A genomic clone containing a telomere array maps near the centromere of mouse Chromosome 6

A lambda clone of mouse DNA containing a short array of telomere hexamers has been localized by FISH to a region close to the centromere of Chromosome (Chr) 6. Amplification of DNA with primers flanking an SSR showed that most inbred strains carry one of two alleles, although five other alleles were found among the inbred strains and 11 other alleles were found in wild-derived mice. Analysis of the DNA from four Robertsonian translocations suggests that the amplified sequence is still present in these chromosomes. The finding of two fragments associated with the Sig mutant suggests that the clone lies within a congenic region created when the mutant, obtained in a (C3H x 101)F₁, was back-crossed to C57BL/6J. This region might include all or part of the centromere. Comparison of the segregation of the amplification product with the segregation of centromeric heterochromatin in an interspecies backcross, (C57BL/6 x M. spretus)F₁ x M. spretus, (BSS) shows 1/72 recombinants with the centromeric heterochromatin, while 1/62 recombinants occurred in a BSB backcross. Analysis of other loci at the proximal end of Chr 6 gives the combined map Hc6-0.73-D6Mit86-0.73-D6Rp2-2.2-D6Mitl-2.2-Wnt2-3.0-Cpa. Data from a third cross show that Cola2 lies between D6Mit82 and D6Rp2. The portion of the telomere array, Tel-rs3, that has been sequenced contains only 13/31 repeats of the consensus sequence. A variety of sequence changes from the consensus hexamer suggests that this array has been removed for a long time from evolutionary pressures to retain the TTAGGG sequence.     

Analysis of genetic recombination in maize populations using molecular markers

Summary Variation in recombination rate is important to plant breeders since a major objective is to obtain favorable recombinants of linked genes. The ability to increase recombination (R) in circumstances in which favorable and unvavorable genes are linked (Corn Belt x exotic populations) and to decrease recombination when many favorable genes are linked (narrow-based, elite populations) would be of immense value. However, the concept of variation in recombination frequencies between linked genes has received limited attention despite its implications in breeding and genetic linkage studies. Molecular techniques have allowed better estimations of this variation. In this study, attempts were made to characterize: (1) the R values in the Pgm1-Adh1 and Adh1-Phi1 adjacent regions of chromosome 1 and the Idh2-Mdh2 region of chromosome 6 in F₂ families of three maize (Zea mays L.) populations; (2) the environmental effect on R values of F₂s from two populations. One population, NSO, was a Corn Belt synthetic, and the other two populations, CBMEX3 and CBCAR5, were composites from crosses between Corn Belt and exotic germ-plams.Wide ranges of estimated recombination ( ) values were observed among families in each population for all three chromsomal regions. The distribution of values for the Pgm1-Adh1 region showed that the F₂ families of each population fell into two broad categories: 0.30–0.50 and 0.02–0.20. No intermediates (0.21–0.29) were found. The distributions were almost normal for the Adh1-Phi1 and the Idh2-Mdh2 regions. It would appear that the major dispersion in the Pgm1-Adh1 region was controlled by the effects of a single gene, while the Adh1-Phi1 and Idh2-Mdh2 regions were only affected by polygenes. No correlation was found between recombination values of the two adjacent regions, indicating that the genes affecting recombination for the Pgm1-Adh1 region may be specific for that region.For the Pgm1-Adh1 region, no differences in values were found among the three populations. For the Adh1-Phi1 region, frequencies of CBMEX3 and NSO were not significantly different, but both had significantly greater values than CBCAR5. For the Idh2-Mdh2 region, CBMEX3 was significantly different from NSO. There were significant differences between some paired F₂ families within each population for each chromosome region.No significant differences in response to the two environments were detected in CBMEX3 and NSO for either region in chromosome 1.Published as Journal Paper No. 9498 of the Nebraska Agric Res Div, University of Nebraska, Lincoln, Neb. Research supported in part by USDA Competitive Grant 87-CRCR-2359     

