Thinopyrum distichum addition lines: production,morphological and cytological characterisation of 11 disomic addition lines and stable addition-substitution line

Plants of the partial amphiploid Inia 66/Thinopyrum distichum (2n = 70)//Inia 66 (2n = 56) were used as male parents in crosses with the monosomic series in the common wheat cultivar Inia 66. The genome and homoeologous group of the monosomic used in the cross affected the distribution of chromosome number of the progeny plants in the F₂ and F₄. Meiosis in the pollen mother cells of the B₁F₇ partial amphiploids was not stable, and not different from that of the B₁F₁ in which univalents and multivalents were observed. Disomic addition lines were selected on the basis of morphology and meiotic stability in the F₂, F₄ and F₅. Eleven of the fourteen possible wheat-Th. distichum disomic addition lines were identified using chromosome C-band pattern, as well as size and arm ratio, as genetic markers. Addition of T. distichum chromosome J^dllproduced a phenotype indicating homoeology with wheat group-2 chromosomes. Clear indications of homoeology based on morphological characteristics were not obtained in any of the other addition lines, probably due to the mixed homoeology of the Th. distichum chromosomes relative to wheat. The addition lines were all susceptible to leaf rust, unlike the germplasm-line Indis which carries a leaf rust resistance gene on a translocation segment derived from Th. distichum. Instability of meiotic pairing was observed in all addition lines. The stability, or not, of progeny chromosome counts did not reflect the level of chromosome pairing instability in the parental plants. SDS-PAGE for gliadin-type seed proteins revealed two addition lines which expressed seed storage proteins uncommon to Inia 66 but typical of Th. distichum.     

Establishment of a plant regeneration system for wheatgrasses (Thinopyrum,Agropyron and Pascopyrum)

Wheatgrasses (Thinopyrum, Agropyron and Pascopyrum spp.) are a ubiquitous group of cool-season grasses used throughout much of the semiarid temperate world. In order to explore the potential of biotechnology to accelerate conventional breeding efforts, we developed an efficient plant regeneration system for different wheatgrass species: tall wheatgrass [Thinopyrum ponticum (Podp.) Liu and Wang], intermediate and pubescent wheatgrass [Thinopyrum intermedium (Host) Barkw. and D.R. Dewey], crested wheatgrass [Agropyron cristatum (L.) Gaertner], and western wheatgrass [Pascopyrum smithii (Rydb.) Löve]. Embryogenic callus was induced from mature and immature embryos and immature inflorescence with an induction frequency in the range of 0.5–8.3% for the different wheatgrass species tested. Individual embryogenic calluses were then used to establish single genotype-derived suspension cultures. Efficient plant regeneration was achieved from the established em-bryogenic suspensions with regeneration frequencies in the range of 20–65% for tall wheatgrass, 21–40% for intermediate and pubescent wheatgrasses, 32–51% for crested wheatgrass, and 25–48% for western wheatgrass. The cell suspension-derived wheatgrass plants were fertile and phenotypically normal in the field. The efficient plant regeneration system provides a solid basis for genetic transformation of wheatgrasses.     

C-band morphology of T(8;9)/8;9 in Blattella germanica

Summary Centromere position and each arm of the T(8;9)/8;9 quadrivalent at late pachytene can be recognized by C-banding. The chromosome 9 breakpoint lies immediately adjacent to the centromeric C-band; that of 8, in the general region of the centromere but the relationship to centromeric bands was not determined since the latter stain very faintly. Chromosome 9 differs from no. 8 in the presence of a complex series of intercalary bands, heavy centromeric bands and, overall, a larger amount of C-band material. Possible implications of these differences with respect to chromosome breakability and the nature and distribution of mutant loci are noted. Earlier identification of adjacent-1 and adjacent-2 metaphase I ring orientations, made on the basis of orientation pattern, was confirmed.     

