ABSTRACT
Partial resistance quantitative trait loci (QTLs) Rphq11 and rphq16 against Puccinia hordei isolate 1.2.1 were previously mapped in seedlings of the mapping populations Steptoe/Morex and Oregon Wolfe Barleys, respectively. In this study, QTL mapping was performed at adult plant stage for the two mapping populations challenged with the same rust isolate. The results suggest that Rphq11 and rphq16 are effective only at seedling stage, and not at adult plant stage. The cloning of several genes responsible for partial resistance of barley to P. hordei will allow elucidation of the molecular basis of this type of plant defence. A map-based cloning approach requires to fine-map the QTL in a narrow genetic window. In this study, Rphq11 and rphq16 were fine-mapped using an approach aiming at speeding up the development of plant material and simplifying its evaluation. The plant materials for fine-mapping were identified from early plant materials developed to produce QTL-NILs. The material was first selected to carry the targeted QTL in heterozygous condition and susceptibility alleles at other resistance QTLs in homozygous condition. This strategy took four to five generations to obtain fixed QTL recombinants (i.e., homozygous resistant at the Rphq11 or rphq16 QTL alleles, homozygous susceptible at the non-targeted QTL alleles). In less than 2 years, Rphq11 was fine-mapped into a 0.2-cM genetic interval and a 1.4-cM genetic interval for rphq16. The strongest candidate gene for Rphq11 is a phospholipid hydroperoxide glutathione peroxidase. Thus far, no candidate gene was identified for rphq16.
ABSTRACT
We report the third case of spontaneous monochorionic dizygous pregnancy, discovered on foetal sex discordance. Blood group testing on the female twin revealed a hematopoietic chimera. The mechanism of monochorionic dizygous formation could be the fusion of two independent zygotes at a late morula stage. A single placental mass with vascular anastomosis then develops. Stem cells exchanged during early foetal life can thus lead to chimeras, in similar conditions to stem cell transfusion in adults. Immaturity of the foetal immune system allows cell graft in the other twin's marrow. Assisted reproductive procedures are believed to promote such pregnancies.
Subject(s)
Chimerism , Pregnancy Complications , Pregnancy, Multiple , Adult , Female , Humans , PregnancyABSTRACT
The transcription start point of the dnaK operon of Streptomyces coelicolor A3(2) has been determined by S1 mapping, using the EMBL automated fluorescent DNA sequencer. The -35 and -10 hexamers correspond to a sigma 70-type promoter. This promoter responds to heat shock and involves an inverted repeat different from the CIRCE sequence characteristic of the Gram-positive heat-shock promoters.
Subject(s)
Operon/genetics , Sequence Analysis, DNA/methods , Streptomyces/genetics , Transcription, Genetic/genetics , Base Sequence , Chromosome Mapping , Gene Expression Regulation, Bacterial/physiology , Genes, Bacterial/genetics , Heat-Shock Proteins/genetics , Molecular Sequence Data , Plasmids , Polymerase Chain Reaction , Promoter Regions, Genetic/genetics , Recombinant Proteins/geneticsABSTRACT
The dnaK operon of Streptomyces coelicolor A3(2) was cloned by the DNA-probing method using synthetic oligonucleotides designed on the basis of two of the most conserved regions in 30 different DnaK proteins (HSP70). The isolated insert-a BamHI 5.6-kb fragment-was sequenced and shown to contain three open-reading frames organized in an operon and coding for proteins analogous to DnaK, GrpE and DnaJ, successively.