Reciprocal homologous junctions generated in mouse cells

Summary We analysed pairs of reciprocal homologous junctions resulting from intermolecular conservative homologous recombination in mouse cells. The assay used did not rely on the reconstitution of a selectable gene. This permitted the introduction of multiple markers in the parental homologous sequences which in turn enabled us to compare the contribution of each parent to the reciprocal products of a given recombination event. In all recombinants analysed we found, when comparing the reciprocal junctions, a middle segment originating from only one parent. This segment of uniparental origin occurred randomly throughout the region of homology and could extend over a thousand base pairs. These results are consistent with a gap repair process like the one proposed for homologous recombination in yeast. However, introducing a double-strand break in the region of homology did not enhance but rather decreased the proportion of recombinants with reciprocal homologous junctions relative to other types of recombinants.     

Evolution of crossover interference enables stable autopolyploidy by ensuring pairwise partner connections in Arabidopsis arenosa

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Fluorescence in situ hybridization with multiple repeated DNA probes applied to the analysis of wheat-rye chromosome pairing

 Fluorescence in situ hybridization (FISH) with multiple probes has been applied to meiotic chromosome spreads derived from ph1b common wheat x rye hybrid plants. The probes used included pSc74 and pSc 119.2 from rye (the latter also hybridizes on wheat, mainly B genome chromosomes), the Ae. squarrosa pAs1 probe, which hybridizes almost exclusively on D genome chromosomes, and wheat rDNA probes pTa71 and pTa794. Simultaneous and sequential FISH with a two-by-two combination of these probes allowed unequivocal identification of all of the rye (R) and most of the wheat (W) chromosomes, either unpaired or involved in pairing. Thus not only could wheat-wheat and wheat-rye associations be easily discriminated, which was already feasible by the sole use of the rye-specific pSc74 probe, but the individual pairing partners could also be identified. Of the wheat-rye pairing observed, which averaged from about 7% to 11% of the total pairing detected in six hybrid plants of the same cross combination, most involved B genome chromosomes (about 70%), and to a much lesser degree, those of the D (almost 17%) and A (14%) genomes. Rye arms 1RL and 5RL showed the highest pairing frequency (over 30%), followed by 2RL (11%) and 4RL (about 8%), with much lower values for all the other arms. 2RS and 5RS were never observed to pair in the sample analysed. Chromosome arms 1RL, 1RS, 2RL, 3RS, 4RS and 6RS were observed to be exclusively bound to wheat chromosomes of the same homoeologous group. The opposite was true for 4RL (paired with 6BS and 7BS) and 6RL (paired with 7BL). 5RL, on the other hand, paired with 4WL arms or segments of them in more than 80% of the cases and with 5WL in the remaining ones. Additional cases of pairing involving wheat chromosomes belonging to more than one homoeologous group occurred with 3RL, 7RS and 7RL. These results, while adding support to previous evidence about the existence of several translocations in the rye genome relative to that of wheat, show that FISH with multiple probes is an efficient method by which to study fundamental aspects of chromosome behaviour at meiosis, such as interspecific pairing. The type of knowledge attainable from this approach is expected to have a significant impact on both theoretical and applied research concerning wheat and related Triticeae. Received: 21 February 1996 / Accepted: 12 July 1996     

Are rice chromosomes components of a holocentric chromosome ancestor?

Comparative genomics reveals that cereal genomes are composed of similar genomic building blocks (linkage blocks). By stacking these blocks in a unique order, it is possible to construct a single ancestral chromosome which can be cleaved to give the basic structure of the 56 different chromosomes found in wheat, rice, maize, sorghum, millet and sugarcane. The borders of linkage blocks are defined by cereal centromeric and telomeric sites. However, a number of studies have shown that telomeric heterochromatin has neocentromeric activity, implying that linkage blocks are in fact defined by centromeric-like sites with conserved sequences. The structure of the ancestral cereal genome thus resembles a holocentric chromosome, which is the chromosome structure shared by the closest relatives of the Gramineae, the Cypericeae and Juncaceae.     

