bluuebunny/crossref_metadata_2025 huggingface dataset:
B–A chromosome mediated 3:1 disjunction in heterozygous reciprocal translocations of maize
Authors: Kindiger B. , Hamann S.
Published: April 2011

In maize (Zea mays L.), meiotic segregation products of reciprocal translocations are well defined. The predictible meiotic behaviors and products generated by these interchanges allow them to be used as tools to gain basic information in cytogenetics, genetics, and plant breeding. In combining a classic reciprocal translocation with a single B–A chromosome from a tertiary trisomic B–A translocation stock, unique individuals with unusual chromosome karyotypes are generated. In cases where a B–A chromosome was present, the frequency of 3:1 disjunction within the ring of four was increased. In the case of T6–9(5454) + B–6Ld, cytological identification, via root-tip mitosis, was able to identify the specific tertiary trisomic products generated. These karyotypes are predictable and highly repeatable. Such karyotypes may have specific uses in chromosome mapping, chromosome dosage studies, or genetic or molecular investigations.Key words: reciprocal translocations, tertiary trisomes, interchange trisomes, B–A translocations, maize.
Restriction fragment length polymorphism and genetic distance among Mexican accessions of Capsicum
Authors: Prince James P. , Loaiza-Figueroa Fernando , Tanksley Steven D.
Published: April 2011

Restriction fragment length polymorphism analysis was performed on 25 accessions of pepper (Capsicum sp.) from various regions of Mexico and on the two parents currently in use for molecular mapping. The fragments detected were used to estimate genetic distances among the accessions. A dendrogram from cluster analysis and a principal component analysis diagram of the genetic distance matrix are presented. The correlation between genetic distances measured by restriction fragment length polymorphism versus genetic distances measured by isozymes is good (R2 = 0.438, p = 0.0001). All but four accessions could be differentiated with the 10 most polymorphic clones examined. Crosses were made between each of our two mapping parents and the Mexican accessions as well as among many of the Mexican accessions. F1 pollen stainability data were taken to estimate the fertility of each cross. This information along with the genetic distance data is used to select polymorphic but interfertile parents for future restriction fragment length polymorphism mapping in pepper.Key words: pepper, cluster analysis, isozyme-RFLP correlation, DNA fingerprinting.
The evolutionary history of Drosophila buzzatii. XXIII. High content of nonsatellite repetitive DNA in D. buzzatii and in its sibling D. koepferae
Authors: Marin I. , Labrador M. , Fontdevila A.
Published: April 2011

The frequency and types of repetitive nonsatellite DNA of two sibling species of the repleta group of Drosophila, D. buzzatii, and D. koepferae have been determined. For each species, the analysis is based on a sample of more than 100 clones (400 kb) obtained from genomic DNA. A theoretical model has been developed to correct for the presence of a mixture of repetitive and unique DNA in these clones. After correction, a high content of repetitive DNA has been demonstrated for both species (D. buzzatii, 19–26%; D. koepferae, 27–32%). The repetitive sequences have been classified according to their hybridization pattern when used as probes against genomic DNA and by their in situ hybridization signals on polytene chromosomes. Data suggest that the main nonsatellite component of these species is simpler and more repetitive than that of D. melanogaster, pointing to a wide variability in content and class size distribution of repetitive DNA among Drosophila species.Key words: repetitive DNA, DNA evolution, Drosophila, repleta group, sibling species.
Differential transmission of homoeologous chromosomes in heterozygous amphiploids: rRNA loci of Thinopyrum distichum in an amphiploid with Triticum durum
Authors: Armstrong K. C. , Molnar S. J. , Fedak G.
Published: April 2011

The segregation of two sets of homoeologous Thinopyrum chromosomes from Th. distichum (5J and 6J) was followed in segregating BC1F2 progeny from the backcross (2n = 42) of the amphiploid of Triticum durum × Th. distichum) (2n = 56) to T. durum (2n = 28). The segregation pattern was followed by the presence or absence of the 18S + 26S rRNA locus using in situ hybridization and Southern analysis of the TaqI digest. The BC1F2 progeny segregated for four to seven NOR chromosomes. This confirmed that one homoeologue carried a nucleolar organizing region (NOR), while in the other it was absent or greatly reduced in copy number. That is, for example, 5J1 and 6J1 carry a NOR site, while 5J2 and 6J2 both lack NORs. Both in situ hybridization and Southern analysis confirmed that presence or absence of NORs did not segregate at random. The NOR on 5J had a 2.9-kb TaqI fragment and this NOR was present in the progeny less frequently than expected. The 6J NOR that carried a 1.1- and 0.8-kb fragment was transmitted to the progeny with a normal frequency. The results are discussed with respect to the implications for creating reconstructed genomes and recovering the genetic variation of a polyploid in addition lines.Key words: segregation, homoeologue, rRNA, amphiploid, polyploid, reconstructed genome, in situ hybridization, TaqI fragment.
Polyphyletic origins of Brassica napus: new evidence based on organelle and nuclear RFLP analyses
Authors: Song Keming , Osborn Thomas C.
Published: April 2011

