bluuebunny/crossref_metadata_2025 huggingface dataset:
TheDrosophila montiumsubgroup species. Phylogenetic relationships based on mitochondrial DNA analysis
Authors: Nikolaidis Nikolas , Scouras Zacharias G.
Published: May 2008

Mitochondrial DNA (mtDNA) restriction site maps for three Drosophila montium subgroup species of the melanogaster species group, inhabiting Indian and Afrotropical montium subgroup territories, were established. Taking into account previous mtDNA data concerning six oriental montium species, a phylogeny was established using distance-matrix and parsimony methods. Both genetic diversity and mtDNA size variations were found to be very narrow, suggesting close phylogenetic relationships among all montium species studied. The phylogenetic trees that were constructed revealed three main lineages for the montium subgroup species studied: one consisting of the Afrotropical species Drosophila seguyi, which is placed distantly from the other species, one comprising the north-oriental (Palearctic) species, and one comprising the southwestern (south-oriental, Australasian, Indian, and Afrotropical) species. The combination of the mtDNA data presented here with data from other species belonging to the melanogaster and obscura subgroups revealed two major clusters: melanogaster and obscura. The melanogaster cluster is further divided into two compact lineages, comprising the montium subgroup species and the melanogaster complex species; the species of the other complex of the melanogaster subgroup, yakuba, disperse among the obscura species. The above grouping is in agreement with the mtDNA size variations of the species. Overall, among all subgroups studied, the species of the montium subgroup seem to be the most closely related. Key words : mtDNA restriction site maps, mtDNA size variations, Drosophila, phylogeny.
Comparison of the mitotic karyotypes of Ceratitis capitata, Ceratitis rosa, and Trirhithrum coffeae (Diptera: Tephritidae) by C-banding and FISH
Authors: Willhoeft Ute , Franz Gerald
Published: May 2008

The sex chromosomes of the tephritid fruit fly Ceratitis capitata (Wiedemann) are heteromorphic. The male-determining region was located on the Y chromosome by deletion mapping using unbalanced offspring from several translocation strains. In addition, we showed that only 15% of the Y chromosome is required for male determination and male fertility. Based on this result, we expected to find Y-chromosomal length polymorphism in natural populations. Using fluorescence in situ hybridization with two repetitive DNA probes that label the Y chromosome, no obvious size differences were detected in seven wild-type strains and three mutant strains. As the medfly is probably of East African origin, we also analyzed two wild-type strains established recently from pupae sampled in Kenya. The Y chromosomes show a polymorphism in the hybridization pattern of a repetitive Y-specific medfly clone. However, the overall size of the Y chromosome is similar to that of the other strains. Besides C. capitata, the tephritid fruit flies Ceratitis (Pterandrus) rosa Karsch and Trirhithrum coffeae Bezzi also emerged from pupae sampled in Kenya. Their karyotype was analyzed by C-banding. Furthermore, the ribosomal genes were mapped to the sex chromosomes in these two species. Key words : Ceratitis capitata, Tephritidae, C-Banding, FISH, rDNA.
Dosage effects on morphological and quantitative traits in maize aneuploids
Authors: Lee E. A. , Darrah L. L. , Coe E. H.
Published: May 2008

Dosage effects generated by either loss or gain of a chromosome segment were used to identify chromosome regions associated with morphological and quantitative characters in maize (Zea mays L.). Using B–A translocation stocks introgressed into a B73Ht background, a chromosome arm dosage series in a Mo17Ht × B73Ht F1hybrid background was created for 18 of the 20 chromosome arms. The dosage series was then evaluated for 12 quantitatively inherited characters to associate specific phenotypic changes in a trait with a specific chromosome arm. Not only did our results show the familiar aneuploid syndrome phenomenon, but differential dosage effects among particular chromosome arms were demonstrated. All the quantitative traits measured and all the chromosome arms examined in this study were responsive to changes in chromosome arm dosage. The possible bases behind those differences and their utility in identifying quantitative trait loci, as well as the genetic relationships among the group of quantitatively inherited characters studied, are considered. Key words : corn, chromosome arm, B–A translocations, dosage analysis.
Evolutionary rate variation withinMus APRT
Authors: Fieldhouse Dan , Golding G. Brian
Published: May 2008

Rodents are thought to have relatively high rates of evolution, twice as fast as the rates for mammals in other orders. However, the uniformly high rates of evolution inferred for the order Rodentia from Mus musculus and Rattus norvegicus are not consistently found for other rodent species. Using a maximum likelihood phylogenetic algorithm (DNAML), we show here that Mus spicilegus has a fivefold different rate of evolution in 1100 bp around the adenine phosphoribosyltransferase gene (APRT) since its divergence from a common ancestor with Mus musculus. A greater than threefold difference in rates is also found in a comparison of the number of evolutionary events directly detected from the APRT sequences of these two closely related Mus species. The evolutionary events can be directly detected, since M. spicilegus, M. musculus, and the four rodent outgroup species used to determine the ancestral sequence are so closely related. One of the major differences between M. spicilegus and M. musculus that might affect evolutionary rate is the degree of commensalism with man. The Mus species therefore provide a useful model for testing various hypotheses for the causes of rate variations between genes, and possibly, between lineages. Key words : rate, variation, rodent, Mus spicilegus, Mus musculus.
Microprotoplast-mediated transfer of single specific chromosomes between sexually incompatible plants
Authors: Ramulu K. S. , Dijkhuis P. , Rutgers E. , Blaas J. , Krens F. A. , Dons J. J. M. , Colijn-Hooymans C. M. , Verhoeven H. A.
Published: May 2008

