Cosntruction of the physical map of yeast（Saccharomyces cerevisiae）chromosome V~1

There are about 17 chromosomes in yeast Saccharomycescerevisiae.A middle sized chromosome,chromosome V,waschosen in this work for studying and constructing the physi-cal maps.Chromosome V from strain A364a was isolatedby pulsed-field gradient gel electrophoresis(PFGE).Gelslices containing chromosome V DNA were digestedwith two rare cutting enzymes,NotⅠand SfiⅠ,and three6-Nt recognizing enzymes,SmaⅠ,SstⅡ and ApaⅠ.Several strategies-partial or complete digestions,digestion with different sets of two enzymes,and hybrid-ization with cloned genetically mapped probes(CAN1,URA3,CEN5,PRO3,CHO1,SUP19,RAD51,RAD3)——were used to align the restriction fragments.There are 9,9,15,17,and 20 sites for NotⅠ,SfiⅠ,SmaⅠ,SstⅡ and ApaⅠrespectively in the map of the A364a chromosome V.Itstotal length was calculated to be 620 Kb(Kilo-bases).Thedistributions of the cutting sites for these five enzymesthrough the whole chromosome are not uniform.A comp-arison between the physical map and the genetic map wasalso made.     

The synthesis and use of the owl’s auditory space map

The barn owl (Tyto alba) is capable of capturing prey by passive hearing alone, guided by a topographic map of auditory space in the external nucleus of its inferior colliculus. The neurons of this auditory space map have discrete spatial receptive fields that result from the computation of interaural differences in the level (ILD) and time-of-arrival (ITD) of sounds. Below we review the synthesis of the spatial receptive fields from the frequency-specific ITDs and ILDs to which the neurons are tuned, concentrating on recent studies exploiting virtual auditory space techniques to analyze the contribution of ILD. We then compared the owls spatial discrimination, assessed behaviorally, with that of its space map neurons. Spatial discrimination was assessed using a novel paradigm involving the pupillary dilation response (PDR), and neuronal acuity was assessed by measuring the changes in firing rate resulting from changes in source location, scaled to the variance. This signal-detection-based approach revealed that the change in the position of the neural image on this map best explains the spatial discrimination measured using the PDR. We compare this result to recent studies in mammalian systems.     

A genetic linkage map of the cultivated strawberry (Fragaria × ananassa) and its comparison to the diploid Fragaria reference map

The cultivated strawberry, Fragaria × ananassa, is the most economically-important soft-fruit species, but few practical molecular tools for the purpose of marker assisted selection currently exist. As a precursor to the development of such tools, a genetic linkage map was developed from a F₁ population comprising 174 seedlings derived from a cross between two F. × ananassa cultivars, ‘Redgauntlet’ × ‘Hapil’. The resultant map is composed of 315 molecular markers—218 microsatellites, 11 gene-specific markers and 86 AFLP and RAPD markers—and spans 3,116 cM. In total, 69 linkage group fragments were recovered, more than the 56 linkage groups expected for the cultivated strawberry, however, all fragments contained a transferable marker that could be associated with one of 56 linkage group scaffolds. The female (Redgauntlet) and male (Hapil) linkage maps are composed, respectively of 170 loci in 32 linkage groups covering 1,675.3 cM and 182 loci in 37 linkage groups covering 1,440.7 cM, with 37 markers common to both maps. The maximum number of markers in one linkage group was 15, the minimum was two. All linkage groups resolved contained at least one transferable marker (SSR or gene-specific) that had been mapped on the diploid Fragaria reference map (FV × FB), and therefore all linkage groups could be identified as homologous to one of the seven diploid Fragaria linkage groups. When marker order was compared to the diploid Fragaria reference map, effectively complete colinearity was observed. However, the occurrence of duplicated loci on homologues of linkage groups FG1 and FG6 provided evidence of a putative chromosomal duplication or translocation event in Fragaria. The development of this linkage map will facilitate the study and dissection of QTL associated with traits of economic importance such as disease resistance and fruit quality, and provides a foundation for the development of markers for the purpose of marker assisted breeding and selection in the cultivated strawberry, F. × ananassa.     

Virus ecology of fluvial systems: a blank spot on the map?

The ecology of viruses has been studied only in a limited number of rivers and streams. In light of a recent re‐appraisal of the global fluvial surface area, issues such as abundance and production, host mortality and the influence of suspended particles and biofilms are addressed. Viral life cycles, potential impacts of viruses on water biochemistry and carbon flow, and viral diversity are considered. Variability in trophic levels along with the heterogeneous nature and hydrological dynamics of fluvial environments suggest a prevailingly physical control of virus‐related processes under lotic conditions and more biological control under lentic conditions. Viral lysis likely contributes to a pool of rapidly cycling carbon in environments typically characterized by high proportions of recalcitrant terrestrial carbon. On average, 33.6% (equalling 0.605 Pg C year^?1) of the globally respired carbon from fluvial systems may pass through a viral loop. Virus distribution and the proportion of organic material in horizontal transport versus processes in retention zones remain to be determined in detail. The need for up‐scaling the contribution of virus‐related processes in fluvial systems is of global relevance. Further, the role of climate change and the effect of anthropogenic alterations of fluvial systems on viruses require attention. The identification of these considerable knowledge gaps should foster future research efforts.     