Accessions representing a range of diversity in Brassica napus and their potential diploid progenitor species were analyzed using nuclear, chloroplast (ct), and mitochondrial (mt) RFLPs. Based on RFLPs of ctDNA and mtDNA, cytoplasmic genomes of the diploid species examined could be classified into four major types, represented by almost all B. rapa, Broccoletto (a specialized form of B. rapa), B. oleracea, and B. montana. Results from phylogenetic analyses of these data suggest that B. montana might be closely related to the prototype that gave rise to both cytoplasms of B. rapa and B. oleracea. The four major types of cytoplasms found in the diploid species were also observed in B. napus accessions. A majority of the cultivated B. napus examined contained a cytoplasm different from those of either B. rapa and B. oleracea. These B. napus accessions (designated M/N cytoplasm type) had the same chloroplast genome as that of B. montana and a unique mitochondrial genome that was somewhat intermediate between those of B. montana and B. rapa. These results strongly support the concept of multiple origins of B. napus and provide the first evidence that most cultivated forms of B. napus were derived from a cross in which a closely related ancestral species of B. rapa and B. oleracea was the maternal donor. Phylogenetic relationships based on nuclear RFLPs clearly separated B. napus accessions having different cytoplasm types, providing further evidence for multiple origins of B. napus. Brassica napus accessions having M/N type cytoplasm were clustered together as three subgroups: one contained oilseed cultivars from Canada, a second contained oilseed cultivars from Europe, and a third contained accessions of rutabaga.Key words: Brassica napus, molecular taxonomy, RFLP, chloroplast, mitochondrion.
Cytology and reproductive behavior of hybrids between Paspalum urvillei and two hexaploid P. dilatatum biotypes
Authors: Burson Byron L.
Published: April 2011

Sexual, tetraploid (2n = 4x = 40) vaseygrass (Paspalum urvillei Steud.) was crossed with two apomictic, hexaploid (2n = 6x = 60) dallisgrass (P. dilatatum Poir.) biotypes (Uruguayan and Uruguaiana) to determine their relationships and the reproductive behavior of the hybrids. One vaseygrass × Uruguayan and two vaseygrass × Uruguaiana hybrids were studied and all had 2n = 5x = 50 chromosomes. The mean pairing meiotic association for the vaseygrass × Uruguayan hybrid was 10.18 I and 19.91 II, and for the two vaseygrass × Uruguaiana hybrids was 10.28 I, 19.82 II, 0.006 III, and 0.01 IV. These findings indicate that the parents of both hybrids have two homologous genomes. Because vaseygrass and Uruguayan dallisgrass have the genome formulas IIJJ and IIJJXX, respectively, their hybrid has the formula IIJJX and the two homologous genomes are the I and J genomes. Likewise, chromosome pairing in the vaseygrass × Uruguaiana hybrids demonstrates that both species have two similar genomes, I and J. The Uruguaiana biotype usually has 8–10 univalents per cell and these result from the failure of some members of the third genome to pair. Thus the Uruguaiana biotype has different forms of the X genome, and its genome formula may be designated as IIJJXX2. Cytologically all three hybrids were facultative apomicts but their uniform F2 progeny indicates that only the apomictic embryo sacs are functional. Seed fertility ranged from 10.8 to 16.2%.Key words: Interspecific hybrids, genomes, chromosome pairing, species relationships, dallisgrass, vaseygrass.
Physical mapping of the 18S–5.8S–26S rRNA genes in barley by in situ hybridization
Authors: Leitch I. J. , Heslop-Harrison J. S.
Published: April 2011

The 18S–5.8S–26S rRNA genes have been located on five pairs of barley (Hordeum vulgare L., 2n = 2x = 14) chromosomes (in descending order of copy number, barley chromosome numbers 6, 7, 5, 1, and 2; homoeologous groups 6I, 5I, 1I, 7I, and 2I) by in situ hybridization followed by C-banding. All sites were at intercalary positions. The pairs of major sites on chromosomes 6 (6I)1 and 7 (5I) are well known. Silver staining of nuclei and meiotic analysis have previously indicated that additional rDNA sites may be present, but the presence of sites on a further three chromosome pairs was unexpected. Within the tribe Triticeae, few species have more than two pairs of rDNA sites, and they have not been reported on group 2 chromosomes. We propose calling the new sites Nor-I1 (on chromosome 5 (1I)), Nor-I4 (on chromosome 1 (7I)), and Nor-I5 (on chromosome 2 (2I)), and that any further rDNA sites on homoeologous group 2 chromosomes should be called Nor-5. As conventional, all designations are based on temporal order of discovery in the Triticeae and designating the H. vulgare genome as I. In situ hybridization is valuable for gene mapping, since it can detect the presence of genes with a very wide range of copy numbers at different sites.Key words: C-banding, nucleolus organizer regions, fluorescent in situ hybridization, Hordeum vulgare, gene mapping.
Variation in nuclear DNA amount between wild and cultivated populations of Milium effusum (2n = 28)
Authors: Bennett Simon T. , Bennett Michael D.
Published: April 2011

Mean 2C DNA amounts varied by 35.6%, ranging from 7.52 to 10.20 pg, between 10 populations of the grass Milium effusum L. Such intraspecific variation occurred despite a constant chromosome number (2n = 28) and no obvious differences in karyotype. Plants originating from botanic garden populations growing in cultivation had significantly (P < 0.001) larger DNA amounts than plants collected from wild populations. Moreover, variation in DNA amount within either the "cultivated" or the "wild" groups was not significant. As the environment in which plants are kept in botanic gardens is clearly different to the natural habitat for M. effusum, it seems likely that the difference in nuclear DNA amount is causally related, perhaps through its nucleotypic effects, to microclimate adaptation. These results suggest that at least some genotypes of M. effusum are fluid and sensitive to environmental change. Such data may have broad practical importance regarding plant responses to various environmental changes such as a nuclear winter and global warming, and implications for plant conservation and reintroduction. Milium effusum is a potentially useful plant material for studying the nature of intraspecific variation in DNA amount.Key words: Milium effusum, nuclear DNA amounts, nucleotype, environmental adaptation.
Image analysis of C-banded chromosomes and pairing regionalization in wheat
Authors: Bernardo Angeles , Montero Martin , Cuadrado Angeles , Jouve Nicolás
Published: April 2011