Microprotoplast-mediated chromosome transfer (MMCT) through fusion of small (subdiploid) microprotoplasts of a transgenic triploid potato (Solanum tuberosum) cell line with leaf protoplasts of tobacco (Nicotiana tabacum) and the wild tomato species Lycopersicon peruvianum is reported. The microprotoplasts contained one or a few chromosomes. Monosomic addition plants were produced from the fusion products. We employed mass-scale induction of micronuclei in donor suspension cells of potato using the microtubule inhibitor Cremart. Protoplasts were isolated from micronucleated cells after incubation in a cell wall digesting enzyme mixture. The microprotoplasts were isolated from the micronucleated protoplasts by high-speed centrifugation. By using sequential filtration, small microprotoplasts containing one or few chromosomes were separated from the bigger subdiploid microprotoplasts. These small microprotoplasts were fused with recipient protoplasts of tobacco or tomato using polyethylene glycol. The selectable marker kanamycin resistance (KanR) and the reporter gene β-glucuronidase (gus), carried by the donor potato chromosome, were used for the selection of fusion products and the isolation of hybrid calli. Several monosomic addition plants were obtained within the short period of 3–4 months after fusion. These contained one potato chromosome carrying a single copy of gus and one or two copies of the neomycin phosphotransferase (nptII) gene conferring KanR, and the complete set of chromosomes of tobacco or tomato, as revealed by genomic in situ hybridization and Southern blot hybridization. The alien genes, gus and nptII, were stably expressed in both the tobacco and tomato backgrounds. They were transmitted to the progeny after backcrossing to tomato. Monosomic and disomic additions, and some introgression plants showing integration of gus and nptII in the tomato genome, were recovered in the first backcross progeny. The potential value of MMCT for the transfer of economically important traits, genome analysis, and gene expression is discussed. Key words : chromosome transfer, microprotoplast fusion, monosomic–disomic additions, sexual transmission, DNA integration, alien gene expression.
A minisatellite polymorphism in intron III of the barramundi (Lates calcarifer) growth hormone gene
Authors: Yowe David L. , Epping Ronald J.
Published: May 2008

This paper describes the detection of a polymorphism within the growth hormone (GH) gene of the fish barramundi (Lates calcarifer). PCR amplification of barramundi genomic DNA generated three different sized products: A, 409 bp; B, 478 bp; and H, 520 bp. Each barramundi isolate displayed one of four different types of profiles, which contained specific combinations of these PCR products. Sequence analysis confirmed that products A and B are different forms of the barramundi GH gene, and studies showed that product H was an artifact due to heteroduplex formation between the two smaller-sized molecules. The polymorphic nature of these PCR products was due to differences in the number of repeat monomers within the 5′ end of the barramundi decaminisatellite, an AT-rich repetitive sequence that was identified within intron III of this gene. The barramundi decaminisatellite consisted of 24 or 28 10-nucleotide imperfect direct repeat monomers in a tandem array. The monomers were grouped into one of three different families and evidence for monomer homogenization by crossover fixation was presented. The barramundi decaminisatellite differed from previously reported AT- or GC-rich minisatellites, although a similar decaminisatellite has been identified in intron III of the tilapia GH gene. Key words : mutation, PCR, somatotropin, teleost fish, variable number tandem repeat, VNTR.
Characterization of heterochromatic regions in 'Trovita' orange (Citrus sinensis Osbeck) chromosomes by the fluorescent staining and FISH methods
Authors: Matsuyama Tomoki , Akihama Tomoya , Ito Yuji , Omura Mitsuo , Fukui Kjichi
Published: May 2008

CMA/DAPI double staining and FISH methods using rDNA and telomere specific repeated sequences as probes were applied to characterize the large amount of heterochromatin in the telomeric regions of 'Trovita' orange (Citrus sinensis Osbeck) chromosomes. As a result, all the heterochromatic regions were CMA+/DAPI–, and thus were GC rich. Three CMA+/DAPI– heterochromatic regions were positive to the 26S rDNA probe. Telomere arrays consisting of Tm(A)Gn were detected on the extreme ends of each chromosome and most of the CMA+/DAPI – heterochromatic regions were ordered close inside the telomere-specific repeated sequences. The data obtained in this study will be useful for karyotyping, systematics, and molecular analysis of orange chromosomes. Key words : Citrus, rDNA, telomere repeated sequence, FISH, CMA/DAPI staining, heterochromatin.
Comparison off genetic distance and order off DNA markers in five populations of rice
Authors: Antonio B. A. , Inoue T. , Kajiya H. , Nagamura Y. , Kurata N. , Minobe Y. , Yano M. , Nakagahra M. , Sasaki T.
Published: May 2008