Detection of wheat-alien recombinant chromosomes using co-dominant DNA markers**

A study of homoeologous recombination along almost the complete genetic length of two homoeologous chromosomes in the Triticeae was conducted. Sears' phlb mutant was used to induce homoeologous pairing between chromosomes 7A of common wheat and 7Ai–l of Agropyron intermedium. 390 ph1b ph1b homozygous F₃ progeny were screened using six co-dominant DNA markers (RFLP loci). 63 of the progeny (16%) were putative recombinants, showing dissociation of RFLP markers within the arm(s). Progeny tests of self-fertile putative recombinants confirmed the dissociation phenotypes observed in the F₃ progeny. No recombination could be confirmed in 117 F₃ progeny plants having the Ph1– allele (control population). Frequencies and distribution of chiasmata along the chromosome arm 7AS were analysed using additional RFLP markers. The patterns of recombination between the two homoeologous chromosomes were found similar to those reported for homologous recombination between the same markers on short arms of group 7 chromosomes of Triticeae.     

Recombination between kappa chain genetic markers in the mouse

In this study we report the first instance of recombination between kappa chain genetic markers in the mouse. The recombination frequency, 0.45% (95% limits, 0.12–1.61), is similar to that previously found for recombination between the kappa chain locus and the Lyt-2, 3 locus (0.3%, 95% limits, 0.05–1.6), but is relatively low in comparison with that found at the heavy chain locus (0.41–5.4%). Lyt-2, 3-typing of the recombinants permits a partial ordering of the kappa chain and Lyt-2, 3 loci as (Lyt-2, 3, Igk-Ef1) - Igk-Ef2. Light chains controlled by the two kappa markers include the V_k-(ser) subgroup (controlled by Igk-Ef1) and V_k–1 (controlled by Igk-Ef2). One of the recombinants has been recovered in a homozygous state (NAK) and should be suitable for V _k gene mapping studies.Abbreviations C complement - C_H constant region of the Ig heavy chain - CI cytotoxicity index - DNP dinitrophenyl - FMF flow microfluorimetry - IEF isoelectric focusing - IF immunofluorescence - Ig immunoglobulin - KLH keyhole limpet hemocyanin - V_H variable region of the Ig heavy chain - V_k variable region of the Ig kappa chain - V-region variable region     

Genomic assignment of the warfarin resistance locus, Rw, in the rat

The locus responsible for resistance to the anticoagulants warfarin and bromadiolone (locus symbol Rw) was integrated into the rat (Rattus norvegicus) microsatellite genome map. Seventh-generation offspring of a segregating strain of rats heterozygous resistant to both compounds were tested with a blood-clotting-response (BCR) test. No recombination between resistance to warfarin and bromadiolone was observed, indicating a common genetic basis. No recombinants were found between Rw and D1Arb18 (Myl2) located at the MIT-microsatellite map position 95.90 (SHRSP × BN F₂-cross) or 82.24 (FHH × ACI F₂-cross). Resistance segregated in a ratio expected for single, dominant gene responses. An equal number of females and males were resistant, but females retained higher percentage blood coagulation activities (PCA) after anticoagulant administration. Partial synteny between rat, mouse, and human suggests that Myl2 may serve as anchor to map the Rw homologs in mouse and human. Received: 30 December 1998 / Accepted: 17 March 1999     

Influence of edeine on intergenic and interallelic recombination in Neurospora crassa

