Microsatellite–Centromere Mapping in Large Yellow Croaker (<Emphasis Type="Italic">Pseudosciaena crocea</Emphasis>) Using Gynogenetic Diploid Families

The large yellow croaker (Pseudosciaena crocea) is an economically important marine fish in China. Inheritance of 22 heterozygous microsatellite loci was examined in normal crossed diploid families and meio-gynogenetic families in P. crocea. Two gynogenetic families were produced via inhibition of the second polar body in eggs fertilized with UV-irradiated sperm. The ratio of gynogenesis was proven to be 100% and 96.9% in the two families, respectively. Of the 22 examined loci, 4 showed a segregation distortion in both control and gynogenetic families. Microsatellite–centromere (M–C) map distances were examined using 18 loci with normal Mendelian segregation. Estimated recombination rates ranged between 0 and 1.0 under the assumption of complete interference. High recombinant frequencies between heterozygous markers and the centromere were found in large yellow croaker, as in other teleosts. The average recombination frequency was 0.586. Ten loci showed high M–C recombination with frequency greater than 0.67. M–C distances provide useful information for gene mapping in large yellow croaker.     

The uaY positive control gene of Aspergillus nidulans: fine structure, isolation of constitutive mutants and reversion patterns

Summary The product of the uaY gene of Aspergillus nidulans is necessary for the expression of at least eight genes coding for enzymes and permeases of the purine utilisation pathway. A detailed fine structure map has been constructed of this gene involving 13 presumed point mutations and eight deletions. Gene conversion of these deletions was demonstrated. A technique was devised to select for constitutive mutations and two were obtained which map within the uaY gene. We have shown that the most centromere proximal allele reverts to a number of different phenotypes. The properties of this allele suggest that it may map in the open reading frame of the uaY gene, in a domain that could be altered in a way that would differentially affect the expression of genes under uaY control.     

Genetic linkage between C-bands and storage protein genes in chromosome 1B of tetraploid wheat

Summary Genetic mapping of polymorphic C-bands allows direct comparisons between genetic and physical maps. Eleven C-bands and two seed storage protein genes on chromosome 1B, polymorphic between Langdon durum and four accessions of T. dicoccoides, were used to study the distribution of recombination along the entire length of the chromosome. Recombination in the short arm was almost completely restricted to the satellite, two-thirds of the arm's length from the centromere; the Gli-B1 gene was found to be tightly linked to the telomeric C-band. In the long arm, the distal 51.4% of the arm accounted for 88% of recombination; the proximal half of the arm accounted for the remaining 12%. While the amount of crossing-over differed significantly between the four T. dicoccoides 1B chromosomes, there were no significant differences in the relative distributions of crossing-over along the chromosome. Consequently, the genetic maps obtained from the four individual T. dicoccoides chromosomes were combined to yield a consensus map of 14 markers (including the centromere) for the chromosome.     

Pre-zygotic embryological characters ofPlatycrater arguta, a rare and endangered species endemic to East Asia

Platycrater arguta Sieb. et Zucc. is a rare and endangered species endemic to East Asia. It produces two floral morphs viz. bisexual and male flowers. For bisexual flowers, simultaneous cytokinesis in the microsporocyte meiosis leads to a tetrahedral tetrad. The mature pollen grain is shed at 2-cell stage. The young anther wall is composed of epidermis, endothecium that develops fibrous thickenings at maturity, 1–2 middle layers and tapetum. The tapetum with uninucleate to binucleate cells, disintegrates in situ (glandular tapetum), yet in a small percentage of the anthers (about 37.6%), the tapetum does not disintegrate, causing complete male sterility. The ovules are anatropous, unitegmic, tenuinucellar and the formation of the embryo sac follows the monosporic, Polygonum type. Antipodal cells are lacking in the mature embryo sacs. Before fertilization, two polar nuclei fuse into a secondary nucleus. The formation of microsporangial wall, microsporogenesis and male gametogenesis in male flowers are analogous to those in the bisexual. Prezygotic embryological characters ofP. arguta were reported for the first time, revealing that its endangerment is correlated with the abortion of pollen of a part but not to the female development that is normal.     