C-banding and image analysis are used to characterize nine somatic chromosomes of wheat and to quantify a series of physical parameters (arm length, heterochromatic band intensity and position) in tetraploid Triticum turgidum and hexaploid T. aestivum wheat. The arm-by-arm meiotic association of the chromosomes at first meiotic metaphase is evaluated with respect to these parameters and genetic pairing regulators. The effect of the genetic factors is analyzed comparatively in homozygous lines or both normal and mutant lines (Ph1/Ph1, ph1a/ph1a, ph1b/ph1b, and ph1c/ph1c) and in aneuploids (ditelo-5BL and nulli-5B–tetra-5D). The pairing values were progressively reduced as follows: 'Chinese Spring' Ph1/Ph1 > 'Chinese Spring' dt-5BL > 'Chinese Spring' ph1a/ph1a > 'Chinese Spring' nulli-5B–tetra-5D > 'Chinese Spring' ph1b/ph1b > 'Cappelli' ph1c/ph1c. The results indicate that although a different contribution to overall pairing exists for each specific chromosome region, the differences in the genetic systems regulating pairing from line to line indiscriminately affected chiasma levels and did not lead to specific deviations in any line. The results seem to show that maintenance of chiasmata at first metaphase of meiosis depends on chromosome length and correlation is strong for the chance of double chiasmata. Moreover, there are indications that some C-bands, particularly in intercalary positions in chromosome arms 4AL, 2BL, 5BS, and 7BL, increase the frequency of chiasma at first metaphase. The pairing intensity in each specific chromosomal segment may be the product of an integrated action of chromosome length, the presence or absence of heterochromatin, and genetic factors.Key words: image analysis, heterochromatin, Triticum, C-banding, meiotic pairing.
C-heterochromatin polymorphism in holocentric chromosomes of Triatoma infestans (Hemiptera: Reduviidae)
Authors: Panzera Fco , Alvarez F. , Sanchez-Rufas J. , Pérez R. , Suja J. A. , Scvortzoff E. , Dujardin J. P. , Estramil E. , Salvatella R.
Published: April 2011

This is the first report of intraspecific variation of C-bands in Heteroptera, described in natural populations of Triatoma infestans (Hemiptera: Reduviidae), the main vector of Chagas disease in Uruguay. Marked variation in number, position, and size of C-heterochromatic bands was found in the three large autosomal pairs. A geographical pattern of this chromosomal polymorphism was observed. Evolutionary importance and epidemiological relevance are discussed.Key words: Triatoma infestans, cytogenetics, C-band polymorphism, holocentric chromosomes, Chagas disease.
Restriction fragment length polymorphisms of a chloroplast photosystem II gene from poplar and their use for species identification
Authors: Vornam Barbara , Herzog Sven , Preisig-Müller Regina , Hattemer Hans H.
Published: April 2011

In a total DNA library from the poplar clone Beaupré (Populus trichocarpa × P. deltoides) one DNA clone was found to identify restriction site polymorphisms in different poplar species. This clone represents a cpDNA gene that shows close homology to a photosystem II gene of pea and spinach coding for the D2 protein and the 44 kDa reaction centre. In Southern blot analysis this probe identified interspecific restriction site variation among the different poplar species; intraspecific variation was not detectable. As the chloroplast genome is maternally inherited in poplars this cpDNA probe was used for identification of P. nigra or P. deltoides as the seed parents of F1 hybrid trees in natural stands of western Germany.Key words: Populus, restriction fragment length polymorphism, chloroplast, photosystem II, species identification.
Synaptonemal complex analysis of domestic sheep (Ovis aries) with Robertsonian translocations. III. Deficient pairing and NOR role in Massey III heterozygotes
Authors: Dai K. , Gillies C. B. , Dollin A. E.
Published: April 2011

Spermatocytes from rams heterozygous for Massey translocation III (t37;25) contained one trivalent and those from the rams heterozygous for both Massey translocations I and III (t1t3) contained two trivalents. Where two trivalents and the XY pair are present in the same nucleus they may form a synaptonemal complex (SC), but no SC segment is found between the two trivalents. The frequency of pairing abnormality in four t3 rams and two t1t3 rams did not significantly differ from that in the normal sheep, but t3 trivalents with diverse abnormal configurations were recorded. A hypothesis was proposed that nucleolar organizer regions (NORs) or nucleoli could account for deficient pairing behaviour and hence chromosome rearrangement, because the NOR region on an NOR-bearing chromosome was usually delayed in pairing, and unpaired regions tended to associate with other unpaired axes or SCs.Key words: Bovidae, NOR, deficient pairing, chromosome rearrangement.
Female meiosis in the onion fly and cabbage root fly (Diptera: Anthomyiidae)
Authors: Hartman T. P. V. , Southern D. I.
Published: April 2011