Summary The effect of edeine and the mutation ed ^r-2 to edeine resistance on genetic recombination in Neurospora crassa was investigated. For this purpose crosses between pairs of edeine sensitive and edeine resistant strains respectively were set up without or in the presence of the drug (0–750 g/ml). The genetic markers ylo-1, ad-1, pan-2 (B ₃ and B ₅) and tryp-2, all on linkage group VI, were used for scoring recombinants. These were ad ⁺, tryp ⁺ (intergenic recombination) and pan ⁺ (interallelic recombination).Frequencies of about 6–7% for intergenic and of about 0.4% for interallelic recombination were found in crosses between ed^s strains and ed^r strains respectively, if edeine was absent. However, crosses in the presence of edeine gave higher frequencies of both intergenic and interallelic recombination (about 12% intergenic and 1% interallelic with 180 to 200 g ed/ml).The pan⁺ prototrophs (interallelic recombinants) obtained in the different crosses were tested for distribution of outside markers. The data thus obtained revealed, that under the effect of both the mutation to edeine resistance and edeine itself the relative number of non-crossover (gene conversion) recombinants decrease in favour of crossover recombinants, and the relative number of double crossover recombinants (events outside the pan locus) decreases in favour of single crossover recombinants.It is concluded that a) edeine and the mutation ed ^r-2 to edeine resistance affect recombination via related pathways, and b) noncrossover and crossover recombinants are caused by different molecular mechanisms, in agreement with the work of other authors.     

Fine mapping of qhir1 influencing in vivo haploid induction in maize

Production of haploids by the in vivo haploid induction method has now become routine for generating new inbred lines in maize. In previous studies, a major quantitative trait locus (QTL) (qhir1) located in bin 1.04 was detected, explaining up to 66 % of the genotypic variance for haploid induction rate (HIR). Our objectives were to (1) fine-map qhir1 and (2) identify closely linked markers useful for marker-assisted breeding of new inducers. For this purpose, we screened a mapping population of 14,375 F₂ plants produced from a cross between haploid inducer UH400 and non-inducer line 1680 to identify recombinants. Based on sequence information from the B73 reference genome, markers polymorphic between the two parents were developed to conduct fine mapping with these recombinants. A progeny test mapping strategy was applied to accurately determine the HIR of the 14 recombinants identified. Furthermore, F₃ progeny of recombinant F₂ plants were genotyped and in parallel evaluated for HIR. We corroborated earlier studies in that qhir1 has both a significantly positive effect on HIR but also a strong selective disadvantage, as indicated by significant segregation distortion. Altogether, we were able to narrow down the qhir1 locus to a 243 kb region flanked by markers X291 and X263.     

Genetic studies of self-fertility in rye (Secale cereale L.). 2. The search for isozyme marker genes linked to self-incompatibility loci

The segregation of several isozyme marker genes has been studied in F₂ inbred families from hybrids between self-sterile and five self-fertile inbred lines (nos. 2, 3, 4, 5, and 8) as well as from interline hybrids. Self-pollination of F₁ hybrids between self-sterile forms and lines 5 and 8 gave an F₂ segregation ratio of 1 heterozygote:1 homozygote for the gene Prx7 (chromosome 1R) against the allele from the line. This is interpreted as a result of tight linkage of the Prx7 gene with the S1 gene in chromosome 1R (recombination at a level of 0–1%). The self-pollination of such hybrids with lines 2,3 and 4 gave normal segregation for the Prx7 gene (1:2:1). This means that these lines carry a self-fertility allele which is not on chromosome 1R. Interline hybrids 5×2, 5×3 and 5×4 had self-fertility alleles for the two S genes and in inbred F₂ progenies gave the expected deviating segregation for the Prx7 gene in a ratio of 2:3:1. The segregation of interline hybrid 5×8 was normal, 1:2:1, as expected. Highly-deviating segregation in an inbred F₂ family of a hybrid with line 5 has also been obtained for another gene from chromosome 1R — Pgi2 (recombination with the S1 locus of 16.7%). By using the same method it has been estimated that line 4 has a self-fertility allele of the S2 locus from chromosome 2R and that the genes -Glu and Est4/11 are linked with it (recombination 16.7% and 17.5–20% respectively). Lines 2 and 3 have a self-fertility allele of the S5 locus from chromosome 5R which is linked with the Est5-7 gene complex (recombination at a level of 28.8–36.0%).     