Thinopyrum ponticum and Th. intermedium:the promising source of resistance to fungal and viral diseases of wheat

Thinopyrum ponticum and Th. intermedium provide superior resistance against various diseases in wheat （Ttricum aestivum）. Because of their readily crossing with wheat, many genes for disease resistance have been introduced from the wheatgrasses into wheat. Genes for resistance to leaf rust, stem rust, powdery mildew, Barley yellow dwarf virus, Wheat streak mosaic virus, and its vector, the wheat curl mite, have been transferred into wheat by producing chromosome translocations. These genes offer an opportunity to improve resistance of wheat to the diseases; some of them have been extensively used in protecting wheat from damage of the diseases. Moreover, new resistance to diseases is continuously detected in the progenies of wheat-Thinopyrum derivatives. The present article summaries characterization and application of the genes for fungal and viral disease-resistance derived from Th. ponticum and Th. intermedium.     

提莫菲维小麦C—带和N—带异染色质的比较研究

利用C-带和N-带分别及连续处理技术对提莫菲维小麦(Triticum timopheevi Zhuk.)的染色体带型及异染色质的类型与分布进行比较分析。结果表明,提莫菲维小麦的4A染色体以及G-染色体组带型丰富,并具有明显的端带,其异染色质是多样化的。4G和6G为随体染色体,随体显带明显。在提莫菲维小麦的染色体中异染色质类型有:(1)只有C~ N~ 型(4A、4G、6G和7G染色体);(2)只有C~ N~-型(1A、5A、6A和7A染色体);(3)C~ N~ 和C~ N~-型(2A、3A、1G、2G、3G和5G染色体)。在C-带和N-带连续处理中,N-带异染色质的消失部位在1G、2G、3G和5G染色体的端部,3A染色体的着丝点附近以及染色体1A、2A、5A、6A和7A的着丝点附近及端部。本文还讨论了C-带和N-带异染色质的异同以及端部异染色质在G染色体组进化中的可能作用。     

Whole-genome chromosome distribution during nuclear fragmentation of giant trophoblast cells of Microtus rossiaemeridionalis studied with the use of gonosomal chromatin arrangement

Gonosomal chromatin bodies (GCBs), i.e. blocks of condensed chromatin consisting of heterochromatized region of the sex chromosomes of the field vole M. rossiaemeridionalis, were used as a natural interphase chromosome marker in order to clarify the regularities of GCB rearrangement during nuclear fragmentation of secondary giant trophoblast cells (SGTCs) at the end of their differentiation. Cytophotometrical measurements of DNA content in the nuclei, nuclear fragments and simultaneously in the GCBs were made in the secondary giant SGTCs of field vole M. rossiaemeridionalis. In most cases 1 to 2 GCBs get into the nuclear fragments at different ploidy levels. In the nuclear fragments, GCB DNA content decreased mostly proportionally to DNA content in the whole fragments corresponding to 2c, 4c and 8c. The data obtained demonstrate a regular whole-genome chromosome distribution into nuclear fragments. A possible mechanism of nuclear fragmentation that largely ensures a balanced genome in nuclear fragments is discussed.     

C-band distribution,DNA content and base composition inAdoxa moschatellina (Adoxaceae), a plant with cold-sensitive chromosome segments

The chromosomes ofAdoxa moschatellina (2n = 36, paleo-4x) contain mostly terminal, occasionally intercalary, negatively heteropycnotic cold-induced regions which correspond to all major C-bands including the satellites, as revealed by sequential analysis. Positively C-stained are also centromeres, the dotlike arms of the 7 telocentric chromosome pairs, and some very narrow intercalary bands; their cold-sensitivity is hardly traceable. There exists a fraction of condensed interphase chromatin, at least after chilling, which is virtually not C-banded (possibly condensed euchromatin).The DNA amount is 14.3 pg (1 C). The heterochromatin content is 13.0%. The thermal melting profile (Tm corresponding to 38.6% GC) does not reveal a particular AT- or GC-rich fraction. Significantly, the heterochromatin respond to the Hy-banding procedure is neutral.The distribution of cold-sensitive regions in plants was analysed with the arm-frame method: Intercalary positions, clearly, are not especially favoured regions. The obvious deficiency at centromeric positions may depend on the action of natural selection against mechanically labile centromeric regions.Dedicated to Univ.-Prof. Dr.Lothar Geitler on the occasion of his 80th birthday.     