The sequence of female meiosis was investigated in two populations of the cabbage root fly (Delia radicum) and three populations of the onion fly (D. antiqua). In contrast with the completely achiasmate males, both species showed high levels of recombination in females. However, significant differences in chiasma frequency occurred between individuals within populations and between the populations. It was not uncommon to find aneuploidy of the X chromosomes. The autosomes occasionally showed asynapsis or desynapsis, but normal disjunction of univalents was facilitated by distance pairing.Key words: meiosis, female, chiasmata, diptera, achiasmate, oogenesis.
Molecular-genetic maps for group 1 chromosomes of Triticeae species and their relation to chromosomes in rice and oat
Authors: Deynze A. E. Van , Dubcovsky J. , Gill K. S. , Nelson J. C. , Sorrells M. E. , Dvořák J. , Gill B. S. , Lagudah E. S. , McCouch S R , Appels R.
Published: April 2011

Group 1 chromosomes of the Triticeae tribe have been studied extensively because many important genes have been assigned to them. In this paper, chromosome 1 linkage maps of Triticum aestivum, T. tauschii, and T. monococcum are compared with existing barley and rye maps to develop a consensus map for Triticeae species and thus facilitate the mapping of agronomic genes in this tribe. The consensus map that was developed consists of 14 agronomically important genes, 17 DNA markers that were derived from known-function clones, and 76 DNA markers derived from anonymous clones. There are 12 inconsistencies in the order of markers among seven wheat, four barley, and two rye maps. A comparison of the Triticeae group 1 chromosome consensus map with linkage maps of homoeologous chromosomes in rice indicates that the linkage maps for the long arm and the proximal portion of the short arm of group 1 chromosomes are conserved among these species. Similarly, gene order is conserved between Triticeae chromosome 1 and its homoeologous chromosome in oat. The location of the centromere in rice and oat chromosomes is estimated from its position in homoeologous group 1 chromosomes of Triticeae.Key words: Triticeae, RFLP, consensus, comparative.
Physical mapping of 5S and 18S–25S rDNA and repetitive DNA sequences in Aegilops umbellulata
Authors: Castilho A. , Heslop-Harrison J. S.
Published: April 2011

An accurate physical map of the location of the 5S and the 18S–5.8S–25S rRNA genes and a repetitive DNA sequence has been produced on Aegilops umbellulata Zhuk., (2n = 2x = 14) chromosomes by in situ hybridization. Chromosome morphology together with the hybridization pattern of pSc119.2, a DNA sequence from rye, allowed identification and discrimination of different chromosomes; pSc119.2 hybridizes with all Ae. umbellulata chromosomes at the telomeres, except for the short arm of chromosome 6U, and shows intercalary sites on the long arms of chromosomes 6U and 7U. The 5S and 18S–25S rDNA have been mapped physically only on the short arms of chromosomes 1U and 5U. On chromosome 1U the order of the genes is 5S rDNA subterminal and 18S–25S rDNA more proximal, while on chromosome 5U the position of the genes is reversed. The relative order of the genes, together with the hybridization pattern of the pSc119.2, is useful in identifying whole chromosomes or chromosome segments from Ae. umbellulata in recombinant or addition lines with wheat. The data help link the physical organization of chromosomes to the genetic map. Other members of the Triticeae vary in the presence and order of the 5S and 18S–25S rDNA sequences on groups 1 and 5, indicating multiple and complex evolutionary rearrangements of the chromosome arms.Key words: Triticum umbellulatum.
Nucleotide sequence and genomic organization of cichlid fish minisatellites
Authors: Harris Andrew S. , Wright Jonathan M.
Published: April 2011

We have cloned, sequenced, and determined the genomic organization of minisatellites from the African cichlid fish, Oroechromis niloticus. We estimate that minisatellites related in sequence to the Jeffreys' core probes 33.6 and 33.15 occur approximately every 1000 kilobase pairs in the cichlid fish genome. Sequencing of three minisatellites revealed that the size of the monomer units of the tandem arrays ranged from 7 to 24 base pairs (bp). One minisatellite appeared to contain a higher ordered periodicity of 90–120 bp superimposed on the apparent 15 bp monomer repeat, indicating a particularly large unit of homogenization for a minisatellite array. Sequence heterogeneity of repeat units within tandem arrays varied considerably from one minisatellite to another. Hybridization of cloned minisatellites to genomic DNA of cichlid fishes generated, in most instances, multilocus fingerprint patterns, indicating that families of minisatellites related by sequence exist in the cichlid genome. Two minisatellite clones, however, generated polymorphic single locus fingerprints, suggesting that these loci are conserved in closely related African cichlids. The cross hybridization of these cichlid minisatellites within and between related taxa, as well as to unrelated fish species such as Atlantic salmon (Salmo salar), complement the human minisatellite sequences for the study of genetic relationships among individuals from a wide range of fish species.Key words: variable number of tandem repeats, VNTR, tilapia, evolution, DNA fingerprinting.
Microsatellite fingerprinting in the genusPhaseolus
Authors: Hamann Andrea , Zink Dorothea , Nagl Walter
Published: April 2011

The genetic variability of the genus Phaseolus was investigated by nonradioactive DNA fingerprinting. The simple repetitive sequences (GATA)4, (GACA)4, (CAC)5, and (CA)8were used as probes to differentiate 18 species comprised of 90 genotypes. (GATA)4, (CAC)5, and (CA)8could be detected in the genome of nearly all species, while the (GACA)4motif occurred only in 13 species. Almost all fragments that hybridized with (GACA)4also hybridized with (GATA)4. All but two cultivars of Phaseolus vulgaris, P. lunatus, P. acutifolius, and P. polyanthus showed specific banding patterns with (GATA)4. The other repetitive motifs revealed only limited or no intraspecific variation. In P. vulgaris, two group-specific patterns were found with (GATA)4, giving further evidence for a Middle American and an Andean origin of the P. vulgaris genotypes. The high intraspecific pattern variation that was revealed with (GATA)4in the predominantly self-pollinating species P. vulgaris and P. lunatus can probably be explained by there being at least two primary centres of domestication and, hence, genetic diversification. In cross-pollinating species (e.g., P. coccineus), the observed intraspecific variation was, surprisingly, rather low. The present study shows that DNA fingerprinting with microsatellites successfully distinguishes among gene pools, cultivars, and, in some cases, among individuals.Key words: Leguminosae, plants, nonradioactive, simple sequences, digoxigenated oligonucleotide probes.
Molecular mapping of wheat. Homoeologous group 2
Authors: Nelson James C. , Deynze Allen E. Van , Sorrells Mark E. , Autrique Enrique , Lu Yun Hai , Merlino Marielle , Atkinson Mark , Leroy Philippe
Published: April 2011