Ifg,Gli, Mdm1, Mdm2, and Mdm3: candidate genes for the mouse pg locus

Various genes that mapped to the distal end of Chromosome (Chr) 10 were considered as possible candidates for the mouse pygmy (pg) locus. Probes derived from Ifg, Gli, Mdm1, Mdm2 and Mdm3 (Mdm2 and Mdm3 are genes that are coamplified with Mdm1 on the same double minute chromosomes in 3T3DM cells) were used for Southern analysis of DNA from wild-type mice and various pg mutants. In addition, the chromosomal locations of Ifg, Gli, Mdm1, Mdm2, and Mdm3 were determined by interspecific backcross analysis with progeny derived from matings of [(C57BL/6J x Mus spretus)F₁ x C57BL/6J] mice. The mapping data indicate that the Mdm loci are linked to each other and to Ifg, pg, and Gli in the distal region of mouse Chr 10. Both the mapping data and the Southern analysis confirm that mdm1, Mdm2, Mdm3, Ifg, and Gli are distinct from pg.     

A major QTL for resistance to Gibberella stalk rot in maize

Fusarium graminearum Schwabe, the conidial form of Gibberella zeae, is the causal fungal pathogen responsible for Gibberella stalk rot of maize. Using a BC₁F₁ backcross mapping population derived from a cross between ‘1145’ (donor parent, completely resistant) and ‘Y331’ (recurrent parent, highly susceptible), two quantitative trait loci (QTLs), qRfg1 and qRfg2, conferring resistance to Gibberella stalk rot have been detected. The major QTL qRfg1 was further confirmed in the double haploid, F₂, BC₂F₁, and BC₃F₁ populations. Within a qRfg1 confidence interval, single/low-copy bacterial artificial chromosome sequences, anchored expressed sequence tags, and insertion/deletion polymorphisms, were exploited to develop 59 markers to saturate the qRfg1 region. A step by step narrowing-down strategy was adopted to pursue fine mapping of the qRfg1 locus. Recombinants within the qRfg1 region, screened from each backcross generation, were backcrossed to ‘Y331’ to produce the next backcross progenies. These progenies were individually genotyped and evaluated for resistance to Gibberella stalk rot. Significant (or no significant) difference in resistance reactions between homozygous and heterozygous genotypes in backcross progeny suggested presence (or absence) of qRfg1 in ‘1145’ donor fragments. The phenotypes were compared to sizes of donor fragments among recombinants to delimit the qRfg1 region. Sequential fine mapping of BC₄F₁ to BC₆F₁ generations enabled us to progressively refine the qRfg1 locus to a ~500-kb interval flanked by the markers SSR334 and SSR58. Meanwhile, resistance of qRfg1 to Gibberella stalk rot was also investigated in BC₃F₁ to BC₆F₁ generations. Once introgressed into the ‘Y331’ genome, the qRfg1 locus could steadily enhance the frequency of resistant plants by 32–43%. Hence, the qRfg1 locus was capable of improving maize resistance to Gibberella stalk rot.     

Na+-independent,electrogenic Cl- uptake across the posterior gills of the Chinese crab (Eriocheir sinensis): Voltage-clamp and microelectrode studies