Telomere-homologous sequences occur near the centromeres of many tomato chromosomes

Several bacteriophage lambda clones containinginterstitialtelomererepeats (ITR) were isolated from a library of tomato genomic DNA by plaque hybridization with the clonedArabidopsis thaliana telomere repeat. Restriction fragments lacking highly repetitive DNA were identified and used as probes to map 14 of the 20 lambda clones. All of these markers mapped near the centromere on eight of the twelve tomato chromosomes. The exact centromere location of chromosomes 7 and 9 has recently been determined, and all ITR clones that localize to these two chromosomes map to the marker clusters known to contain the centromere. High-resolution mapping of one of these markers showed cosegregation of the telomere repeat with the marker cluster closest to the centromere in over 9000 meiotic products. We propose that the map location of interstitial telomere clones may reflect specific sequence interchanges between telomeric and centromeric regions and may provide an expedient means of localizing centromere positions.     

Sequence and Chromosomal Localization of Mouse Annexin XI

Mouse annexin XI (anx11)²was cloned from a macrophage cDNA library and characterized by genetic linkage mapping, DNA sequencing, and structural comparison with other annexins. TheAnx11gene localized to mouse chromosome 14 in close linkage with theRarb, Plau,andWnt5agenes near the centromere and 1.8 cM distal from theAnx7gene. The open reading frame was flanked by long, untranslated regions and encoded a 503-amino-acid protein with 93.1% identity to its human orthologue. Its 189-aa amino terminus corresponded to the widely expressed variant 1 of two possible, alternatively spliced forms. A previously described peptide fromAplysia brasilianawas identified as a closely related invertebrate homologue. Since annexin XI is known to be localized in the nucleus at certain stages of development, the identification of a region in tetrad repeats 3 and 4 resembling the “chromo box” domain may be relevant to a nuclear regulatory function of annexin XI. Knowledge of the mouse cDNA sequence and genetic map location will assist in the analysis of genomic organization and expression and provide a useful animal model to investigate gene function and hereditary phenotype for annexin XI.     

Genome mapping of three major resistance genes to woolly apple aphid (Eriosoma lanigerum Hausm.)

Woolly apple aphid (WAA; Eriosoma lanigerum Hausm.) can be a major economic problem to apple growers in most parts of the world, and resistance breeding provides a sustainable means to control this pest. We report molecular markers for three genes conferring WAA resistance and placing them on two linkage groups (LG) on the genetic map of apple. The Er1 and Er2 genes derived from ‘Northern Spy’ and ‘Robusta 5,’ respectively, are the two major genes that breeders have used to date to improve the resistance of apple rootstocks to this pest. The gene Er3, from ‘Aotea 1’ (an accession classified as Malus sieboldii), is a new major gene for WAA resistance. Genetic markers linked to the Er1 and Er3 genes were identified by screening random amplification of polymorphic deoxyribonucleic acid (DNA; RAPD) markers across DNA bulks from resistant and susceptible plants from populations segregating for these genes. The closest RAPD markers were converted into sequence-characterized amplified region markers and the genome location of these two genes was assigned to LG 08 by aligning the maps around the genes with a reference map of ‘Discovery’ using microsatellite markers. The Er2 gene was located on LG 17 of ‘Robusta 5’ using a genetic map developed in a M.9 × ‘Robusta 5’ progeny. Markers for each of the genes were validated for their usefulness for marker-assisted selection in separate populations. The potential use of the genetic markers for these genes in the breeding of apple cultivars with durable resistance to WAA is discussed.     

The Yd2 gene for barley yellow dwarf virus resistance maps close to the centromere on the long arm of barley chromosome 3

Barley yellow dwarf luteovirus (BYDV) causes serious yield losses in all cereals worldwide. The Yd2 gene from a number of Ethiopian barleys (Hordeum vulgare L.) has been the most effective means of providing resistance against BYDV in cultivated barley. Isolation of the Yd2 gene will enable characterisation of the molecular basis of the Yd2-BYDV interaction. This paper describes the first stage in a project to isolate the gene: the construction of a detailed linkage map of the Yd2 region. The map encompasses 27.6 centiMorgans (cM) of chromosome 3 and contains 19 RFLPs, 2 morphological marker loci, the centromere and Yd2. In the mapping population of 106 F₂ individuals, Yd2 perfectly cosegregated with the RFLP loci Xwg889 and XYlp, which were located on the long arm, 0.5 cM from the centromere. The two morphological marker loci, uzu dwarfand white stripe j, both mapped distal to Yd2. The protein product of the gene at the XYlp locus will provide a convenient assay for the selection of Yd2 during the breeding of BYDV-resistant barley varieties.     

