Identification of an alien chromosome in the common wheat line multi 6R

The chromosome of Agropyron intermedium (Host) Beauv. substituting chromosome 6D has been identified in the karyotype of the Triticum aestivum L. line Multi 6R with the use of C-banding. The alien chromosome, temporarily designated 6Ag1, contains gene(s) of the resistance to the Saratov population of Puccinia recondita Rob. ex. Desm. f. tritici. It has been demonstrated that the resistance gene(s) is(are) highly efficient and that chromosome 6Ag1 is preferably transferred through gametes.     

The use of artificial neural networks for Aegilops species identification based on analysis of D genomes

The possibilities of the use of artificial neural networks (ANNs) for identification of some polyploid species of genus Aegilops based on the idiograms of their D genomes were demonstrated.     

Vivid molecular divergence over volcanic remnants: the phylogeography of Megadromus guerinii on Banks Peninsula,New Zealand

Megadromus guerinii, an endemic carabid beetle (Carabidae), is the most common carabid throughout its restricted range on Banks Peninsula, a formation of extinct volcanoes in Canterbury, New Zealand. This study characterises the small-scale phylogeographic patterns of M. guerinii across the formerly volcanically active Banks Peninsula using mitochondrial and ribosomal genes. Between the eastern and western areas of the peninsula, the mitochondrial, but not nuclear, DNA has a well-defined geographic distribution. Specifically, mitochondrial cytochrome c oxidase subunit I (CO1) identifies two distinct groups (> 6% divergence between eastern and western beetles) while ribosomal genes show no discernible pattern. Whether such a pattern represents male-biased dispersal, Wolbachia infection, a recent range expansion of a divergent lineage, or a deeper historic separation is explored. There is potential that male-biased dispersal could have occurred. Wolbachia infection was not detected. We conclude that historical processes have likely separated taxa in the eastern and western peninsula.     

Traction force on a kinetochore at metaphase acts as a linear function of kinetochore fiber length

We are investigating the relation between the force pulling a kinetochore poleward and the length of the corresponding kinetochore fiber. It was recognized by Ostergren in 1950 (Hereditas 36:1-19) that the metaphase position of a chromosome could be achieved by a balance of traction forces were proportional to the distance from kinetochore to pole. For the typical chromosome (i.e., a meiotic bivalent or mitotic chromosome) with a single kinetochore fiber extending to each pole, the resultant force (RF) would equal zero when the chromosome lay at the midpoint between the two poles. For special chromosomes that have unequal numbers of kinetochore fibers extending towards opposite poles. For special chromosomes that have unequal numbers of kinetochore fibers extending towards opposite poles. For special chromosomes that have unequal numbers of kinetochore fibers extending towards opposite poles, Ostergren’s proposal suggests that RF = 0 when the chromosome is shifted closer to the pole toward which the greater number of kinetochore fibers are pulling. We have measured the force-length relationship in living spindles by analyzing the metaphase positions of experimentally generated multivalent chromosomes having three or four kinetochore fibers. Multivalent chromosomes of varied configurations were generated by γ-irradiation of nymphs of the grasshopper melanoplus differentialis, and their behavior was analyzed in living first meiotic spermocytes. The lengths of kinetochore fibers were determined from time-lapse photographs by measuring the kinetochore-to-pole distances for fully congressed chromosomes just before the onset of anaphase. In our analysis, force (F) along a single kinetochore fiber is expressed by: F = kL(exp), where k is a length-independent proportionality constant, L represents the kinetochore fiber length, and exp is an unknown exponent. The RF on a chromosome is then given by: RF = σk(i)L(i)(exp), where kinetochore fiber lengths in opposite half- spindles are given opposite sign. If forces on a metaphase chromosome are at equilibrium (RF = 0), then for asymmetrical orientations of multivalents we can measure the individual kinetochore fiber lengths (L(i)) and solve for the exponent that yields a resultant force of zero. The value of the exponent relates how the magnitude of force along a kinetochore fiber varies with its length. For six trivalents and one naturally occurring quadrivalent we calculated an average value of exp = 1.06 +/- 0.18. This result is consistent with Ostergren’s hypothesis and indicates that the magnitude of poleward traction force along a kinetochore fiber is directly proportional to the length of the fiber. Our finding suggests that the balance of forces along a kinetochore fiber may be a major factor regulating the extent of kinetochore microtubule assembly.     