A molecular-marker map of bread wheat having many markers in common with other grasses in the Gramineae family is a prerequisite for molecular level genetic studies and breeding in this crop species. We have constructed restriction fragment length polymorphism maps of the A-, B-, and D-genome chromosomes of homoeologous group 2 of hexaploid wheat (Triticum aestivum L. em. Thell) using 114 F7lines from a synthetic × bread wheat cross and clones from 11 libraries. Chromosomes 2A, 2B, and 2D comprise 57, 60, and 56 markers and each spans about 200 cM. Comparisons between chromosomes are facilitated by 26 sets of homoeoloci. Genes mapped include a heterologous abscisic acid responsive locus cloned as pBS128, the epidermal waxiness inhibitor W21, and two presumed leaf rust and stem rust resistance genes. Anomalies suggesting ancestral rearrangements in chromosome 2B are pointed out and features of wheat group 2 chromosomes that are common to barley (Hordeum vulgare L.), rice (Oryza spp.), and T. tauschii are discussed.Key words: RFLP, wheat, waxy, rust.
RFLP mapping of five major genes and eight quantitative trait loci controlling flowering time in a winter × spring barley (Hordeum vulgareL.) cross
Authors: Laurie D. A. , Pratchett N. , Snape J. W. , Bezant J. H.
Published: April 2011

A genetic map of 92 RFLP loci and two storage protein loci was made using 94 doubled-haploid lines from a cross between the winter barley variety Igri and the spring variety Triumph. The markers were combined with data from two field experiments (one spring sown and one autumn (fall) sown) and a glasshouse experiment to locate a total of 13 genes (five major genes and eight quantitative trait loci (QTL)) controlling flowering time. Two photoperiod response genes were found; Ppd-H1 on chromosome 2(2H)S regulated flowering time under long days, while Ppd-H2 on chromosome 5(1H)L was detected only under short days. In the field experiments Ppd-H1 strongly affected flowering time from spring and autumn sowings, while Ppd-H2 was detected only in the autumn sowing. The glasshouse experiment also located two vernalization response genes, probably Sh and Sh2, on chromosomes 4(4H)L and 7(5H)L, respectively. The vernalization response genes had little effect on flowering time in the field. Variation in flowering time was also affected by nine additional genes, whose effects were not specifically dependent on photoperiod or vernalization. One was the denso dwarfing gene on chromosome 3(3H)L. The remaining eight were QTLs of smaller effect. One was located on chromosome 2(2H), one on 3(3H), one on 4(4H), one on 7(5H), two on 6(6H), and two on 1(7H). Model fitting showed that the 13 putative genes, and their interactions, could account for all the observed genetical variation from both spring and autumn sowings, giving a complete model for the control of flowering time in this cross.Key words: barley, Hordeum vulgare, flowering time, photoperiod, vernalization, mapping.
Cytogenetic analysis of Malpighian tubule and salivary gland polytene chromosomes of Bactrocera oleae (Dacus oleae) (Diptera: Tephritidae)
Authors: Zambetaki Anna , Kleanthous Kleanthis , Mavragani-Tsipidou Penelope
Published: April 2011

Photomaps of the Malpighian tubule and the salivary gland polytene chromosomes of Bactrocera oleae (Dacus oleae) are presented and compared with those of the fat body. Five polytene chromosomes (10 polytene arms) corresponding to the five autosomes of the mitotic nuclei, as well as a heterochromatic mass corresponding to the sex chromosomes, are observed in the nuclei of the three somatic tissues. The most prominent features of each polytene chromosome, the reverse tandem duplications, as well as the rather unusual ectopic pairing of the telomeric regions of different chromosome arms, are described. The constancy of the banding pattern based on the analysis of the three larval tissues is discussed.Key words: Bactrocera oleae (Dacus oleae), polytene chromosomes, salivary gland, Malpighian tubule, banding pattern.
Identification of the A and C genomes of amphidiploidBrassica napus(oilseed rape)
Authors: Parkin I. A. P. , Sharpe A. G. , Keith D. J. , Lydiate D. J.
Published: April 2011

A genetic linkage map consisting of 399 RFLP-defined loci was generated from a cross between resynthesized Brassica napus (an interspecific B. rapa × B. oleracea hybrid) and "natural" oilseed rape. The majority of loci exhibited disomic inheritance of parental alleles demonstrating that B. rapa chromosomes were each pairing exclusively with recognisable A-genome homologues in B. napus and that B. oleracea chromosomes were pairing similarly with C-genome homologues. This behaviour identified the 10 A genome and 9 C genome linkage groups of B. napus and demonstrated that the nuclear genomes of B. napus, B. rapa, and B. oleracea have remained essentially unaltered since the formation of the amphidiploid species, B. napus. A range of unusual marker patterns, which could be explained by aneuploidy and nonreciprocal translocations, were observed in the mapping population. These chromosome abnormalities were probably caused by associations between homoeologous chromosomes at meiosis in the resynthesized parent and the F1plant leading to nondisjunction and homoeologous recombination.Key words: genetic linkage map, homoeologous recombination, Brassica rapa, Brassica oleracea, genome organization.
Genomic organization of 57 ribosomal protein genes in rice (Oryza sativaL.) through RFLP mapping
Authors: Wu Jianzhong , Matsui Eriko , Yamamoto Kimiko , Nagamura Yoshiaki , Kurata Nori , Takuji Sasaki , Minobe Yuzo
Published: April 2011