日本血吸虫单性感染雄虫和双性感染雄虫差异表达蛋白的筛选与鉴定

采用双向凝胶电泳和质谱技术对日本血吸虫单性感染雄虫和双性感染雄虫蛋白质表达谱进行分析，并在mRNA水平进行验证；观察差异表达SJCHGC蛋白重组真核表达质粒pEGFP-C1/SJCHGC在COS-7细胞中的表达和亚细胞定位，并分析其表达产物的抗原性. 成功鉴定了9个日本血吸虫雌雄合抱差异表达蛋白，其中在日本血吸虫雄虫合抱前表达上调的蛋白质有6个；而有3个蛋白质在日本血吸虫雄虫合抱后表达明显上调. 大多数差异蛋白功能涉及血吸虫的生长发育、生殖、营养、运动、信号传递等过程. 重组质粒pEGFP-C1/SJCHGC 融合基因真核表达载体在真核细胞COS-7中获得了表达,可用荧光显微镜直接观察其表达情况及亚细胞定位,细胞所表达的融合蛋白具有血吸虫抗原性. 研究结果为揭示日本血吸虫雌雄合抱机制、研制抗血吸虫雌雄合抱疫苗提供了理论依据.     

Sequence data: Magnitude and implications of some ambiguities

Summary Glx and Asx ambiguities introduce errors into evolutionary conclusions drawn from the sequences of incompletely analyzed proteins. These errors are of sufficient magnitude to invalidate some of these conclusions.     

The stochastic model and deviations from randomness in eukaryotictRNAs: Comparison with the PAM approach

Summary The stochastic model of molecular evolution was used to makea priori predictions for the total number of one-step nucleotide changes required to account for a given observed number of nucleotide substitutions between two homologous nucleic acids. The experimental deviations from randomness found for eukaryotic transfer RNAs and summarized by Dayhoff and McLaughlin (1972) are shown to affect only slightly the quantitative predictions of the model. This is true for both short and long periods of evolutionary divergence. The model can thus be used with some confidence for quantitatively correcting the branch lengths of phylogenetic trees derived from either nucleic acid sequence or hybridization data.     

Characterization of Genome and Chromosomes in Octoploid Wheat wheatgrass Amphiploid Zhong 2 Using Fluorescence in situ Hybridization and Chromosome Pairing Analysis

Genomic constitution of octoploid wheat-wheatgrass amphiploid Zhong 2 was analyzed by chromosome pairing and fluorescence in sim hybridization techniques. The results indicated that the octoploid wheatwheatgrass chromosomes in Zhong 2 were derived from the distant homologous genomes of wheatgrass ( Agropyron intermedium (Host) P.B. = Elytrigia intermedia (Host) Nevski = Thinotopyrum intermedium (Host) Barkworth and Dewey, and thew distant homologous genomes were not from the E geaome of T. elongatum 2x. Zhong 2 contained 12 wheatgrass chromosomes in which a pair of chromosomes was involved in translocation between wheatgrass and wheat chromosomes.     

Morphology,fertility and cytogenetics of intergeneric hybrid between Roegneria kamoji Ohwi and Dasypyrum villosum (L.) Candargy (Poaceae: Triticeae)

The intergeneric hybrids between Roegneria kamoji Ohwi and Dasypyrum villosum (L.)Candargy were successfully obtained by means of embryo culture in vitro. Studies on morphology, fertility and chromosome pairing behavior in meiosis of the parents and their hybrid F_l were carried out in the present work. The results showed that: (1) there were ob vious morphological differences between R. kamoji and D. villosum, and spikes of F_l plants were morphologically intermediate between the two parental species; (2) the seed set of the cross was 11.63%; the hybrid plant was infertile, which indicated that strong repro ductive isolation existed between the parents and R. kamoji and D. villosum were inde pendent biological species; (3) The somatic chromosome number in root-tips of F_l hybrids was 28. Chromosome pairing at MI of PMCs in F_l hybrids was quite low. The meiotic con figuration was 26.72 Ⅰ + 0.62 Ⅱ + 0.02 Ⅲ, which indicated that very low homoeology was detected between the St, H, Y genomes of R. kamoji and the V genome of D. villo- sum, and the relationship between the parental species was remote.     

A computational study of dsDNA pairs and vibrational resonance in separating water

This article investigates the relationship between molecular sequence and dependent interacting behavior of molecular segment pairs and secondly, sequence dependent, vibrational resonance in surrounding normal saline, protein-free water. The development of a molecular model to explore these systems phenomena, the results of several nanoscale molecular dynamics simulations, and analysis of behavior of interacting ΦX174 double-stranded DNA segment pair models in various configurations are presented. Fourier analysis revealed intriguing vibration frequencies within the solvent plane between the segments, while subsequent frequency domain transformation of the time domain waveforms revealed statistically significant resonating harmonic signals in the THz range.

Electronic supplementary material

The online version of this article (doi:10.1007/s11693-014-9157-3) contains supplementary material, which is available to authorized users.