A group of about 300 evenly distributed DNA markers from a high density RFLP linkage map of rice constructed using an F2population derived from a japonica variety, Nipponbare, and an indica variety, Kasalath, were used to evaluate gene order and genetic distance in four other rice mapping populations. The purpose of this study was to determine the degree to which information gained from the high density linkage map could be applied to other mapping populations, particularly with regard to its utility in bridging quantitative traits and molecular and physical mapping information. The mapping populations consisted of two F2populations derived from Dao Ren Qiao/Fl-1084 and Kinandangputi/Fl-1007, recombinant inbred lines from Asominori/IR24, and a backcross population from Sasanishiki/Habataki//Sasanishiki. All DNA markers commonly mapped in the four populations showed the same linkage groups as in the Nipponbare/Kasalath linkage map with conserved linkage order. The genetic distance between markers among the different populations did not vary to a significant level in any of the 12 chromosomes. The differences in some markers could be attributed to the size of the population used in the construction of the linkage maps. Furthermore, the conservation of linkage order found in the distal region of chromosomes 11 and 12 was also confirmed in the RFLP maps based on the four populations of rice. These suggest that any major genetic information from the Nipponbare/Kasalath map can be expected to be approximately the same in other crosses or populations. This high density RFLP linkage map, which is being utilized in constructing a physical map of rice, can be very useful in interpreting genome structure with great accuracy in other populations. Key words : linkage map, japonica, indica, gene order, genetic distance.
Level of polymorphism and genetic mapping of AFLP markers in rice
Authors: Mackill D. J. , Zhang Z. , Redoña E. D. , Colowit P. M.
Published: May 2008

Amplified fragment length polymorphism (AFLP) has been proposed as a valuable tool for gene mapping in plant species. We compared the levels of polymorphism for AFLP, RAPD, and microsatellite markers on 12 japonica and 2 indica rice cultivars. For AFLPs, seven EcoRI and seven MseI primers used in 18 primer combinations generated a total of 529 bands, of which 147 were clearly polymorphic among the accessions. The 21 RAPD primers produced 103 bands of which 43 were polymorphic. For the microsatellite markers the number of alleles per locus ranged from one (1 locus) to six. All marker types gave the same classification of the rice accessions into subspecies. Within japonica cultivars, the average percent polymorphism between any two accessions was 22% for AFLP, 24% for RAPD, and 36% for microsatellite markers (monomorphic bands excluded). The average percent polymorphism between indica and japonica accessions was 65, 35, and 76%, for AFLP, RAPD, and microsatellite markers, respectively. The total number of polymorphic bands was much higher for AFLPs, averaging over eight per gel. Seven AFLP primer combinations were assayed on 80 F2plants of an indica × japonica cross previously mapped with RFLP markers. Of 54 AFLP bands scored, 50 could be mapped to specific chromosomes, and these appeared to be distributed throughout the rice genome. This indicates that AFLPs are a promising marker for mapping important genes in rice. Key words : Oryza sativa, AFLP, genetic mapping, polymorphism.
A rapid antibody-based test for Sec-2, a marker for the short arm of chromosome 2 of rye (2RS)
Authors: Skerritt J. H. , Gupta R. B. , Andrews J. L. , Stoddard F. L. , Howes N. K.
Published: May 2008

A simple monoclonal antibody-based screening test has been developed for the presence of translocations of the short arm of chromosome 2 of rye (2RS) with wheat chromosome 2B. 2RS encodes a set of about three polypeptides known as Mr 75 000 gamma-secalins. Use of the antibody test for these secalins enabled screening of several hundred seeds per day. The antibody could readily distinguish 2BL–2RS translocations and 2R substitutions from 1BL–1RS translocations or nontranslocation wheats. Use of the antibody in analysis of segregating progeny for Sec-2 in several wheat backgrounds was successful. Results with a selection of the seed population were checked using protein gel electrophoresis, with 100% correct confirmation. Key words : rye, wheat, seed proteins, translocation, diagnostic test.
A physical map of theThinopyrum-derivedLr19translocation
Authors: Prins R. , Marais G. F. , Marais A. S. , Janse B. J. H. , Pretorius Z. A.
Published: May 2008

Twenty-nine lines with deletions in the Lr19 ('Indis') translocated chromosome segment were used to physically map three Thinopyrum RFLP loci as well as the Sr25 and Sd1 loci. From the data, the relative locations of marker loci on the translocation were determined as: Sd1, Xpsr165, Xpsr105, Xps129, Lr19, Wsp-D1, Sr25/Y. The data confirmed the reported homoeology between the Lr19 segment and chromosome arm 7DL of wheat. Also, it seems that the Lr19 translocation in 'Indis' is very similar to the Lr19 segment in the T4 source and that the former may not derive from Thinopyrum distichum. Key words : deletion mapping, leaf rust resistance.
Localization of the repetitive telomeric sequence (TTAGGG)nin four salmonid species
Authors: Abuín M. , Martínez P. , Sánchez L.
Published: May 2008

We have analyzed the localization of the highly conserved telomeric sequence (TTAGGG)nin four salmonid species, two of the genus Salmo (Salmo trutta and Salmo salar) and two of the genus Oncorhynchus (Onchorhynchus mykiss and Onchorhynchus kisutch), by fluorescent in situ hybridization. As expected, the hybridization signal was mostly localized at the telomeres of all chromosomes in the four species. Two species evidenced special hybridization sites with the telomeric probe: (i) interstitial heterochromatic blocks in particular long chromosomes in S. salar, this observation supports tandem fusions as the karyotypic evolutionary mechanism leading to the formation of the long acrocentric and submetacentric chromosomes in the karyotype of S. salar; (ii) the whole NOR region in O. mykiss; this observation suggests that the (TTAGGG)nsequence is scattered all along this chromosome region. Key words : Salmo, Oncorhynchus, telomeres, in situ hybridization, evolution.
Inheritance of random amplified polymorphic DNA markers in cassava (Manihot esculentaCrantz)
Authors: Gomez Rocio , Angel Fernando , Bonierbale Merideth W. , Rodriguez Fernando , Tohme Joseph , Roca William M.
Published: May 2008