Summary Single gill lamellae from posterior gills of Chinese crabs (Eriocheir sinensis) were isolated, separated into halves and mounted in a modified Ussing chamber. Area-related short-circuit current (I_sc) and conductance (G_tot) of this preparation were measured. Epithelial cells were impaled with microelectrodes through the basolateral membrane and cellular potentials (V_i under open- and V_sc under short-circuit conditions) as well as the voltage divider ratios (F_i, F_o) were determined.With NaCl salines on both sides an outside positive PD_te (22±2 mV) and an I_sc (-64±13 A·cm^-2) with a polarity corresponding to an uptake of negative charges (inward negative) were obtained. Trough-like potential profiles were recorded across the preparation under open- as well as short-circuit conditions (V_o=-101±5 mV, external bath as reference; V_i=-78±2 mV, internal bath as reference; V_sc=-80±2 mV, extracellular space as reference). The voltage divider ratios of the external (apical membrane plus cuticle) and internal (basolateral membrane) barrier were F_o=0.92±0.01 and F_i=0.08±0.01, respectively. To investigate a Cl^--related contribution to the above parameters, Na⁺-free solutions in the external bath (basolateral NaCl-saline) were used. Inward negative I_sc under these conditions almost completely depended on external Cl^-. Elimination of Cl^- in the external bath reversed I_sc, and G_tot decreased substantially. Concomitantly, V_sc depolarised and F_o increased. Cl^--dependent current and conductance showed saturation kinetics with increasing external [Cl^-]. Addition of 20 mmol·1^-1 thiocyanate to the external bath had similar, although less pronounced, effects as Cl^- substitution. Equally, external SITS (1 mmol·1^-1) inhibited the current and, concomitantly, G_tot decreased substantially. Addition of 1 mmol·1^-1 acetazolamide to, and omission of NaHCO₃ from, the basolateral bath resulted in a decrease of I_sc while G_tot remained unchanged. The Cl^--channel blocker DPC inhibited I_sc almost completely when added to the basolateral saline, whereas G_tot decreased moderately; however, V_sc depolarised without significant change of F_i. Ouabain had no influence on I_sc and G_tot. Increasing the basolateral [K⁺] resulted in a decrease in I_sc, while G_tot was not affected. At the same time V_sc largely depolarised and F_i decreased. Addition of the K⁺-channel blocker Ba⁺⁺ (5 mmol·1^-1) to the basolateral solution resulted in a two-step alteration of the transepithelial (I_sc, Gtot) and cellular (V_sc, F_i) parameters. The results are discussed with regard to (i) the mechanisms responsible for active transbranchial Cl^- uptake, and (ii) the technical improvement of being able to perform transport studies with crab gill preparations in an Ussing chamber.Abbreviations DMSO dimethylsulfoxide - DPC diphenylamine-2-carboxylate - F _{o, i} voltage divider ratio for external (o) and internal (i) barrier, respectively - G _Cl conductance related to the external [Cl^-] - G _tot total tissue conductance - I _Cl short-circuit current related to the external [Cl^-] - I _sc short-circuit current - PD _te transepithelial potential difference - R _ME resistance of the microelectrode - SITS 4-acetamido-4-isothiocyanato-stilbene-2,2-disulfonic acid - V _{o, i} open-circuit voltage across the external (o) and internal (i) barrier, respectively - V _sc intracellular potential under short-circuit conditions     

The semidwarf gene,sd-1, of rice (Oryza sativa L.). II. Molecular mapping and marker-assisted selection

To establish the location of the semidwarf gene, sd-1, the anthocyanin activator (A), purple node (Pn), purple auricle (Pau), and the isozyme locus, EstI-2, in relation to DNA markers on the molecular linkage map of rice, 20 RFLP markers, previously mapped to the central region of chromosome 1 (McCouch et al. 1988), were mapped onto an F₂ population derived from the cross Taichung 65 (A,Pn,Pau)/Taichung 65 (sd-1). sd-1 and EstI-2 were determined to be linked most tightly to RFLP markers RG 109 and RG 220, which cosegregated with each other. The distance between these RFLP markers and sd-1 was estimated to be 0.8 cM, based on an observed recombination value of 0.8%. The order of genes and markers in this region of chromosome 1 was determined to be sd-1 — (EstI-2 — RG220 — RG109) — RG381 — A — Pn — Pau. To test the efficacy of selection for sd-1 based on these linked markers, 50-day-old F₂ seedlings derived from another cross, Milyang 23/Gihobyeo, were analyzed for marker genotype. At this age, the semidwarf character could not be clearly detected based on phenotype. In addition, plant height was normally distributed in this population, making it difficult to unambiguously identify plants carrying sd-1. Thirteen seedlings homozygous for the sd-1-associated allele at EstI-2, RG220 and RG109, and 13 seedlings homozygous for the Sd-1-associated allele at all three marker loci were selected for further genetic analysis. At 20 days after heading, the culm lengths of these 26 plants were measured and the expected phenotype was confirmed in every case. These 26 plants were then selfed for four generations and F₆ lines were again evaluated to determine whether any recombination among the three molecular markers, or between these markers and the sd-1 gene, could be detected. No recombinants were identified, confirming the tight linkage of these loci and the usefulness of genotypic selection for this recessive semidwarf character prior to the time when it can be evaluated based on phenotype.     

