Penetration and early colonization in basidiospore-derived infection of Melampsora pulcherrima (Bub.) Maire on Mercurialis annua L.

SUMMARYThe early phases of basidiospore-derived infection of Melampsora pulcherrima (Bub.) Maire on the leaves of Mercurialis annua L. were studied by light microscopy, SEM and TEM. The fine morphology of the basidiospore germling penetration and intraepidermal infection structures is discussed in comparison with that of other rusts recently described. The direct penetration through the epidermal cell wall, characteristic of the rust basidiospore-derived germlings, is confirmed. The absence of an extrahyphal matrix around the intraepidermal vesicle and the presence of a collar around the vesicle neck are pointed out

Signs of resistance to Melampsora larici-tremulae on species of Pinus hosts of Melampsora pinitorqua: implications regarding the taxonomic relationship between the two rust fungi

Signs of resistance such as cortical necroses which occurred after artificial inoculations with Melampsora larici-tremulae on some species of the genus Pinus in the host range of M. pinitorqua were evaluated. Similar observations were carried out on P. sylvestris inoculated with two provenances of M. larici-tremulae from areas with different environmental conditions. In both experiments, the degree of resistance to M. larici-tremulae depended on how suitable environmental conditions were for both the host and the fungus. The greatest resistance to M. laricitremulae was shown by P. sylvestris.These observations could indicate that P. sylvestris is becoming a nonhost of M. larici-tremulae. The type of host-parasite interaction between some species of Pinus and M. larici-tremulae, when compared to analogous interactions between the same species of Pinus and M. pinitorqua, can shed light on the taxonomic relationship between the two rust fungi

Production of high-titer lentiviral particles for stable genetic modification of mammalian cells

Lentiviral gene transfer technologies exploit the natural efficiency of viral transduction to integrate exogenous genes into mammalian cells. This provides a simple research tool for inducing transgene expression or endogenous gene knockdown in both dividing and nondividing cells. This chapter describes an improved protocol for polyethylenimine (PEI)-mediated multi-plasmid transfection and polyethylene glycol (PEG) precipitation to generate and concentrate lentiviral vectors

The Wnt receptor FZD1 mediates chemoresistance in neuroblastoma through activation of the Wnt/beta-catenin pathway

The development of chemoresistance represents a major obstacle in the successful treatment of cancers such as neuroblastoma (NB), a particularly aggressive childhood solid tumour. The mechanisms underlying the chemoresistant phenotype in NB were addressed by gene expression profiling of two doxorubicin (DoxR)-resistant vs sensitive parental cell lines. Not surprisingly, the MDR1 gene was included in the identified upregulated genes, although the highest overexpressed transcript in both cell lines was the frizzled-1 Wnt receptor (FZD1) gene, an essential component of the Wnt/beta-catenin pathway. FZD1 upregulation in resistant variants was shown to mediate sustained activation of the Wnt/beta-catenin pathway as revealed by nuclear beta-catenin translocation and target genes transactivation. Interestingly, specific micro-adapted short hairpin RNA (shRNAmir)-mediated FZD1 silencing induced parallel strong decrease in the expression of MDR1, another beta-catenin target gene, revealing a complex, Wnt/beta-catenin-mediated implication of FZD1 in chemoresistance. The significant restoration of drug sensitivity in FZD1-silenced cells confirmed the FZD1-associated chemoresistance. RNA samples from 21 patient tumours (diagnosis and postchemotherapy), showed a highly significant FZD1 and/or MDR1 overexpression after treatment, underlining a role for FZD1-mediated Wnt/beta-catenin pathway in clinical chemoresistance. Our data represent the first implication of the Wnt/beta-catenin pathway in NB chemoresistance and identify potential new targets to treat aggressive and resistant NB