The informativeness and inheritance of randomly amplified polymorphic DNA (RAPD) markers were investigated in an intraspecific F1progeny derived from two heterozygous parents. The analysis confirmed the utility of RAPD markers for comparing candidate parents for the development of a molecular genetic map, and provided numerous markers for linkage analysis in a crop with a very limited history of classical or molecular genetic studies. Six potential parental lines (themselves F1hybrid clones) showed between 1.82 and 0.62 segregating bands per primer in three hybrid families. Forty-three percent (309) of 722 primers produced polymorphic products in the most informative of these three crosses, revealing 328 single-dose (SD) markers segregating 1:1 for presence/absence in a progeny of 90 individuals. A second class of informative markers were those present in both parents but segregating in the progeny. Fifty-seven or 67% of the monomorphic but segregating markers exhibited the 3:1 ratio expected for SD dominant markers in a cross between heterozygotes. Linkage groups were constructed from the segregation of SD RAPD markers originating in the female (TMS 30572) and the male (CM2177-2) parent. Key words : RAPDs, molecular markers, genetic segregation, Manihot, single-dose markers.
Distribution and complex organization of satellite DNA sequences in Aveneae species
Authors: Grebenstein Bärbel , Grebenstein Oliver , Sauer Wilhelm , Hemleben Vera
Published: May 2008

Distribution, organization, and molecular analysis of four unrelated satellite DNA components in Aveneae species are described. Highly repeated DNA elements were cloned from Helictotrichon convolutum (CON1 and CON2) and Helictotrichon compression (COM1 and COM2). The lengths of the repeat monomers are 365 bp (CON1), 562 bp (CON2), 346 bp (COM1), and 476 bp (COM2). Similar repeats were detected by dot blots, Southern blots, and by DNA sequencing in other species of the genus Helictotrichon, in Aveneae species, and in species of the tribes Andropogoneae and Oryzeae. All four satellite DNAs are differently distributed in the taxonomic groups mentioned above. Remarkably, the longer elements are built up in a complex pattern of either shorter subrepeats arranged in tandem (COM2) or by duplications inserted into an original 369-bp element (CON2). Shorter representatives, 190 bp, similar to CON1 elements occur in Holcus species. In Koeleria species, COM1-related repeats are only 180 bp in length. No similarity was found among the sequences CON2, COM1, and COM2 or with sequences of other repetitive DNA elements of the grasses, but CON1 shows sequence similarity to an A genome specific repetitive DNA of Oryza (rice). Key words : genome evolution, grasses, Poaceae, repetitive DNA, wild oats.
Genetic mapping inEucalyptus urophyllaandEucalyptus grandisusing RAPD markers
Authors: Verhaegen Daniel , Plomion Christophe
Published: May 2008

Two single-tree linkage maps were constructed for Eucalyptus urophylla and Eucalyptus grandis, based on the segregation of 480 random amplified polymorphic DNA (RAPD) markers in a F1interspecific progeny. A mixture of three types of single-locus segregations were observed: 244 1:1 female, 211 1:1 male, and 25 markers common to both, segregating 3:1. Markers segregating in the 1:1 ratio (testcross loci) were used to establish separate maternal and paternal maps, while markers segregating in the 3:1 ratio were used to identify homology between linkage groups of the two species maps. An average of 2.8 polymorphic loci were mapped for each arbitrary decamer primer used in the polymerase chain reaction. The mean interval size beween framework markers on the maps was 14 cM. The maps comprised 269 markers covering 1331 cM and 236 markers covering 1415 cM, in 11 linkage groups, for E. urophylla (2n = 2x = 22) and E. grandis (2n = 2x = 22), respectively. A comparative mapping analysis with two other E. urophylla and E. grandis linkage maps showed that RAPDs could be reliable markers for establishing a consensus species map. RAPD markers were automatically and quantitatively scored with an imaging analyzer. They were classified into four categories based on their optical density. A fragment intensity threshold is proposed to optimize the selection of reliable RAPD markers for future mapping experiments. Key words : genetic linkage map, Eucalyptus urophylla, Eucalyptus grandis, random amplified polymorphic DNA, RAPD, automated data collection.
Nucleotypic influences on chromosome-specific chiasma variation inCrepis capillaris. I. Responses to early colchicine treatment and chromosome doubling
Authors: Abberton M. T. , Callow R. S.
Published: May 2008

Additive and multiplicative effects of colchicine treatment at the seedling stage and of chromosome doubling on chromosome-specific chiasma frequency at metaphase I have been measured in comparisons between C0and untreated diploids and between C0autotetraploids and C0diploids. Early colchicine treatment increases the frequency of chromosome C univalents to 1.8% but has no similar effect on chromosomes A and D. Colchicine treatment has little net effect on mean chiasma frequency, deducting an average of 0.204 chiasmata per set but otherwise multiplying the mean by a factor of 1.182. These additive and multiplicative effects represent averages of six phenotypes. Chromosome doubling in a tetraploid–diploid chimaera subtracts an average of 0.265 chiasmata per set but otherwise doubles the numbers of chiasmata at the diploid level (× 2.134). Comparison of six diploids and tetraploids reveals modest average additive (+ 1.103) and multiplicative effects (× 1.190). The implications of these findings are discussed in the light of new analyses of previously published data. Key words : chiasmata, Crepis, colchicine, meiosis, polyploidy.
Genetic and contig map of a 2200-kb region encompassing 5.5 cM on chromosome 1 ofArabidopsis thaliana
Authors: Hardtke Christian S. , Berleth Thomas
Published: May 2008