An interstitial telomere array proximal to the distal telomere of mouse chromosome 13

Lambda clones of mouse DNA from BALB/c and C57BL/10, each containing an array of telomere hexamers, were localized by FISH to a region close to the telomere of Chr 13. Amplification of mouse genomic DNA with primers flanking SSRs within the cloned DNA showed several alleles, which were used to type eight sets of RI strains. The two lambda clones contained allelic versions of the interstitial telomere array, Tel-rs4, which is 495 bp in C57BL/10 and which includes a variety of sequence changes from the consensus telomere hexamer. Comparison of the segregation of the amplification products of the SSRs with the segregation of other loci in an interspecies backcross (C57BL/6JEi × SPRET/Ei) F₁× SPRET/Ei shows recombination suppression, possibly associated with ribosomal DNA sequences present on distal Chr 13 in Mus spretus, when compared with recombination in an interstrain backcross, (C57BL/6J × DBA/J) F₁× C57BL/6J, and with the MIT F₂ intercross. Analysis of recombination in females using a second interstrain backcross, (ICR/Ha × C57BL/6Ha) F₁× C57BL/6Ha, also indicates recombination suppression when compared with recombination in males of the same strains, using backcross C57BL/6Ha × (ICR/Ha × C57BL/6Ha) F₁. Thus, more than one cause may contribute to recombination suppression in this region. The combined order of the loci typed was D13Mit37–D13Mit30–D13Mit148–(D13Rp1, 2, 3, 4, Tel-rs4)–D13Mit53–D13Mit196–D13Mit77–(D13Mit78, 35). Data from crosses where apparently normal frequencies of recombination occur suggest that the telomere array is about 6 map units proximal to the most distal loci on Chr 13. This distance is consistent with evidence from markers identified in two YAC clones obtained from the region. Received: 24 September 1996/Accepted: 20 January 1997     

A fluorescent PCR assay for the codominant interpretation of a dominant SCAR marker linked to the virus resistance allele bc-1 2 in common bean

Our objective was to develop a rapid and accurate procedure to genotype common bean plants for the bc-1 ² allele, which conditions resistance to bean common mosaic and bean common mosaic necrosis viruses. A segregating F₂ population was derived from the cross between pinto bean breeding lines P94207-43 (bc-1 ²//bc-1 ²) and P94207-189 (bc-1//bc-1). A quantitative PCR assay based on the detection of fluorescent labeled amplicons was developed to distinguish between homozygous (bc-1 ²//bc-1 ²), heterozygous (bc-1 ²//bc-1) and null (bc-1//bc-1) F₂ genotypes. Remnant F₁ plants were used as a comparative reference sample. PCR results among this sample fit a normal distribution, and 99% and 95% confidence intervals for heterozygotes were determined. F₂ plants for which no amplification was detected were classified as null (bc-1//bc-1) genotypes. F₂ plants that fell within the confidence intervals for heterozygotes were classified as heterozygotes (bc-1 ²//bc-1), while plants that fell outside the right tail of the heterozygote confidence intervals were classified as homozygotes (bc-1 ²//bc-1 ²). F₂ plants were also genotyped for the bc-1 ² allele by performing F₃ family progeny tests for virus resistance. Agreement between the two methods for genotyping plants was 100% (59/59) when PCR genotyping was based on a 99% heterozygote confidence interval, and 98.3% (58/59) when based on a 95% heterozygote confidence interval. This assay will accelerate breeding for virus resistance in bean by facilitating discrimination among plants that are heterozygous or homozygous for the bc-1 ² allele. The experimental design may be generally applicable towards developing other assays for the codominant interpretation of dominant markers in diploid plants.     