Four hundred cDNA clones from rice (Oryza sativa L.) callus and root cDNA libraries, with a high similarity to about 70 kinds of ribosomal proteins (r-protein) in eukaryotic as well as prokaryotic organisms, were identified by their deduced amino acid sequences. Southern hybridization of 114 independent cDNA clones with total rice genomic DNA showed 77 distinct and specific hybridization patterns. Of the 77 clones representing the above hybridization patterns, copies of 67 clones corresponding to 57 r-proteins could be estimated and, among these, only 6 clones were single copy, indicating that almost 90% of these r-proteins in rice were encoded by small multigene families. Loci of 36 r-protein genes could be mapped on the rice linkage map by using 30 full-length cDNA clone sequences from specific RFLP bands. Another 21 expressed gene loci were mapped using 3′ untranslated region specific cDNA probes amplified from the multicopy cDNA clones representing 17 of the r-protein multicopy gene families. The above 57 gene loci were mapped from 51 cDNA clones and 41 of these r-protein genes mapped to regions that did not show any clustering, while in 5 cases, pairs of r-protein genes cosegregated or linked closely. The r-protein genes in rice were located throughout the 12 chromosomes and it was found that more than one copy within a multigene family may be expressed simultaneously.Key words: rice, ribosomal protein, RFLP mapping, gene loci, multigene family.
Microsatellite sequences in a conifer,Pinus sylvestris
Authors: Kostia Silja , Varvio Sirkka-Liisa , Vakkari Pekka , Pulkkinen Pertti
Published: April 2011

Scots pine (Pinus sylvestris) genomic libraries were constructed and screened with oligonucleotide probes (GT)10, (CT)10, and (AT)10. Eight microsatellites were identified from 6000 clones screened. The longest microsatellite stretch found, (GT)9(N)21(AT)24, was amplified from bud and single pollen grain samples. In order to clarify the complex amplification pattern revealed, two PCR products were sequenced. The size differences were caused both by varying repeat numbers of the microsatellite stretches and by differences in other parts of the amplified sequence. This kind of complex molecular basis of microsatellite amplification within a species has not been previously reported. Microsatellite sequences were used as PCR primers to detect polymorphisms and to estimate the abundance of microsatellites.Key words: microsatellites, Pinus sylvestris, plant genome, inter SSR–PCR.
Families of tandemly repeated DNA elements from horse: cloning, nucleotide sequence, and organization
Authors: Broad T. E. , Lewis P. E. , Phua S. H. , Ede A. J. , Forrest J. W. , Pugh P. A.
Published: April 2011

DNA repeats, revealed initially by digestion of horse DNA with restriction enzymes, were cloned and characterized by cross-hybridization studies and nucleotide sequencing. The Sau-like family of tandem repeats contained two classes of repetitive elements with unit repeats of about 80 bp that shared no sequence similarity. Both unit repeats were present, frequently in tandem, in cloned segments of horse DNA of less than 600 bp. Evidence is presented, based on their ladderlike patterns of hybridization to horse DNA and their high level of similarity to published sequences of satellites from equine DNA, suggesting that they are centromerically located in the horse genome. The Sau-like tandem repeat families were specific to Equidae. Another class of repeats, GATA-like elements, which did not appear to have a centromeric distribution, was also cloned and sequenced.Key words: Equidae, Equus caballus, tandem DNA repeats, GATA-like repeats, Sau3AI repeats.
Collinearity between a 30-centimorgan segment ofArabidopsis thalianachromosome 4 and duplicated regions within theBrassica napusgenome
Authors: Cavell A C , Lydiate D J , Parkin IAP , Dean C , Trick M
Published: April 2011

Arabidopsis thaliana (the model dicotyledonous plant) is closely related to Brassica crop species. Genome collinearity, or conservation of marker order, between Brassica napus (oilseed rape) and A. thaliana was assessed over a 7.5-Mbp region of the long arm of A. thaliana chromosome 4, equivalent to 30 cM. Estimates of copy number indicated that sequences present in a single copy in the haploid genome of A. thaliana (n = 5) were present in 2-8 copies in the haploid genome of B. napus (n = 19), while sequences present in multiple copies in A. thaliana were present in over 10 copies in B. napus. Genetic mapping in B. napus of DNA markers derived from a segment of A. thaliana chromosome 4 revealed duplicated homologous segments in the B. napus genome. Physical mapping in A. thaliana of homologues of Brassica clones derived from these regions confirmed the identity of six duplicated segments with substantial homology to the 7.5-Mbp region of chromosome 4 in A. thaliana. These six duplicated Brassica regions (on average 22cM in length) are collinear, except that two of the six copies contain the same large internal inversion. These results have encouraging implications for the feasibility of shuttling between the physical map of A. thaliana and genetic maps of Brassica species, for identifying candidate genes and for map based gene cloning in Brassica crops.
Synaptonemal complex analysis in spermatocytes of white sturgeon,AcipensertransmontanusRichardson (Pisces, Acipenseridae), a fish with a very high chromosome number
Authors: Van Eenennaam A L , Murray J D , Medrano J F
Published: April 2011