Interplay between genome organization and epigenomic alterations of pericentromeric DNA in cancer

In eukaryotic genome biology, the genomic organization inside the three-dimensional(3 D) nucleus is highly complex, and whether this organization governs gene expression is poorly understood. Nuclear lamina(NL)is a filamentous meshwork of proteins present at the lining of inner nuclear membrane that serves as an anchoring platform for genome organization. Large chromatin domains termed as lamina-associated domains(LADs), play a major role in silencing genes at the nuclear periphery. The interaction of the NL and genome is dynamic and stochastic. Furthermore, many genes change their positions during developmental processes or under disease conditions such as cancer, to activate certain sorts of genes and/or silence others. Pericentromeric heterochromatin(PCH) is mostly in the silenced region within the genome, which localizes at the nuclear periphery. Studies show that several genes located at the PCH are aberrantly expressed in cancer. The interesting question is that despite being localized in the pericentromeric region,how these genes still manage to overcome pericentromeric repression. Although epigenetic mechanisms control the expression of the pericentromeric region, recent studies about genome organization and genome-nuclear lamina interaction have shed light on a new aspect of pericentromeric gene regulation through a complex and coordinated interplay between epigenomic remodeling and genomic organization in cancer.     

Tissue-culture-facilitated production of aneupolyhaploid Thinopyrum ponticum and amphidiploid Hordeum violaceum x H. bogdanii and their uses in phylogenetic studies

Summary An aneupolyhaploid (2n = 36) of the decaploid Thinopyrum ponticum and an amphidiploid (2n = 28) of Hordeum violaceum x Hordeum bogdanii were produced through anther and inflorescence culture, respectively. Meiotic associations in pollen mother cells at metaphase I of these plants were analyzed. The aneupolyhaploid arose by direct embryogenesis from a microspore without passing through a callus phase. The mean pairing frequencies of 2.67 univalents ⁺ 0.54 rod bivalents ⁺ 8.85 ring bivalents ⁺ 2.75 trivalents ⁺ 0.17 chain quadrivalents ⁺ 0.56 ring quadrivalents ⁺ 0.65 pentavalents in the aneupolyhaploid (2n = 36) best fit the 221 model. However, the frequent multivalents (up to five trivalents, or three quadrivalents, or four pentavalents in a cell) indicated that decaploid T. ponticum has five sets of closely related genomes representable by the genome formula J₁ J₁ J₁ J₂ J₂. Colchicine treatment of inflorescence-derived H. violaceum x H. bogdanii regenerants greatly enhanced the rate of chromosome doubling, and completely doubled regenerants could be isolated. The H. violaceum x H. bogdanii amphidiploid had a mean pairing pattern of 12.53 univalents ⁺ 5.57 rod bivalents ⁺ 1.97 ring bivalents ⁺ 0.07 trivalents ⁺ 0.03 hexavalents, indicating the presence of desynaptic gene(s) in the original diploiid hybrid. Therefore, the pairing frequency in that diploid hybrid was an under-estimate of chromosome homology between the parental genomes, and additional diploid hybrids are needed to assess the genome homology between H. violaceum and H. bogdanii. These two contrasting experiments demonstrated that tissue culture techniques are useful in altering the ploidy level to produce plant materials suitable for genome analysis and phylogenetic studies.Cooperative investigation of the USDA-ARS, Forage and Range Research Laboratory, Logan, UT 84322-6300, and the Utah Agricultural Experiment Station, Utah State University, Logan, UT 84322-4810. Approved as journal paper No. 3991     

Genome size variation and C-band polymorphism inAlstroemeria aurea, A. ligtu andA. magnifica (Alstroemeriaceae)

Among a total of 43 accessions ofAlstroemeria aurea, A. ligtu andA. magnifica nuclear DNA amounts (2C-values) showed significant intraspecific variation, 1.09, 1.21 and 1.15 fold, respectively, when determined through flow cytometric measurements of fluorescence of propidium iodide (PI) stained nuclei. After staining with another fluorochrome, 4,6-diamidino-2-phenylindole (DAPI), an intraspecific variation of 1.10, 1.11 and 1.12 fold, respectively, was found. C-band polymorphisms were present among and within the accessions of all three species. In some cases only very small differences in C-banding pattern were observed. In other cases, however, differences were more prominent. Besides C-band polymorphism, there were also instances of chromosome length polymorphism, which concerned the total chromosome complement or single chromosomes. The variation in nuclear DNA amount inA. aurea andA. ligtu was more or less continuous, except for one accession ofA. ligtu subsp.simsii. Artificial selection and possibly introgression of chromosomes from other species may have moulded the karyotypes of some of the accessions ofA. aurea, a species that has been under cultivation for more than 160 years. The variation as observed inA. magnifica subsp.magnifica was discontinuous and could be due to a broad species concept.     

