytes that express the T cell receptor rearrangement excision circles (TREC). RESULTS: In comparison with control children, those with DS had a significant lower number of TREC+ peripheral blood cells. Moreover, in DS children but not in controls, a strong negative correlation between age and the levels of TREC+ cells was found. CONCLUSIONS: The direct measure of thymic output indicates that the impairment of the organ results in a reduced production of newly generated T cells. This observation could suggest that cytokines able to modulate thymic function, such as interleukins, could be useful to improve the functionality of the organ and to treat the immunodeficiency present in DS subjects.     

Characterzation of chitinases able to rescue somatic embryos of the temperature-sensitive carrot variantts11

To characterize the acidic endochitinase EP3, able to rescue somatic embryos of the carrot cell linets11, the enzyme was purified from the medium of wild-type suspension cultures. Peptide sequences, deduced amino acid sequences of corresponding PCR-generated cDNA clones, serological relation and biochemical properties showed that there were at least five closely related chitinases, four of which could be identified as class IV EP3 chitinases with an apparent size of 30 kDa. Two other proteins were identified as a serologically related class I acidic chitinase (DcChitI) of 34 kDa, and a serologically unrelated 29 kDa class II acidic chitinase (DcChitII), respectively. Additional cDNA sequences, Western and Southern analysis showed the presence of a least two, but possibly more, highly homologous class IV EP3 genes in the carrot genome. Two class IV EP3 chitinases were tested and found to be able to increase the number ofts11 globular embryos formed under non-permissive conditions. One of the class IV EP3 chitinases as well as the class I chitinase DcChitI promoted the transition from globular to heart-stagets11 embryos. The class II endochitinase and a heterologous class IV chitinase from sugar-beet were not active onts11. This suggests that there are differences in the specificity of chitinases in terms of their effect on plant somatic embryos.     

Non-random chromosomal aberrations in a complex leukaemic clone of a Bloom's syndrome patient

Summary Bloom's syndrome is one of the congenital disorders known to have increased frequency of acute leukaemia. The complex cytogenetic findings in the leukaemic cells of a 39-year-old male with Bloom's syndrome are described. These included a translocation t(7;17), missing 7q and 17p, a reciprocal translocation t(4;22); del 3q, del 8q22, del 20q, missing 12 and missing Y. In the same patient a missing Y had been noted 10 years previously in 15% of his peripheral blood lymphocytes.     

Stop the killer: how to inhibit the anthrax lethal factor metalloprotease

Inhalation of anthrax spores rapidly develops into a deadly bacteraemia and toxaemia. Anthrax toxins include the lethal factor (LF), a mitogen-activated protein kinase (MAPK)-kinase-specific metalloprotease, which acts in the cell cytosol and plays a major part in anthrax pathogenesis. Recently, screening methods have led to the discovery of LF inhibitors that are membrane permeable. This will pave the way for design of novel anthrax therapeutics that are capable of inhibiting the metalloprotease activity of LF in vivo.