The surface-spreading synaptonemal complex (SC) technique was used to visualize the process of chromosome synapsis in white sturgeon spermatocytes. Pachytene nuclei had various numbers of univalents (0-3) and self-paired foldback elements with no obvious centromeric region (1-7) that may represent accessory chromosomes. The total SC length was 482 ( ±56) µm and the average number of SC elements per nucleus was 139 ( ±3.4). This SC number suggests a higher chromosome number than had been reported in previous mitotic studies (2n = 248 ± 8). There was variation in the SC count both within and between animals. A representative SC karyotype is presented and some differences between the mitotic and meiotic karyotypes for this species are discussed. There was no evidence of multivalent formation, suggesting that the process of diploidization has gone to completion in the males of this ancient polyploid species. Each SC had lateral elements of equal length, and no bivalent exhibited the atypical pairing behavior that is often characteristically associated with heteromorphic sex chromosomes, suggesting that the male is not the heterogametic sex in white sturgeon.
Development of sequence characterized DNA markers linked to a dominant verticillium wilt resistance gene in tomato
Authors: Kawchuk L M , Hachey J , Lynch D R
Published: April 2011

Sequences were determined for codominant RAPD markers closely linked to the Ve locus, a dominant verticillium wilt resistance gene in tomato. Analysis of the sequences linked to Ve and ve revealed a perfectly homologous sequence with a central polymorphic region comprising 79 nucleotide substitutions, insertions, and deletions. Codominant and allele-specific SCARs were developed using conserved and polymorphic sequences linked to the Ve locus. High resolution linkage analysis using F2progeny segregating for resistance and marker-assisted selection indicated that linkage between the genetic markers and the Ve locus is less than 0.67 ± 0.49 cM. Sequences were useful in determining the molecular structure of a polymorphic genomic region closely linked to the Ve locus and in developing genetic markers that facilitated marker-assisted selection of the resistant, susceptible, heterozygous, and homozygous genotypes.
The nuclear ribosomal DNA intergenic spacers of wild and cultivated soybean have low variation and cryptic subrepeats
Authors: Nickrent Daniel L , Patrick Jennifer A
Published: April 2011

The intergenic ribosomal DNA spacers (IGSs) from cultivated soybean (Glycine max) and wild soybean (Glycine soja) were sequenced and compared with six other legumes. These IGS sequences were 1821 bp in length in G. soja and G. max cultivars Arksoy, Ransom, and Tokyo, and 1823 bp long in the G. max cultivar Columbus. These represent the smallest published plant IGS sequences to date. Two clones from each of the above five cultivars were sequenced and only 22 sites (1.2%) were polymorphic, thereby supporting previous work that showed low genetic variation in cultivated soybean. The amount of variation observed between different clones derived from the same individual was equal to the amount seen between different cultivars. The soybean IGS sequence was aligned with six other published legume sequences and two homologous regions were identified. The first spans positions 706-1017 in the soybean IGS sequence and ends at a putative promoter site that appears conserved among all legumes. The second is located within the 5' external transcribed spacer, spans positions 1251-1823 in soybean, and includes sequences first identified as subrepeats IV-1 and IV-2 in Vicia angustifolia. Sequences homologous to these two subrepeats were identified among all legume species examined and are here designated "cryptic subrepeats" (CS-1, CS-2) given the range in similarity value (79-96% for CS-1 and 60-95% for CS-2). Comparisons of CS-1 and CS-2 sequences within individual species show that divergence (substitutional mutations, insertions, and deletions) is sufficiently high to obscure recognition of the repeat nature of these sequences by routine dot plot analytical methods. The lack of subrepeats in the 5' half of the soybean IGSs raises questions regarding the role they play in transcription termination or enhancement.Key words: Glycine, Fabaceae, ribosomal DNA, promoter.
Direct PCR-based genetic mapping of rice telomeric repeat associated sequences
Authors: Shen Lishuang , Zhu Lihuang
Published: April 2011

Direct PCR-based genetic mapping of telomeric repeat associated sequences (TASs) was achieved using a RAPD primer mediated asymmetric PCR method. Twenty-two TAS loci were mapped in a rice doubled haploid population derived from a cross between an indica variety (Zhaiyeqing8) and a japonica variety (Jingxi17). Of these, 11 loci were mapped to the most distal position of seven chromosome arms and lengthened the linkage groups by 7.4-22.6 cM, five were mapped to the approximate positions of the centromeric regions, and six were mapped to other interstitial chromosomal regions.Key words: rice, Oryza sativa L., genetic mapping, telomeric repeat, telomeric repeat associated sequences, RAPD primer mediated PCR.
A species-specific satellite DNA from the entomopathogenic nematodeHeterorhabditis indicus
Authors: Abadon Monique , Grenier Eric , Laumond Christian , Abad Pierre
Published: April 2011