Inhibition of Atm and/or Atr disrupts gene silencing on the inactive X chromosome

ATM and ATR are well documented for their roles in maintaining the integrity of genomic DNA by responding to DNA damage and preparing the cell for repair. Since ATM and ATR have been reported to exist in complexes with histone deacetylases, we asked whether Atm and Atr might also uphold gene silencing by heterochromatin. We show that the Atm/Atr inhibitor 2-aminopurine causes the inactive X chromosome to accumulate abnormal chromatin and undergo unwanted gene reactivation. We provide evidence that this gene expression from the inactive X chromosome is not a byproduct of the accumulation of DNA breaks. Individually inhibiting Atm and Atr by either small interfering RNA or the expression of dominant-negative ATM and ATR constructs also compromised X-inactivation. Atm and Atr, therefore, not only function in responding to DNA damage but perhaps also are involved in gene silencing via the maintenance of heterochromatin.     

Identification and chromosomal distribution of DNA sequence segments conserved since divergence of Escherichia coli and Bacillus subtilis

DNA sequence segments conserved since divergence of Escherichia coli and Bacillus subtilis were identified, using the GenBank sequence database. Chromosomal locations of the conserved segments were compared between the two bacteria, and the following three features were observed. (1) Although the two genomes are nearly identical in size, chromosomal arrangements of the conserved segments are considerably different from each other. (2) In many cases, chromosomal locations of a conserved segment in the two species have deviated from each other by a multiple of 60°. (3) There are many instances in which a contiguous segment in one genome is split into two or more segments located at distinct positions in the other genome, and these split segments were found to tend to lie on the E. coli or B. subtilis genome separated by distances of multiples of 60°. On the basis of these observations, genome organizations of the two bacteria were discussed in terms of genome doublings as well as random chromosomal rearrangements.     

In silico comparative analysis reveals a mosaic conservation of genes within a novel colinear region in wheat chromosome 1AS and rice chromosome 5S

Comparative RFLP mapping has revealed extensive conservation of marker order in different grass genomes. However, microcolinearity studies at the sequence level have shown rapid genome evolution and many exceptions to colinearity. Most of these studies have focused on a limited size of genomic fragment and the extent of microcolinearity over large distances or across entire genomes remains poorly characterized in grasses. Here, we have investigated the microcolinearity between the rice genome and a total of 1,500 kb from physical BAC contigs on wheat chromosome 1AS. Using ESTs mapped in wheat chromosome bins as an additional source of physical data, we have identified 27 conserved orthologous sequences between wheat chromosome 1AS and a region of 1,210 kb located on rice chromosome 5S. Our results extend the orthology described earlier between wheat chromosome group 1S and rice chromosome 5S. Microcolinearity was found to be frequently disrupted by rearrangements which must have occurred after the divergence of wheat and rice. At the Lr10 orthologous loci, microrearrangements were due to the insertion of mobile elements, but also originated from gene movement, amplification, deletion and inversion. These mechanisms of genome evolution are at the origin of the mosaic conservation observed between the orthologous regions. Finally, in silico mapping of wheat genes identified an intragenomic colinearity between fragments from rice chromosome 1L and 5S, suggesting an ancestral segmental duplication in rice.Electronic Supplementary Material Supplementary material is available in the online version of this article at     

Factors limiting the distribution ofDigitaria adscendens andEleusine indica on coastal sand dunes in Japan