The inheritance of a urease-null trait in soybeans

Summary Four soybean seed urease nulls (lacking both the activity and antigen of the embryo-specific urease) were intermated and the F₁ and F₂ seed examined for urease activity. Both generations were without urease activity, and the nulls were therefore considered noncomplementing. In crosses of each null line to cultivars homozygous for the allelic, codominantly inherited urease slow or fast isozyme, the F₁ seed expressed the embryo-specific urease isozyme of the urease-expressing parent. A 3 1 segregation for presence and absence of urease was observed in progeny from F₁ and heterozygous F₂ plants. The F₂ and F₃ from fastXnull combinations revealed that urease-positive seed were all phenotypically urease fast, while the same seed from slowXnull combinations showed a segregation of one seed containing a fast urease, either exclusively or in a heterozygous state with the slow isozyme, for every 69 phenotypic slows. Data pooled from F₂ plants which segregate for both the presence (Sun) and absence (Sun) of urease and for the fast (Eu1-b) or slow (Eu1-a) urease allele indicate that the null lesion (Sun) is linked to Eu1 by approximately one map unit. The evidence is consistent with two models: (1) sun is an allele at the embryo-specific urease isozyme locus (Eu1) and that a high degree of exchange (and/or conversion) within the locus results in a 1% recombination frequency between the null trait and urease allozyme; (2) sun is at a distinct locus which is separated by one map unit from the embryo-specific urease isozyme locus (Eu1) upon which it acts in the cis position. Polyadenylated embryo RNA from one of the null lines, PI 229324, exhibited no urease template activity in vitro. Thus, the lack of urease antigen is due to lack of accumulation of translatable urease mRNA. The availability of soybeans lacking seed urease should be extremely useful to breeders as a trait for linkage studies and to geneticists as a transformation marker.Portions of this work were funded by the Illinois and Missouri Agricultural Experiment Stations, the SOHIO-University of Illinois Center of Excellence in Crop Molecular Genetics and Genetic Engineering and by grants PCM-8219652 from the National Science Foundation and USDA/SEA-CRCR-1-1374 from the USDA Competitive Grants Office     

Effect of the mouse scid mutation on meiotic recombination

The goal of this study was to determine the effect of the mouse severe combined immunodeficiency (scid) mutation on the rate of meiotic recombination, by standard backcross linkage analysis. For this purpose, we examined four crosses that involved F₁ hybrid animals heterozygous for the strain C57BL/6 and BALB/c genomes. In one set of reciprocal crosses, F₁ animals were homozygous scid/scid, and in a second set of reciprocal crosses, F₁ mice were homozygous wild-type (+/+) at the scid locus. Backcross progeny were typed for recombination between selected genetic markers on mouse Chromosomes (Chrs) 1, 4, 6, 7, 9, 15, and 17. Although some differences in recombination were observed over some intervals, the expression of the SCID phenotype did not appear to have a major or consistent effect on meiotic recombination. Received: 4 October 1995 / Accepted: 2 April 1996     

Effects of selective destruction of iron-sulfur center B on electron transfer and charge recombination in Photosystem I

Incubation of spinach thylakoids with HgCl₂ selectively destroys Fe–S center B (F_B). The function of electron acceptors in F_B-less PS I particles was studied by following the decay kinetics of P700⁺ at room temperature after multiple flash excitation in the absence of a terminal electron acceptor. In untreated particles, the decay kinetics of the signal after the first and the second flashes were very similar (t _1/22.5 ms), and were principally determined by the concentration of the artificial electron donor added. The decay after the third flash was fast (t _1/20.25 ms). In F_B-less particles, although the decay after the first flash was slow, fast decay was observed already after the second flash. We conclude that in F_B-less particles, electron transfer can proceed normally at room temperature from F_X to F_A and that the charge recombination between P700⁺ and F_X ^-/A₁ ^- predominated after the second excitation. The rate of this recombination process is not significantly affected by the destruction of F_B. Even in the presence of 60% glycerol, F_B-less particles can transfer electrons to F_A at room temperature as efficiently as untreated particles.Abbreviations DCIP 2, 6-dichlorophenol indophenol - F_A, F_B, F_X iron-sulfur center A, B and X, respectively - PMS phenazine methosulfate     