In the course of the isolation of the MONOPTEROS (MP) gene, required for primary root formation in Arabidopsis thaliana, a yeast artificial chromosome (YAC) contig encompassing approximately 2200 kilobases corresponding to 5.5 cM on the top arm of chromosome 1 was established. Forty-six YAC clones were characterized and 12 new restriction fragment length polymorphism (RFLP) markers are presented. Three new codominant amplified polymorphic sequence (CAPS) markers were generated that enabled high resolution genetic mapping and correlation of physical and genetic distances along the contig. The map contributes to the completion of a physical map of the Arabidopsis genome and should facilitate positional cloning of other genes in the region as well as studies on genome organization. We also present another set of 11 physically linked probes, as well as mapping data for additional RFLP markers within a broader interval of 10.4 cM. Key words : Arabidopsis, CAPS markers, MONOPTEROS gene, physical map, RFLP markers, YAC contig.
A study of 28Elymusspecies using repetitive DNA sequences
Authors: Svitashev Sergei , Salomon Björn , Bryngelsson Tomas , Bothmer Roland von
Published: May 2008

Four repetitive DNA sequences cloned from the barley (Hordeum vulgare) genome and common for different Triticeae species were used for a molecular study of phylogenetic relationships among 28 Elymus species. Two wild Hordeum species (H genome), two Pseudoroegneria species (S genome), Agropyron cristatum (P genome), and Australopyrum velutinum (W genome) were included as genomic representatives for the genomes that supposedly were involved in the evolution of the genus Elymus. Our results are essentially congruent with the genomic classification system. This study demonstrates that Elymus is not a monophyletic genus. Based on an analysis of Southern blot hybridization we could discriminate between SY and SH species owing to the strong specific hybridization pattern of the H genome. Hexaploid SYH species gave a hybridization pattern similar to SH species for the same reason. The results support the genomic composition of Elymus batalinii as SYP and also indicated the presence of at least one H genome in Elymus enysii with a hitherto unknown genomic constitution. Elymus erianthus had a hybridization pattern distinctly different from all other species in the investigation. Key words : Elymus, RFLP, phylogeny, repetitive DNA.
Characterization of microsatellite markers in eastern white pine
Authors: Echt C. S. , May-Marquardt P. , Hseih M. , Zahorchak R.
Published: May 2008

An enrichment cloning method was evaluated for the isolation of microsatellite loci from eastern white pine and the resulting markers were examined for polymorphisms. A 200-fold enrichment was achieved for highly abundant (AC)nrepeats, but for much less abundant (ACAG)nrepeats an enrichment of only 20-fold was obtained. Using a single set of PCR conditions, 19 microsatellite loci were identified from 77 primer pairs evaluated. Genotyping of 16 (AC)nloci in 16 unrelated white pines from the north-central United States revealed an average of 5.4 alleles per locus and an average observed heterozygosity of 0.515. Five loci were scored among megagametophytes from a single pine to obtain a haploid genotype of the segregating female meiotic products. All loci segregated according to Mendelian expectations and linkage was established for two of the loci. It was concluded that (AC)nloci are highly variable in this species and that SSR (simple sequence repeat) markers can be efficiently developed for genome mapping and population genetics studies. Key words : Pinus strobus, forest genetics, simple sequence repeat, SSR, allelic diversity.
Extraordinarily polymorphic ribosomal DNA in wild and cultivated rice
Authors: Liu K. D. , Zhang Qifa , Yang G. P. , Maroof M. A. Saghai , Zhu S. H. , Wang X. M.
Published: May 2008

A collection of 481 rice accessions was surveyed for ribosomal DNA (rDNA) intergenic spacer length polymorphism to assess the extent of genetic diversity in Chinese and Asian rice germplasm. The materials included 83 accessions of common wild rice, Oryza rufipogon, 75 of which were from China; 348 entries of cultivated rice (Oryza sativa), representing almost all the rice growing areas in China; and 50 cultivars from South and East Asia. A total of 42 spacer length variants (SLVs) were detected. The size differences between adjacent SLVs in the series were very heterogeneous, ranging from ca. 21 to 311 bp. The 42 SLVs formed 80 different rDNA phenotypic combinations. Wild rice displayed a much greater number of rDNA SLVs than cultivated rice, while cultivated rice showed a larger number of rDNA phenotypes. Indica and japonica groups of O. sativa contained about equal numbers of SLVs, but the SLV distribution was significantly differentiated: indica rice was preferentially associated with longer SLVs and japonica rice with shorter ones. The results may have significant implications regarding the origin and evolution of cultivated rice, as well as the inheritance and molecular evolution of rDNA intergenic spacers in rice. Key words : rDNA, Oryza rufipogon, Oryza sativa, germplasm diversity, evolution.
Assignment of a gene(s) conferring apomixis inTripsacumto a chromosome arm: cytological and molecular evidence
Authors: Kindiger B. , Bai D. , Sokolov V.
Published: May 2008

Attempts are underway to locate and transfer genes conferring diplosporous apomixis from Tripsacum to maize. The objective of this study was to evaluate several apomictic and sexual maize–Tripsacum hybrids for the presence or absence of Tripsacum chromosomes, PCR–RAPD generated markers, and RFLP markers that would have an association with apomictic development. Cytological and molecular analysis resulted in the identification of the Tripsacum chromosome arm carrying the gene(s) conferring diplosporous apomixis. Evaluations made on apomictic sexually derived maize + Tripsacum addition lines and an apomictic line possessing a Mz6L–Tr16L translocation were used to establish the location of the gene(s). Results of the study indicate that the successful transfer of a single Tripsacum chromosome is all that is necessary to maintain apomictic reproduction in a maize background. Additional use of this material may facilitate the development of an apomictic maize prototype and the eventual isolation of the gene(s). Key words : apomixis, Tripsacum, mapping, maize.
Prediction of heterosis in wheat using coefficient of parentage and RFLP-based estimates of genetic relationship
Authors: Barbosa-Neto J. F. , Sorrells M. E. , Cisar G.
Published: May 2008