RFLP mapping of the centromere of chromosome 4 in maize using isochromosomes for 4S

 The centromere of maize chromosome 4 was previously localized to a 26-cM interval using molecular markers and B-A translocations. The objective of the present study was to refine the placement of the centromere using secondary trisomics. Two independently isolated secondary trisomics (having an isochromosome plus two normal homologs) for 4S were recovered. RFLP analysis of populations segregating for them placed the centromere of chromosome 4 between bnl15.45 and bnl7.20, two RFLP loci that are 5.4-cM apart on the UMC map and 11.5-cM apart on the BNL map. Received: 19 May 1997 / Accepted: 6 October 1997     

Proposed genetic nomenclature rules for Tetrahymena thermophila,Paramecium primaurelia and Paramecium tetraurelia. The Seventh International Meeting on Ciliate Molecular Biology Genetics Nomenclature.

Ordered tetrad data yield information on chromatid interference, chiasma interference, and centromere locations. In this article, we show that the assumption of no chromatid interference imposes certain constraints on multilocus ordered tetrad probabilities. Assuming no chromatid interference, these constraints can be used to order markers under general chiasma processes. We also derive multilocus tetrad probabilities under a class of chiasma interference models, the chi-square models. Finally, we compare centromere map functions under the chi-square models with map functions proposed in the literature. Results in this article can be applied to order genetic markers and map centromeres using multilocus ordered tetrad data.     

Assessment ofGibberella fujikuroi mating type by PCR

Mating type (MAT)-specific fragments of the two idiomorphs ofGibberella fujikuroi (anamorph,Fusarium moniliforme) were obtained by PCR amplification using primers to conserved regions ofMAT homologs from other fungal species and used to assign mating type by molecular criteria rather than the arbitrary historical designation. Mating type—strains of mating populations A-E and a mating type+strain of mating population F carry an α-box motif and should therefore be designatedMAT-1. Mating type+strains of mating populations A-E and a mating type—strain of mating population F carry an HMG-box motif and should be designatedMAT-2. Thus, assessment of mating type ofG. fujikurol strains can be easily achieved usingMAT-specific primers.     

Genetic linkage map of ISSR and RAPD markers in Einkorn wheat in relation to that of RFLP markers

 The potential of PCR-based markers for construction of a genetic linkage map in Einkorn wheat was investigated. From a comparison of polymorphisms between two Einkorn wheats, Triticum monococcum (Mn) and T. boeoticum (Bt), we obtained 49 polymorphic bands produced by 33 primers for inter-simple sequence repeat (ISSR) and 36 polymorphic bands shown by 25 combinations of random amplified polymorphic DNA (RAPD) primers for mapping in 66 individuals in the F₂ population. Although 44 ISSR fragments and 29 RAPD fragments statistically showed a 3 : 1 segregation ratio in the F₂ population, only 9 markers each of the ISSR and RAPD bands were able to be mapped on the RFLP linkage map of Einkorn wheat. ISSR markers were distributed throughout the chromosomes. The mapped positions of the ISSR markers seemed to be similar to those obtained by the RFLP markers. On the other hand, 4 of the 9 RAPD markers could map the RFLP marker-poor region on the short arm of 3A^m, suggesting a potential to map novel regions containing repetitive sequences. Comparisons of the genetic linkage map of Einkorn wheat to the linkage map and cytological map of common wheat revealed that the marker orders between the two maps of Einkorn wheat and common wheat coincided except for 4A, which harbors chromosome rearrangements specific for polyploid wheats, indicating a conservatism between the two genomes. Recombinations in Einkorn wheat chromosomes took place more frequently around the centromere and less at the distal part of chromosomes in comparison to those in common wheat. Nevertheless, recombinations even in Einkorn wheat chromosomes were strongly suppressed around the centromere. In fact, the markers located within 1 cM of the centromere were located almost in the central part of the chromosome arm. Received: 7 June 1997 / Accepted: 17 June 1997     

Influence of the sex of flowers on androgenesis in Aesculus hippocastanum L. anther culture