Intraspecific karyotype divergence inTriticum araraticum (Poaceae)

Karyotypes of 185 accessions ofTriticum araraticum Jakubz. (2n = 28 = 4x = A^tA^tGG) from Iraq, Iran, Turkey, and Transcaucasia were analyzed using C-banding technique. All accessions showed a certain degree of C-banding polymorphism and further karyotypic diversity was generated by structural rearrangements, mainly translocations. Eighty-one accessions had the normal karyotype similar to that ofT. timopheevii (cultivation), i.e., they showed C-banding polymorphism but no chromosomal rearrangements based on the resolving power of the C-banding technique. One-hundred four accessions showed 34 karyotypic variants, 31 had reciprocal translocations with the breakpoints in the centromeric regions of chromosomes. Three showed reciprocal translocations with the breakpoints in intercalary regions of chromosomes. A paracentric inversion for 7A^t chromosome was observed in some accessions. The rearranged karyotypes differed from the normal by one translocation in 21 variants, by two in 9 variants, by three in 1 variant, and by four in 2 variants of karyotypes. Translocations occurred more frequenty in the chromosomes of G-genome than of A^t-genome. Individual chromosomes differed in the frequencies of their involvement in translocations. Each geographical region contained a unique spectrum of translocations. Karyotypic diversity was the highest in Iraq followed by Transcaucasia and Turkey. Iran showed little karyotypic variation. Based on karyotypic analysis, Iraq should be considered as a centre of origin and primary centre of diversity ofT. araraticum.     

Comparative analysis of <Emphasis Type="Italic">Agropyron intermedium</Emphasis> (Host) Beauv 6Ag<Superscript>i</Superscript> and 6Ag<Superscript>i</Superscript>2 chromosomes in bread wheat cultivars and lines with wheat–wheatgrass substitutions

A comparative study of wheat–wheatgrass substituted cultivars and lines resistant to leaf rust developed by the Agricultural Research Institute for Southeast Regions (Multi 6R, Belyanka, Favorit, Voevoda, Lebedushka) and Samara Agricultural Research Institute (Tulaikovskaya 5, Tulaikovskaya 10, Tulaikovskaya 100, Tulaikovskaya Zolotistaya) breeding was conducted. A complex analysis using molecular cytogenetic (C-differential banding, fluorescent (FISH) and genomic (GISH) in situ hybridization), molecular (PLUG markers), and biochemical (electrophoretic analysis of gliadins) markers demonstrated that they have a substitition of wheat chromosome 6D by the chromosomes 6Agⁱ and 6Agⁱ2 belonging to the J(=E) Agropyron intermedium (Host) Beauv (=Thinopyrum intermedium (Host) Barkworth & D.R. Dewey) subgenome. In spite of the fact that the chromosomes 6Agⁱ and 6Agⁱ2 differ in the C-banding pattern and demonstrated minor differences in the blocks of gliadin components, they had the identical pattern of pSc119.2 and pAs1 probe distribution and conjugated between themselves with insignificant disturbance. Thus, it was demonstrated that 6Agi and 6Agⁱ2 are homologous chromosomes; however, the question about allelism of their leaf rust resistance genes between themselves requires special studies. Nevertheless, using STS and SCAR markers and taking into account the type of reaction to Puccinia triticina, their non-allelism to the Lr9, Lr19, Lr24, Lr29, Lr38, and Lr47 genes was established. It was revealed that the 6Agⁱ and 6Agⁱ2 chromosomes have a different level of transmission in hybrid F₂ populations depending on the hybrid combination gene background.     

