Genetic dissection of partial resistance to race 6 of Venturia inaequalis in apple.

Scab, caused by the fungus Venturia inaequalis, is one of the most important diseases of apple (Malus x domestica). The major resistance gene, Vf, has been widely used in apple breeding programs, but two new races of the fungus (races 6 and 7) are able to overcome this gene. A mapped F1 progeny derived from a cross between the cultivars Prima and Fiesta has bee n inoculated with two monoconidial strains of race 6. These strains originated from sporulating leaves of 'Prima' and a descendant of 'Prima' that were grown in an orchard in northern Germany. 'Prima' carries the Vf resistance gene, whereas 'Fiesta' lacks Vf. A large variation in resistance and (or) susceptibility was observed among the individuals of the progeny. Several quantitative trait loci (QTLs) for resistance were identified that mapped on four genomic regions. One of them was located in the very close vicinity of the Vf resistance gene on linkage group LG-1 of the 'Prima' genetic map. This QTL is isolate specific because it was only detected with one of the two isolates. Two out of the three other genomic regions were identified with both isolates (LG-11 and LG-17). On LG-11, a QTL effect was detected in both parents. The genetic dissection of this QTL indicated a favourable intra-locus interaction between some parental alleles.     

Differential association of membrane-bound and non-membrane-bound polysomes with the cytoskeleton

We report here a differential release of specific mRNAs from the cytoskeleton by cytochalasin D treatment. Non-membrane-bound polysomal mRNAs, such as histone mRNA and c-fos mRNA, are readily released from the cytoskeleton of HeLa cells during cytochalasin D treatment. Over 90% of H3 and H4 histone mRNA is associated with the cytoskeleton in control cells and only 25% in cells treated with cytochalasin D (40 micrograms/ml). In contrast, the membrane-bound polysomal mRNAs for HLA-B7 and chorionic gonadotropin-alpha are inefficiently released from the cytoskeletal framework by cytochalasin D alone; approximately 98% of the HLA-B7 mRNA in control cells is associated with the cytoskeleton, whereas approximately 65% of the HLA-B7 mRNA is retained on the cytoskeleton in cells treated with cytochalasin D (40 micrograms/ml). Disruption of polysome structure with puromycin during cytochalasin D treatment results in the efficient release of HLA-B7 mRNA from the cytoskeleton. Under these conditions, only 25% of the HLA-B7 mRNA remains associated with the cytoskeletal framework. Thus, membrane-bound polysomes appear to be attached to the cytoskeleton through a cytochalasin D-sensitive site as well as through association with the nascent polypeptide and/or ribosome. These results demonstrate a complex association of polysomes with the cytoskeleton and elements of the endoplasmic reticulum.     

Immunohistochemical detection of c-fos proteins in cultured human glial cells — induction by cyclic AMP and phorbol ester

Summary The expression of c-fos protein in cultured human glial cells derived from the brain and spinal cord was investigated immunocytochemically. Primary cultures of fetal glial cells were maintained in culture for three weeks and deprived of animal sera for 22 h. The glial cell nature of the cells was ascertained by GFAP-immunoreactivity. Incubations with phorbol dibutyrate, 8-Br-cAMP and sodium nitroprusside representing signal transduction pathways of PKC, PKA and cyclic GMP kinase, respectively, were carried out for 60 and 120 min. The control serum-deprived cultures did not display c-fos protein immunoreactivity (c-fos-IR), whereas phobol dibutyrate incubation for 120 min induced strong c-fos-IR in the nuclei of both brain and spinal cord derived glial cells. Semiquantitative intensity measurements revealed a slight c-fos-IR induction after 8-Br-cAMP as well, but not after sodium nitroprusside. The observations suggest that c-fos protein is involved in PKC and PKA signal transduction in cultured human glial cells.