Summary Flowers of Aesculus hippocastanum L. are bisexual and zygomorphic, and are positioned on a 20–30 cm long inflorescence. Those located in the basal part of the panicle are female and fertile (segment A), flowers in the middle are bisexual (segment B), and those on top of the panicle are male (segment C). Androgenesis was achieved in anther culture which originated from three types of flowers cultured on modified Murashige and Skoog medium containing 2,4-dichlorophenoxyacetic acid (4.5 μM) and kinetin (4.6 μM). Differences in viability of uninuclear microspores were found between female (90.0%) and other flowers (bisexual 61.1%; male 72.7%.). Both the percentage of embryogenic anthers and the number of androgenic embryos formed per inflorescence differed according to the segment of origin. The highest embryogenic response was obtained in segment A (47.3%) and the lowest in segment C (24.1%). A significant difference was found between the number of androgenic embryos formed per inflorescence in segments A (921.0) and C (286.7). The highest germination percentage (21.3%) and plantelet formation (41.0%) were obtained on woody plant WPM liquid medium supplemented with 1% activated charcoal. Acclimation and regeneration were best from plantelets originating from female flowers (62.5%). Plantlets originating from bisexual and male flowers have much poorer survival (29.3 and 22.2%, respectively).     

Reduction in vacuolar volume in the tapetal cells coincides with conclusion of the tetrad stage in Arabidopsis thaliana

Although the tapetum is known for its role in the removal of the tetrad wall, a morphological change in the tapetum correlating with such a role has not been described. Here we report that in two ecotypes of Arabidopsis thaliana, Landsberg erecta and Columbia, the vacuoles in tapetal cells underwent progressive enlargement prior to the separation of tetrads but became drastically reduced when tetrads just separated from one another. Such a drastic change in vacuolar volume was not observed in later anther development. We also observed that the walls of associated tetrads were much less stained with Toluidine Blue O than the walls of separate tetrads, indicating that the tetrad walls underwent an alteration during the tetrad stage. Furthermore, we identified the N-terminal propeptide signals for sorting vacuolar proteins in 15 β-1,3-glucanases, five polygalacturonases, and two endocellulases that are expressed in Arabidopsis young floral buds; all three types of the enzymes are known to participate in degradation of the tetrad wall. These results suggest that the tapetal vacuoles might be a storage site for these enzymes prior to their secretion to the anther locule.     

Gene-centromere mapping of medaka sex chromosomes using triploid hybrids between Oryzias latipes and O. luzonensis

Four sex-linked genetic markers (SL1, SL2, B2.38 and stsOPQ05-1) on the sex chromosomes of the medaka, O. latipes, were mapped in relation to the centromere by means of triploid hybrids between O. latipes and O. luzonensis. Female F₁ hybrid O. latipes of two inbred strains, Hd-rR and HNI, were crossed with male O. luzonensis. Triploidization was induced by heat-shock treatment. Hatching rate of heat-shock treated eggs was 59%, and that of untreated hybrid eggs was 2%, indicating that most of the hatched fry were triploid. Using these triploid hatched fry, the map distances between the four loci and the centromere were examined. The order was SL2 – centromere – SL1 – B2.38 – stsOPQ05-1 and the map distances were: SL2 – centromere, 1%; centromere – SL1, 18%; SL1 – B2.38, 19%; B2.38 – stsOPQ05-1, 9%. Previous studies using FISH showed that SL2 is located on the short arm of large submetacentric chromosomes, and SL1 was closely linked to SDF (sex-determining factor). The results of gene-centromere mapping of this study show that SL1, B2.38 and stsOPQ05-1 are located on the long arm, and that, SDF is thus also on the long arm of the sex chromosomes.     