Fate ofDigitaria adscendens andEleusine indica seedlings under field conditions and their responses to salt spray, drought and nutrients were experimentally investigated in order to evaluate the possible mechanisms controlling the different distributions of the two species in coastal sand dune areas. Salt spray produced no apparent positive effect on the growth or survival of both species. Seeds of each species germinated well in the field, although 80% ofE. indica seedlings died during a summer drought and surviving seedlings neither grew nor bore fruit. The mortality ofD. adscendens seedlings due to the drought was less than 10% and the survivors mostly bore fruit by the end of the growth season. No major difference in the sublethal water saturation deficit was noticed between the two species. However,D. adscendens individuals extended their roots into the deep sandy soil to a much greater extent in water-stressed conditions than in well watered conditions, whereasE. indica showed no such behavior. Additional watering in a dune environment did not help the growth ofE. indica seedlings, but additional nutrients had a markedly stimulatory effect.D. adscendens maintained its growth and fruition with much smaller amounts of nutrients thanE. indica. Soil nitrogen content at a site whereE. indica andD. adscendens were distributed sympatrically was higher than that at a site where onlyD. adscendens was present. Based on these findings, it is proposed thatE. indica seedlings are unable to become established because of their lower resistance to summer drought and the poor nutrient conditions present in a coastal rear sand dune habitat. Dedicated to Prof. emeritus Toshiro Saeki for his fruitful career in plant ecology.     

Foot morphology and distribution of Sika deer in relation to snow depth in Japan

The distribution of Sika deer (Cervus nippon) on Japanese islands is biased toward, the east where there is less snow. To explain this biased distribution in relation to snow, the foot morphology of Sika deer was measured. Hoof load was greatest in male adults (0.78 kg cm⁻²) and smallest in fawns (c 0.43 kg cm⁻²). The values were similar to those for white-tailed deer, and were smaller than those for snow-adapted species like caribou and chamois. Foreleg length wasc. 50 cm and 60 cm, and hind feet (lower half) length wasc. 40 cm and 45 cm for fawns and adult deer, respectively. Chest heights werec. 45 cm and 53 cm for fawns and adults, respectively. These figures suggest that areas where snow accumulates deeper than 50 cm are not favorable as a Sika deer habitat. The present distribution of Sika deer is clearly related to snow depth: they are mostly concentrated in the ‘preferable area’ of <50 cm of snow, some of them can live in the ‘habitable area’ of 50–100 cm of snow, and they rarely live in the ‘inhabitable area’ of >100 cm of snow.     

Geographic distribution and recombination of genomic fragments on the short arm of chromosome 2 of Arabidopsis thaliana

Abstract: Range expansion from Pleistocene refugia and anthropogenic influences contribute to the present distribution pattern of Arabidopsis thaliana. We scored a genome-wide set of CAPSs and found two markers with an east-west geographic distribution across the Eurasian range of the species. Regions around the two SNPs were sequenced in 98 accessions, including newly collected plants from Middle Asia and Western Siberia. These regions correspond to a gene (∼ 1500 bp) and a non-coding region (∼ 500 bp) 300 kbp apart on chromosome 2. Nucleotide diversities, π, of the two sequenced fragments were 0.0032 and 0.0130. The haplotypes of both sequences belonged to one of two groups: a rather uniform Asian and a more variable European haplotype group, on the basis of non-disjunct clusters of SNPs. Recombination between Asian and European haplotypes occurs where they meet. Especially in the European haplotype, many rare SNP variants representing independent mutations are scattered among the shared haplotype-specific SNPs. This agrees with previous suggestions of two large haplotype groups in A. thaliana and the post-glacial colonization of central Europe from the east and the west. A clear correlation between climatic factors and the haplotype distribution may reflect the dispersal history rather than local climate adaptation. The pattern of SNP variation within the contiguous sequences explains why only a minority of SNPs selected across the genome show evidence of this geographic pattern.     

Meiotic pairing in hybrids between tetraploid Triticale and related species: new elements concerning the chromosome constitution of tetraploid Triticale

Summary Two F5 strains of tetraploid triticale (2n= 4x=28), obtained from 6x triticaleX2 rye progenies, were crossed with diploid and tetraploid rye, some durum and bread wheats, and various 8x and 6x triticale lines. Meiosis in the different hybrid combinations was studied. The results showed that the haploid complement of these triticales consists of seven chromosomes from rye and seven chromosomes from wheat. High frequencies of PMCs showing trivalents were observed in hybrids involving the reference genotypes of wheat and triticale. These findings proved that several chromosomes from the wheat component have chromosome segments coming from two parental wheat chromosomes. The origin of these heterogeneous chromosomes probably lies in homoeologous pairing occurring at meiosis in the 6x triticaleX2x rye hybrids from which 4x triticale lines were isolated. A comparison among different hybrids combinations indicated that the involvement of D-genome chromosomes in homoeologous pairing is quite limited. In contrast, meiotic patterns in 4x triticale X 2x rye hybrids showed a quite high pairing frequency between some R chromosomes and their A and B homoeologues.     