Genetic relationship can be a useful predictor of the relative performance of hybrid combinations for a hybrid breeding program resulting in reduced time and cost of hybrid testing. Genetic relationships of 112 wheat (Triticum aestivum L. em. Thell.) lines were estimated using 41 DNA clones hybridizing to 273 DNA fragments and by calculating coefficient of parentage (COP). Heterosis was estimated for 722 hybrids grown in multiple locations, with 189 being tested in more than 1 year. The average RFLP (restriction fragment length polymorphism) based genetic distance index (DI) was 0.35. Midparent heterosis for grain yield ranged from −20 to 57% and high-parent heterosis from −22 to 47%. The correlation between RFLP-based estimates of genetic distance and COP was nonsignificant (−0.33). Coefficient of parentage was significantly correlated with heterosis for all traits in 1991 but not in other years. Genetic distance based on RFLPs scored in this study was not correlated with heterosis in any of the years tested. Further refinement of gene pools and new prediction methods will be required to facilitate the exploitation of genetic variability for hybrid wheat improvement. Key words : wheat, heterosis, genetic distance.
Genome differentiation inAegilops. 2. Physical mapping of 5S and 18S–26S ribosomal RNA gene families in diploid species
Authors: Badaeva Ekatherina D. , Friebe Bernd , Gill Bikram S.
Published: May 2008

The distribution of the 5S and 18S–5.8S–26S (18S–26S) ribosomal RNA (rRNA) gene families on chromosomes of all diploid Aegilops species was studied by in situ hybridization with pTa71 (18S–26S rDNA) and pTa794 (5S rDNA) DNA clones. One major 18S–26S rDNA locus was found in the nucleolus organizer region (NOR) of each of the species Aegilops tauschii and Aegilops uniaristata and two loci were detected in the remaining species. In addition to major NORs, from one to nine minor loci were observed; their numbers and chromosomal locations were species-specific. Some minor loci were polymorphic, whereas others were conserved. One or two 5S rDNA loci were observed in the short arms of the chromosomes of groups 1 and 5 of all diploid Aegilops species except Ae. uniaristata, where one 5S rDNA site was located in the distal part of the long arm of chromosome 1N. The 5S rDNA loci were not associated with NORs; however, the relative positions of two ribosomal RNA gene families were diagnostic for chromosomes of homoeologous groups 1, 5, and 6. Implications of these results for establishing phylogenetic relationships of diploid Aegilops species and mechanisms of genome differentiation are discussed. Key words : wheat, Triticum, Aegilops, 5S rRNA, 18S–26S rRNA, in situ hybridization, evolution.
Hygromycin-resistant calli generated by activation and excision of maize Ac/Ds transposable elements in diploid and hexaploid wheat cultured cell lines
Authors: Takumi Shigeo
Published: May 2008

To investigate the activation and transposition of maize transposable elements in wheat cultured cells, plasmid DNAs containing the maize Ac/Ds elements located between the CaMV 35S promoter and a hygromycin B resistance gene (hph) were introduced into two wheat (Triticum aestivum and Triticum monococcum) cultured cell lines by microprojectile bombardment. In the first experiment, hph was activated by excision of the Ac element, which encodes transposase, in the two wheat cell lines. In the second experiment, the Ds element was excised by a stabilized Ac element, lacking inverted repeats of the Ac element and located on another plasmid, and therefore leading to activation of hph. After selection of bombarded cells by hygromycin B, many resistant calli were recovered in both wheat cell lines. The integration of hph and the Ac transposase gene was confirmed by PCR and genomic Southern analysis. The stable expression of hph and the transposase gene was also assessed by Northern blot and reverse transcriptase PCR analysis, respectively. Moreover, characteristic sequence alterations were found at Ac/Ds excision sites. These findings indicate that the maize Ac/Ds transposable elements are activated and excised by expression of the Ac transposase gene in both diploid and hexaploid wheat cells. Key words : transposable elements, excision site, transgenic wheat callus, particle bombardment, Ac/Ds.
Negative regulation of gene expression of a novel proline-, threonine-, and glycine-rich protein by water stress in Lycopetsicon chilense
Authors: Yu Long-Xi , Tabaeizadeh Zohreh , Chamberland Hélène , Lafontaine Jean G.
Published: May 2008