Microsatellite tagging of the stripe-rust resistance gene YrH52 derived from wild emmer wheat, Triticum dicoccoides, and suggestive negative crossover interference on chromosome 1B

 Stripe rust caused by Puccinia striifomis West. is one of the most devastating diseases relating to wheat production. Wild emmer wheat, Triticum dicoccoides, the tetraploid progenitor of cultivated wheat, has proven to be a valuable source of novel stripe-rust resistance genes for wheat breeding. For example, T. dicoccoides accessions from Mt. Hermon, Israel, are uniformly and highly resistant to stripe-rust. The main objective of the present study is to map a stripe-rust resistance gene, derived from the unique Mt. Hermon population of wild emmer, using microsatellite markers. An F₂ mapping population was established by crossing stripe-rust resistant T. dicoccoides accession H52 from Mt. Hermon with the Triticum durum cultivar Langdon. The stripe-rust resistance derived from accession H52 was found to be controlled by a single dominant gene which was temporarily designated as YrH52. Out of 120 microsatellite markers tested, 109 (91%) showed polymorphism between the parental lines. Among 79 segregating microsatellite loci generated from 56 microsatellite primer pairs, nine were linked to YrH52 with recombination frequencies of 0.02–0.35, and LOD scores of 3.56–54.22. A genetic map of chromosome 1B, consisting of ten microsatellite loci and the stripe-rust resistance gene YrH52, was constructed with a total map length of 101.5 cM. YrH52 is also closely linked to RFLP marker Nor1 with a map distance of 1.4 cM and a LOD value of 29.62. Apparent negative crossover interference was observed in chromosome 1B, especially in the region spanning the centromere. Negative crossover interference may be a common characteristic of gene-rich regions or gene clusters in specific chromosomes. Received: 30 October 1998 / Accepted: 2 November 1998     

Inter-populational difference in microsatellite–centromere map distances in the loach, <Emphasis Type="Italic">Misgurnus anguillicaudatus</Emphasis>

Microsatellite–centromere recombination rates were estimated at 21 loci in relation to centromere of chromosomes in gynogenetic diploid lines induced from loaches Misgurnus anguillicaudatus of two different populations in Japan. All the microsatellite loci gave allelic segregation according to the Mendelian manner of inheritance in normal diploid families. Since loaches from the Kita population in the southern area of Hokkaido Island and those from the Memanbetsu population in the northern area, Hokkaido, Japan, were reported by previous genetic studies to be genetically diversified, map distances were compared between loaches from the two different populations. Three (Mado7, Mac3 and Mac49) of five loci, which could be compared inter-populationally, gave significantly different recombination rates, i.e., map distances. The results support the presence of genetic difference between the two populations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Application of Arabidopsis AGAMOUS second intron for the engineered ablation of flower development in transgenic tobacco

To explore a new approach to generating reproductive sterility in transgenic plants, the barnase gene from Bacillus amyloliquefaciens was placed under the control of an 1853-bp nucleotide sequence from the 3′end of the second intron of Arabidopsis AGAMOUS and CaMV 35S (−60) minimal promoter [AG-I-35S (−60)::Barnase], and was introduced into tobacco through transformation mediated by Agrobacterium tumefaciens. All AG-I-35S (−60)::Barnase transgenic plants showed normal vegetative growth and 28% of the transgenic lines displayed complete ablation of flowering. Two transgenic lines, Bar-5 and Bar-15, were 98.1 and 98.4% sterile, respectively, as determined by seed production and germination. When controlled by AG-I-35S (−60) chimeric promoter, barnase mRNA was detected in the reproductive tissues of transgenic tobacco plants, but not in vegetative parts. This study presents the first application of an AG intron sequence in the engineered ablation of sexual reproduction in plants. The AG-I-35S (−60)::Barnase construct can be useful in diminishing pollen and seed formation in plants, providing a novel bisexual sterility strategy for interception of transgene escape and has other potentially commercial use for transgenic engineering.     

Rat Chromosome 1: Regional localization of seven genes (Slc9a3, Srd5a1, Esr, Tcp1, Grik5, Tnnt3, Jak2) and anchoring of the genetic linkage map to the cytogenetic map

Seven genes were regionally localized on rat Chromosome (Chr) 1, from 1p11 to 1q42, and two of these genes were also included in a linkage map. This mapping work integrates the genetic linkage map and the cytogenetic map, and allows us to orient the linkage map with respect to the centromere, and to deduce the approximate position of the centromere in the linkage map. These mapping data also indicate that the Slc9a3 gene, encoding the Na⁺/H⁺ exchanger 3, is an unlikely candidate for the blood pressure loci assigned to rat Chr 1. These new localizations expand comparative mapping between rat Chr 1 and mouse or human chromosomes. Received: 21 March 1997 / Accepted: 3 May 1997