Synthesis and cytological characterization of trigeneric hybrids involving durum wheat,Thinopyrum bessarabicum,and Lophopyrum elongatum

Summary In an attempt to transfer genes for salt tolerance and other desirable traits from the diploid wheatgrasses, Thinopyrum bessarabicum (2n=2x=14; JJ genome) and Lophopyrum elongatum (2n=2x=14; EE genome), into durum wheat cv Langdon (2n=4x=28; AABB genomes), trigeneric hybrids with the genomic constitution ABJE were synthesized and cytologically characterized. C-banding analysis of somatic chromosomes of the A, B, J, and E genomes in the same cellular environment revealed distinct banding patterns; each of the 28 chromosomes could be identified. They differed in the total amount of constitutive heterochromatin. Total surface area and C-banded area of each chromosome were calculated. The B genome was the largest in size, followed by the J, A, and E genomes, and its chromosomes were also the most heavily banded. Only 25.8% of the total chromosome complement in 10 ABJE hybrids showed association, with mean arm-pairing frequency (c) values from 0.123 to 0.180 and chiasma frequencies from 3.36 to 5.02 per cell. The overall mean pairing was 0.004 ring IV + 0.046 chain IV + 0.236 III + 0.21 ring II + 2.95 rod II + 20.771. This is total pairing between chromosomes of different genomes, possibly between A and B, A and J, A and E, B and J, B and E, and J and E, in the presence of apparently functional pairing regulator Ph1. Because chromosome pairing in the presence of Ph1 seldom occurs between A and B, or between J and E, it was inferred that pairing between the wheat chromosomes and alien chromosomes occurred. The trigeneric hybrids with two genomes of wheat and one each of Thinopyrum and Lophopyrum should be useful in the production of cytogenetic stocks to facilitate the transfer of alien genes into wheat.     

A test of neutrality and constant population size based on the mismatch distribution

Several factors including demographic changes, selection, and recombination are known to affect the distribution of the number of pairwise differences between DNA sequences. The effects of each of these forces have previously been used to estimate population parameter values using various assumptions about other factors. In this article, we use the predictions of the mismatch distribution under a standard neutral equilibrium model to design a coalescent simulation-based test and detect any deviation from this equilibrium. When reliable independent estimates are available for the intragenic recombination rate, this test can be used as a neutrality test or a population expansion test in actual studies, under reasonable assumptions.     

Root distribution and morphology of maize seedlings as affected by tillage and fertilizer placement

Suboptimal soil conditions are known to result in poor early growth of maize (Zea mays L.) in no-tillage (NT) systems in contrast with conventional tillage (CT) systems. However, most studies have generally focused on maize roots at later growth stages and/or do not give details on root morphology. In a 2-year field study at two locations (silt loam and loam soils) in the Swiss midlands, we investigated the impacts of tillage intensity, NT vs. CT, and NP-fertilizer sidebanding on the morphology, vertical and horizontal distribution, and nutrient uptake of maize roots at the V6 growth stage. The length density (RLD) and the length per diameter-class distribution (LDD) of the roots were determined from soil cores taken to a depth of 0.5 m and at distances of 0.05 and 0.15 m from both sides of the maize row. The temperature of the topsoil was lower, and the bulk density and penetration resistance were greater in the topsoil of NT compared with CT. The growth and the development of the shoot were slower in NT. RLD was greater and the mean root diameter smaller in CT than in NT, while the vertical and horizontal distribution of roots did not differ between CT and NT. RLD increased in the zone enriched by the sidebanded fertilizer, independent of the tillage system, but LDD did not change. The poorer growth of the roots and shoots of maize seedlings was presumably caused by the lower topsoil temperature in NT rather than by mechanical impedance. The placement of a starter fertilizer at planting under NT is emphasized.