We have isolated a full length cDNA clone (designated PTGRP) encoding a proline-rich protein from leaves of Lycopersicon chilense. Sequence analysis of the 552-bp insert revealed that the open reading frame encodes a 12.6-kDa protein. The deduced amino acid sequence of PTGRP consists of a C-terminal proline-rich domain with two identical repeat motifs Phe-Pro-Met-Pro-Thr-Thr-Pro-Ser-Thr-Gly-Gly-Gly-Phe-Pro-Ser. The N terminus lacks proline and is hydrophobic. Unlike other proline-rich proteins this protein contains five glycine-rich repeat motifs (Gly-X)n representative of glycine-rich proteins. Southern blot analysis showed that PTGRP is a member of a small gene family within the L. chilense genome. Northern blot experiments revealed that the PTGRP gene is significantly down regulated by water stress. PTGRP mRNA transcription decreased 5- to 10-fold in leaves and stems after 4–8 days of water stress. The mRNA reaccumulated when the drought-stressed plants were rewatered. The in situ hybridization experiments also revealed that PTGRP mRNAs were more abundant in leaf sections of plants watered regularly compared with those of plants submitted to water stress. Down regulation of the PTGRP gene was also observed in desiccated cell suspensions of L. chilense and in those treated with abscisic acid, mannitol, and NaCl. Based on the common features of proline-rich proteins (high proline content, repeated motifs, and a putative signal peptide) and their involvement in the cell wall, it is likely that the PTGRP protein is targeted to the cell wall. Its down regulation by drought could be correlated with the remodeling of the plant cell wall in response to water stress. Key words : proline-, threonine-, and glycine-rich protein, down regulation, drought, Lycopersicon chilense, tomato.
Synaptic defects ofasynaptichomozygotes in maize at the electron microscope level
Authors: Maguire M. P. , Riess R. W.
Published: May 2008

More detailed observations of the synaptonemal complex (SC) in asynaptic maize plants have been faciliated by superior silver-staining procedures. These suggest that central region components of the SC are strongly implicated as defective in asynaptic. Apparently homologous axial elements tend to follow roughly parallel courses within the nucleus at pachytene, in some short segments apparently synapsed and in others at wider separation than normal synapsis yet close enough to allow observation of thin central element segments and also occasional thin transverse element-type structures. This kind of transverse filament may be weakened and severely stretched yet associated with both axial elements. Small nodules, similar to recombination nodules, appear at corresponding positions in widely separated axial elements. Key words : synaptonemal complex, central element, transverse filament, recombination nodule.
Meiotic synapsis of the Allium porrum B chromosome: evidence for a derived isochromosome origin
Authors: Khazanehdari K. A. , Jones G. H.
Published: May 2008

Ultrastructural analysis of B chromosome synapsis in surface-spread (2B) pollen mother cells of the leek, Allium porrum, has clarified their structural organization and shed new light on their origin. In pachytene cells containing two B chromosomes, these chromosomes either formed a pair of univalents showing foldback hairpin loops or synapsed together to form bivalents of several different types. The synaptic configurations of univalents and bivalents indicate that these B chromosomes have a basically isochromosome organization, but this is modified by a slight centric shift giving an arm ratio of 1.1:1. This analysis adds to the growing number of B chromosomes that have been shown to be isochromosomes or isochromosome derivatives. Key words : Allium porrum, B chromosomes, synapsis, synaptonemal complex, isochromosome.
Development of a SCAR marker linked to the I gene in common bean
Authors: Melotto M. , Afanador L. , Kelly J. D.
Published: May 2008

Two 24-mer SCAR primers (SW13) were developed from a previously identified 10-mer RAPD primer (OW13690) linked to the I gene, which conditions resistance to bean common mosaic virus (BCMV) in common bean. Linkage between SW13 and the I gene was tested in three F2 populations segregating for both SW13 and the I gene: N84004/Michelite (1.0 ± 0.7 cM), Seafarer/UI-114 (1.3 ± 0.8 cM), and G91201/Alpine (5.0 ± 2.2 cM). SW13 proved to be more specific and reproducible than the OW13690 RAPD marker. Using different heat-stable DNA polymerases, SW13 amplified a single 690-bp fragment linked to the I gene that more consistently permitted the identification of resistant plants. In addition, the presence of the I gene was detected using SW13 in genotypes originating from different gene pools of Phaseolus vulgaris L., indicating a broad utility of this marker for bean breeding programs. Key words : Phaseolus vulgaris, SCAR, RAPD, BCMV.
Localization of rDNA genes in European eel (Anguilla anguilla) by FISH
Authors: Viñas A. , Gómez C. , Martínez P. , Sánchez L.
Published: May 2008

A probe containing most of the transcription unit of the major ribosomal genes of Xenopus laevis has been used to localize the rDNA cluster of European eel (Anguilla anguilla) by fluorescence in situ hybridization (FISH). Only one NOR-bearing chromosome pair has been found. The results obtained with this technique confirm the size polymorphism of the NOR revealed previously by other classical cytogenetic techniques. Key words : Anguilla anguilla, rDNA, NOR, FISH, heteromorphism.
Stem cell factor and c-kit are involved in hepatic recovery after acetaminophen-induced liver injury in mice
Authors: Hu Bin , Colletti Lisa M.
Published: May 2008

Stem cell factor (SCF) and its receptor c-kit are important in hematopoiesis and cellular proliferation. c-kit has also been identified as a cell surface marker for progenitor cells. We have previously shown that there is a large reservoir of hepatic SCF, and this molecule plays a significant role in liver regeneration after 70% hepatectomy. In the current study, we further examined the expression of SCF and c-kit in acetaminophen (APAP)-induced liver injury in C57BL/6J mice or SCF-deficient sl-sld mice and their appropriate wild-type controls. Following APAP-induced liver injury, c-kit mRNA expression increased, with peak levels detected 48 h postinjury. Hepatic SCF mRNA levels after APAP injury were also increased, with peak levels seen 16 h post-APAP. The mortality rate in SCF-deficient mice treated with APAP was significantly higher than that of wild-type mice; furthermore, administration of exogenous SCF significantly reduced the mortality of APAP-treated wild-type mice. Bromodeoxyuridine incorporation experiments showed that SCF significantly increased hepatocyte proliferation at 48 and 72 h in APAP-treated mice. SCF inhibited APAP-induced hepatocyte apoptosis and increased Bcl-2 and Bcl-xL expression, suggesting that this decrease in hepatocyte apoptosis is mediated through Bcl-2 and Bcl-xL. In summary, SCF and c-kit expression was increased after APAP-induced liver injury. Administration of exogenous SCF reduces mortality in APAP-treated mice, increases hepatocyte proliferation, and prevents hepatocyte apoptosis induced by APAP, suggesting that these molecules are important in the liver's recovery from these injuries.
Gene therapy of Cav1.2 channel with VIP and VIP receptor agonists and antagonists: a novel approach to designing promotility and antimotility agents
Authors: Shi Xuan-Zheng , Sarna Sushil K.
Published: May 2008