Structure-function map of the receptor site for β-scorpion toxins in domain II of voltage-gated sodium channels

Voltage-gated sodium (Na(v)) channels are the molecular targets of β-scorpion toxins, which shift the voltage dependence of activation to more negative membrane potentials by a voltage sensor-trapping mechanism. Molecular determinants of β-scorpion toxin (CssIV) binding and action on rat brain sodium channels are located in the S1-S2 (IIS1-S2) and S3-S4 (IIS3-S4) extracellular linkers of the voltage-sensing module in domain II. In IIS1-S2, mutations of two amino acid residues (Glu(779) and Pro(782)) significantly altered the toxin effect by reducing binding affinity. In IIS3-S4, six positions surrounding the key binding determinant, Gly(845), define a hot spot of high-impact residues. Two of these substitutions (A841N and L846A) reduced voltage sensor trapping. The other three substitutions (N842R, V843A, and E844N) increased voltage sensor trapping. These bidirectional effects suggest that the IIS3-S4 loop plays a primary role in determining both toxin affinity and efficacy. A high resolution molecular model constructed with the Rosetta-Membrane modeling system reveals interactions of amino acid residues in sodium channels that are crucial for toxin action with residues in CssIV that are required for its effects. In this model, the wedge-shaped CssIV inserts between the IIS1-S2 and IIS3-S4 loops of the voltage sensor, placing key amino acid residues in position to interact with binding partners in these extracellular loops. These results provide new molecular insights into the voltage sensor-trapping model of toxin action and further define the molecular requirements for the development of antagonists that can prevent or reverse toxicity of scorpion toxins.     

Expanding the genetic map of maize with the intermated B73 × Mo17 (IBM) population

The effects of intermating on recombination and the development of linkage maps were assessed in maize. Progeny derived from a common population (B73 × Mo17) before and after five generations of intermating were genotyped at the same set of 190 RFLP loci. Intermating resulted in nearly a four-fold increase in the genetic map distance and increased the potential for improved genetic resolution in 91% of the intervals evaluated. This mapping population and related information should connect research involving dense genetic maps, physical mapping, gene isolation, comparative genomics, analysis of quantitative trait loci and investigations of heterosis.     

An update of the Courtot × Chinese Spring intervarietal molecular marker linkage map for the QTL detection of agronomic traits in wheat

We made an update of the intervarietal molecular marker linkage map of the wheat genome developed using a doubled-haploid (DH) population derived from the cross between the cultivars "Courtot" and "Chinese Spring". This map was constructed using 187 DH lines and 659 markers. The genome was well covered (more than 95%) except for chromosomes from homoeologous group 4 and chromosomes 5D and 7D, which had gaps slightly larger than 50 cM. A core-map based on a set of 200 anchor loci (one marker each 18.4 cM) was developed. The total length of this map was 3,685 cM which is similar to the size of the international reference map of the ITMI population (3,551 cM). Map coverage was identical for the three genomes (A, B and D) and for the number of anchor loci, as well as for the size of the map. Using this map, QTLs for several agronomic traits were detected on phenotypic data from the population grown in Clermont-Ferrand (France) under natural field conditions over 6 years, and in Norwich (UK) in controlled conditions and under natural field conditions in 1 year. Almost all of the 21 chromosomes were involved in at least one trait. However, several regions seemed to contain gene clusters either for grain traits (and thus bread-making quality) or plant development traits.     

Recombination hot spots within the I region of the mouse H-2 complex map to the E β and E α genes

Recombinant mouse strains with crossovers in the I region of the H-2 major histocompatibility complex were examined by restriction fragment analysis for the presence of polymorphic restriction sites within the E and E genes. Nine recombinant mouse strains were shown to have crossed over within a 5 kb DNA segment that contains the large intron between the second and third exons of the E gene. These results are in accord with previous studies mapping a recombination hot spot within this gene. Seven recombinant mouse strains between the p and k haplotypes were shown to have crossed over in a 6 kb segment within the E gene. These results show the existence of a recombination hot spot within the E gene. Comparison of the H-2 haplotypes involved in these two recombination hot spots suggests that a specific DNA sequence in b, s, f, and q haplotypes may act to promote recombination in the E gene and a specific DNA sequence in the p haplotype may act to promote recombination in the E gene.