An AluI satellite DNA family has been cloned from the entomopathogenic nematode Heterorhabditis indicus. This repeated sequence appears to be an unusually abundant satellite DNA, since it constitutes about 45% of the H. indicus genome. The consensus sequence is 174 nucleotides long and has an A + T content of 56%, with the presence of direct and inverted repeat clusters. DNA sequence data reveal that monomers are quite homogeneous. Such homogeneity suggests that some mechanism is acting to maintain the homogeneity of this satellite DNA, despite its abundance, or that this repeated sequence could have appeared recently in the genome of H. indicus. Hybridization analysis of genomic DNAs from different Heterorhabditis species shows that this satellite DNA sequence is specific to the H. indicus genome. Considering the species specificity and the high copy number of this AluI satellite DNA sequence, it could provide a rapid and powerful tool for identifying H. indicus strains.Key words: AluI repeated DNA, tandem repeats, species-specific sequence, nucleotide sequence analysis.
Construction of a genetic linkage map and identification of AFLP markers for resistance to root-knot nematodes in peach rootstocks
Authors: Lu Zhen-Xiang , Sosinski B , Reighard G L , Baird W V , Abbott A G
Published: April 2011

A genetic linkage map for peach (Prunus persica (L.) Batsch) rootstocks has been constructed using amplified fragment length polymorphism (AFLP) markers in 55 F2individuals derived from the cross Lovell x Nemared. From 21 different primer combinations, a total of 169 AFLP markers were scored, of which, 153 were assigned to 15 linkage groups covering 1297 centimorgans (cM) of the peach nuclear genome. The average interval between these markers was 9.1 cM. Two genes (Mi and Mij) involved in resistance to root-knot nematodes (Meloidogyne incognita (Kofoid and White) Chitwood and Meloidogyne javanica (Treub) Chitwood) were mapped to a single linkage group (Group I). These two loci were separated by a 16.5-cM interval. One codominant AFLP marker (EAA/MCAT10) was tightly linked to the Mij locus (3.4 cM), and a dominant AFLP marker (EAT/MCAT2) was found to be closely associated with the Mi locus (6.0 cM). These markers are being studied for utilization in peach rootstock breeding with marker-assisted selection.Key words: peach rootstocks, root-knot nematodes, resistance, AFLP, mapping.
Molecular cytogenetic studies in rubber,Hevea brasiliensisMuell. Arg. (Euphorbiaceae)
Authors: Leitch Andrew R , Lim K Yoong , Leitch Ilia J , O'Neill Michelle , Chye MeeLen , Low FeeChon
Published: April 2011

This paper reports the start of a molecular cytogenetics programme targeting the genome of the angiosperm tree species Hevea brasiliensis Muell. Arg. (rubber, 2n = 36), a major world crop about whose genetics very little is known. A metaphase karyotype of rubber is presented. In situ hybidization with the probe pTa71 for ribosomal DNA (rDNA) shows that there are four sites of probe hybidization occurring on two pairs of chromosomes called chromosomes 6 and 7 carrying sites NOR-1 and NOR-2, respectively. An examination of meristematic interphase nuclei shows that all four loci have the potential to be partially decondensed at interphase, although in many nuclei one or more loci appear fully condensed and apparently inactive. The probe pXVI revealed a single pair of chromosomes carrying 5S rDNA. The probes pTa71 and pXVI provide cytogenetic markers for three pairs of chromosomes that will be of use in genetic mapping programmes. The rubber chromosomes also have telomere sequences that hybridize with the Arabidopsis consensus sequence TTTAGGG. With the exception of the satellite region containing rDNA, which fluoresces brightly with chromomycin A3, fluorescence banding showed that there is no strong demarcation of the genome into GC- and AT-rich regions, as occurs in mammalian genomes.Key words: rubber, Hevea, genetic mapping, cytogenetics, ribosomal DNA, rDNA fluorescence banding.
Isolation and characterisation of repeated DNA sequences from Erianthus spp. (Saccharinae: Andropogoneae)
Authors: Besse P , McIntyre C L
Published: April 2011

Four anonymous noncoding sequences were isolated from Erianthus arundinaceus. The four sequences were selected because they were specific to the genusErianthus section Ripidium, relative to Saccharum spp. These sequences, designated Eracsi 294, 228, 153, and 34, showed various degrees of repetitiveness and different patterns of distribution. Eracsi 34 and 153 were low- and medium-copy repeated sequences, respectively, and appeared to be present at discrete locations in the Erianthus genome. By contrast, Eracsi 294, also a low-copy sequence, appeared to be more dispersed in location, with some tandem arrays identified. Eracsi 228 was highly repeated and dispersed. The location of Eracsi 228 was more precisely determined by FISH and was found to be distributed along the length of, but not at the telomeres of, most chromosomes in two Erianthus species. The distribution of the four sequences was investigated in a sample of 65 Erianthus (representing 9 species) and 14 Saccharum (2 species) accessions. The usefulness of these sequences for phylogenetic and genome organisation studies in sugarcane and for assessing the genetic structure of Saccharum x Erianthus intergeneric hybrids is discussed.Key words: Erianthus, FISH, repetitive sequences, Saccharum, sugarcane.
Nuclear DNA content of 11 fungal species in Glomales
Authors: Hosny Michel , Gianinazzi-Pearson Vivienne , Dulieu Hubert
Published: April 2011

The nuclear DNA content of 11 species of Glomales was evaluated by flow cytometry after DAPI staining relative to Gigaspora margarita, which was used as internal standard. The nuclear DNA content of this species was calibrated by propidium iodide staining relative to chicken red blood cells. A correction was applied when the difference in AT content of the DNA was significant between a sample and the standard. A single unimodal peak of fluorescence was observed for nuclei from the quiescent spores of the 11 fungal species studied. It was considered that this peak corresponded to the amount of DNA in the genome of each species. Important interspecific variations in DNA content per nucleus (1- to 8-fold) were observed among four species of the genus Scutellospora.Key words: nucleus, DNA content, flow cytometry, spore, Glomales.