Recent findings show that the enteric neurotransmitter VIP enhances gene transcription of the α1C subunit of Cav1.2 (L-type) Ca2+ channels in the primary cultures of human colonic circular smooth muscle cells and circular smooth muscle strips. In this study, we investigated whether systemic infusion of VIP in intact animals enhances the gene transcription and protein expression of these channels to accelerate colonic transit. We also investigated whether similar systemic infusions of VPAC1/2 receptor antagonist retards colonic transit by repressing the constitutive gene expression of the α1C subunit. We found that the systemic infusion of VIP for 7 days by a surgically implanted osmotic pump enhances the gene and protein expression of the α1C subunit and circular muscle contractility in the proximal and the middle rat colons, but not in the distal colon. A similar systemic infusion of VPAC1/2 receptor antagonist represses the expression of the α1C subunit and circular smooth muscle contractility in the proximal and the middle colons. The VIP infusion accelerates colonic transit and pellet defecation by rats, whereas the infusion of VPAC1/2 receptor antagonist retards colonic transit and pellet defecation. VPAC1 receptors, but not VPAC2 receptors, mediate the above gene transcription-induced promotility effects of VIP. We conclude that VIP and VPAC1 receptor agonists may serve as potential promotility agents in constipation-like conditions, whereas VPAC receptor antagonists may serve as potential antimotility agents in diarrhea-like conditions produced by enhanced motility function.
Regulation of transforming growth factor β-induced responses by protein kinase A in pancreatic acinar cells
Authors: Yang Huibin , Lee Cheong J. , Zhang Lizhi , Sans Maria Dolors , Simeone Diane M.
Published: May 2008

TGF-β is an important regulator of growth and differentiation in the pancreas and has been implicated in pancreatic tumorigenesis. We have recently demonstrated that TGF-β can activate protein kinase A (PKA) in mink lung epithelial cells (Zhang L, Duan C, Binkley C, Li G, Uhler M, Logsdon C, Simeone D. Mol Cell Biol 24: 2169–2180, 2004). In this study, we sought to determine whether TGF-β activates PKA in pancreatic acinar cells, the mechanism by which PKA is activated, and PKA's role in TGF-β-mediated growth regulatory responses. TGF-β rapidly activated PKA in pancreatic acini while having no effect on intracellular cAMP levels. Coimmunoprecipitation experiments demonstrated a physical interaction between a Smad3/Smad4 complex and the regulatory subunits of PKA. TGF-β also induced activation of the PKA-dependent transcription factor CREB. Both the specific PKA inhibitor H89 and PKI peptide significantly blocked TGF-β's ability to activate PKA and CREB. TGF-β-mediated growth inhibition and TGF-β-induced p21 and SnoN expression in pancreatic acinar cells were blocked by H89 and PKI peptide. This study demonstrates that this novel cross talk between TGF-β and PKA signaling pathways may play an important role in regulating TGF-β signaling in the pancreas.
Inhibition of tristetraprolin deadenylation by poly(A) binding protein
Authors: Rowlett Robert M. , Chrestensen Carol A. , Schroeder Melanie J. , Harp Mary G. , Pelo Jared W. , Shabanowitz Jeffery , DeRose Robert , Hunt Donald F. , Sturgill Thomas W. , Worthington Mark T.
Published: May 2008

Tristetraprolin (TTP) is the prototype for a family of RNA binding proteins that bind the tumor necrosis factor (TNF) messenger RNA AU-rich element (ARE), causing deadenylation of the TNF poly(A) tail, RNA decay, and silencing of TNF protein production. Using mass spectrometry sequencing we identified poly(A) binding proteins-1 and -4 (PABP1 and PABP4) in high abundance and good protein coverage from TTP immunoprecipitates. PABP1 significantly enhanced TNF ARE binding by RNA EMSA and prevented TTP-initiated deadenylation in an in vitro macrophage assay of TNF poly(A) stability. Neomycin inhibited TTP-promoted deadenylation at concentrations shown to inhibit the deadenylases poly(A) ribonuclease and CCR4. Stably transfected RAW264.7 macrophages overexpressing PABP1 do not oversecrete TNF; instead they upregulate TTP protein without increasing TNF protein production. The PABP1 inhibition of deadenylation initiated by TTP does not require the poly(A) binding regions in RRM1 and RRM2, suggesting a more complicated interaction than simple masking of the poly(A) tail from a 3′-exonuclease. Like TTP, PABP1 is a substrate for p38 MAP kinase. Finally, PABP1 stabilizes cotransfected TTP in 293T cells and prevents the decrease in TTP levels seen with p38 MAP kinase inhibition. These findings suggest several levels of functional antagonism between TTP and PABP1 that have implications for regulation of unstable mRNAs like TNF.