Regulation of the activity of alcohol dehydrogenase isozymes during the development of the maize kernel

Summary The relative activities of alcohol dehydrogenase isozymes have been studied during the development of the endosperm and scutellum of heterozygous Adh ₁ ^F /Adh ₁ ^S maize kernels. The products of the Adh ₁ ^F allele are found earlier than the products of the Adh ₁ ^S allele in both the scutellum and the endosperm. A second gene (Adh _r )which controlsthe activity level of ADH is active in the scutellum only. The Adh _r ^N allele specifies increase in the relative activity of the Adh ₁ ^S products from 26 to 38 days after pollination. This increase is prevented by the Adh _r ^L allele which is dominant. These results ar discussed on the basis of the limited factor hypothesis proposed recently by Schwartz (1971) for the regulation of the Adh ₁gene in maize.     

Assessment of oxidative stress biomarkers – neuroprostanes and dihomo-isoprostanes – in the urine of elite triathletes after two weeks of moderate-altitude training

This randomized and controlled trial investigated whether the increase in elite training at different altitudes altered the oxidative stress biomarkers of the nervous system. This is the first study to investigate four F₄-neuroprostanes (F₄-NeuroPs) and four F₂-dihomo-isoprostanes (F₂-dihomo-IsoPs) quantified in 24-h urine. The quantification was carried out by ultra high pressure liquid chromatography-triple quadrupole-tandem mass spectrometry (UHPLC-QqQ-MS/MS). Sixteen elite triathletes agreed to participate in the project. They were randomized in two groups, a group submitted to altitude training (AT, n?=?8) and a group submitted to sea level training (SLT) (n?=?8), with a control group (Cg) of non-athletes (n?=?8). After the experimental period, the AT group triathletes gave significant data: 17-epi-17-F_2t-dihomo-IsoP (from 5.2?±?1.4?μg/mL 24?h^?1 to 6.6?±?0.6?μg/mL 24?h^?1), ent-7(RS)-7-F_2t-dihomo-IsoP (from 6.6?±?1.7?μg/mL 24?h^?1 to 8.6?±?0.9?μg/mL 24?h^?1), and ent-7-epi-7-F_2t-dihomo-IsoP (from 8.4?±?2.2?μg/mL 24?h^?1 to 11.3?±?1.8?μg/mL 24?h^?1) increased, while, of the neuronal degeneration-related compounds, only 10-epi-10-F_4t-NeuroP (8.4?±?1.7?μg/mL 24?h^?1) and 10-F_4t-NeuroP (5.2?±?2.9?μg/mL 24?h^?1) were detected in this group. For the Cg and SLT groups, no significant changes had occurred at the end of the two-week experimental period. Therefore, and as the main conclusion, the training at moderate altitude increased the F₄-NeuroPs- and F₂-dihomo-isoPs-related oxidative damage of the central nervous system compared to similar training at sea level.     

4-nor-β-Patchoulene sesquiterpenoids from the essential oil of Pogostemon cablin

Four nor-β-patchoulene sesquiterpenoids including three new compounds (1–3) and a new natural product (4) were isolated from the essential oil of the leaves and stems of Pogostemon cablin. Their structures were elucidated by detailed spectroscopic analysis, using 1D- and 2D-NMR techniques. This is the first report of 4-nor-β-patchoulenes from plants. All isolates were evaluated for the cytotoxic activities on human cancer cells in vitro. Compound 3 showed weak cytotoxic activities against NCI-H1975 and HePG-2 with IC₅₀ values of 49.9 μg/mL and 56.0 μg/mL, respectively.