Genome differentiation in Aegilops. 4. Evolution of the U-genome cluster

Phylogenetic relationships of polyploid Aegilops species sharing the U-genome were investigated by analyzing heterochromatin banding patterns of their somatic metaphase chromosomes as revealed by C-banding and fluorescence in situ hybridization (FISH) with the heterochromatin-limited repetitive DNA probes pSc119, pAs1, as well as the distribution of NOR and 5S DNA loci revealed by pTa71 (18S-26S rDNA), and pTa794 (5S rDNA) probes. Seven tetraploid (Ae. triuncialis, Ae. peregrina, Ae. kotschyi, Ae. geniculata, Ae. biuncialis, Ae. columnaris, and 4x Ae. neglecta) and one hexaploid (6x Ae. neglecta) Aegilops species of the U-genome cluster were studied. The U^t and C^t chromosomes of 4x Ae. triuncialis (U^tC^t) were similar to the diploid donors Ae. umbellulata (U) and Ae. caudata (C). However, the size of the NOR locus on chromosome 5U^t was reduced. Karyotypic analyses confirmed that 4x Ae. peregrina (S^pU^p) was derived from a hybridization of the diploid species Ae. umbellulata with Ae. longissima, whereas Ae. umbellulata and Ae. sharonensis (or an immediate precursor) were the diploid progenitor species of Ae. kotschyi (S^kU^k). In both 4x species, the NORs on S-genome chromosomes were inactivated and were accompanied with a decrease or loss of rDNA sequences. Karyotypes of the tetraploid species, Ae. geniculata (U^gM^g) and Ae. biuncialis (U^bM^b) differed from each other and from the putative diploid progenitors Ae. umbellulata and Ae. comosa indicating that various types of chromosomal alterations occurred during speciation. Inactivation of major NORs on the M-genome chromosomes, redistribution of 5S rDNA sites, and loss of some minor 18S-26S rDNA loci were observed in Ae. geniculata and Ae. biuncialis. Significant differences in the total amount and distribution of heterochromatin, the number and location of 5S and 18S-26S rDNA loci observed between Ae. columnaris (U^cX^c)/4x Ae. neglecta (UⁿXⁿ) and Ae. geniculata/Ae. biuncialis indicate that these species have different origins. Similarities in C-banding and FISH patterns of most Ae. columnaris and 4x Ae. neglecta chromosomes suggest that they were probably derived from a common ancestor, whereas distinct differences of three chromosome pairs may indicate that the divergence of these species was probably associated with chromosomal rearrangements and/or introgressive hybridization. Ae. umbellulata contributed the U genome, however, the source of their second genomes remains unknown. The formation of 6x Ae. neglecta (UⁿXⁿNⁿ) was not associated with large modifications of the parental genomes.     

Genome: Origins and evolution of the term

The appearance of a new scientific term is a significant event in the human cognitive process and the result of the realization of the separateness of an object or a phenomenon. Our article concentrates on the origins of basic genetic terms, such as genetics, gene, genotype, genome, gene pool, and genomics. We propose using the term karyogenomics for the special direction of genomics related to the study of the organization and evolution of eukaryotic genomes by means of modern chromosome analysis, as well as by full genome sequencing.     

Construction and evaluation of multisite recombinatorial (Gateway) cloning vectors for Gram-positive bacteria

Background  

The Gateway recombinatorial cloning system allows easy and rapid joining of DNA fragments. Here we report the construction and evaluation of three different Gram-positive vectors that can be used with the Multisite Gateway cloning system to rapidly produce new gene arrangements in plasmid constructs for use in a variety of Gram-positive bacteria.     

A comparative cytogenetic study of the tetraploid oat species with the A and C genomes: Avena insularis, A. magna, and A. murphyi

Differential C-banding of chromosomes and in situ hybridization with the probes pTa71 and pTa794 were used for a comparative cytogenetic study of the three tetraploid oat species with the A and C genomes: Avena insularis, A. magna, and A. murphyi. These species were similar in the structure and patterns of C-banding of several chromosomes as well as in the location of the loci 5S rRNA genes and main NOR sites; however, they differed in the number and localization of minor 45S rDNA loci as well as in the morphology and distribution of heterochromatin in some chromosomes. According to the data obtained, A. insularis is closer to A. magna, whereas A. murphyi is somewhat separated from these two species. Presumably, all the three studied species originated from the same tetraploid ancestor, and their divergence is connected with various species-specific chromosome rearrangements. The evolution of A. murphyi is likely to have occurred independently of the other two species.