Investigation of a preferentially transmitted Aegilops sharonensis chromosome in wheat

Summary An attempt to produce a set of addition lines of Aegilops sharonensis to the wheat variety Chinese Spring produced only one addition line. This was due to preferential transmission of one chromosome from Ae. sharonensis. This chromosome was studied in detail by established cytological methods of chromosome observation and by the newer techniques of C-banding and in situ hybridization of a cloned DNA sequence. The chromosome was found to be partially homologous to an Ae. sharonensis chromosome of similar behaviour in another wheat addition line. The incomplete homology of the two Ae. sharonensis chromosomes was due to the presence of a translocated segment of a wheat chromosome. — Substitution lines of the Ae. sharonensis chromosome for wheat homoeologous group 4 were produced and the Ae. sharonensis chromosome thereby designated 4 S ^l .     

Molecular cloning and characterization of double-stranded cDNA coding for bovine chymosin

A full-length cDNA copy of the mRNA encoding calf chymosin (also known as rennin), a proteolytic enzyme with commercial importance in the manufacture of cheese, has been cloned in an f1 bacteriophage vector. The nucleotide sequence of the cDNA was determined, and translation of that sequence into amino acids predicts that the zymogen prochymosin is actually synthesized in vivo as preprochymosin with a 16 amino acid signal peptide. In vitro translation of total poly(A)-enriched RNA from the calf fourth stomach (abomasum) and immunoprecipitation with antichymosin antiserum revealed that a form of chymosin (probably preprochymosin judging from the M_r-value) is the major in vitro translation product of RNA from that tissue. Gel-transfer hybridization of restriction endonuclease-cleaved bovine chromosomal DNA with labeled cDNA probes indicated that the two known forms of chymosin, A and B, must be products of two different alleles of a single chymosin gene.     

橡胶延伸因子基因及3'端非编码区的克隆与序列分析

橡胶延伸因子ＲＥＦ（Ｒｕｂｂｅｒ Ｅｌｏｎｇａｔｉｏｎ Ｆａｃｔｏｒ）是橡胶生物合成中最重要的酶之一．作者利用ＲＥＦ基因序列设计并合成引物． 通过提取胶乳总ＲＮＡ 用ＲＴ法合成ｃＤＮＡ 后,通过ＰＣＲ技术扩增并克隆了ＲＥＦ基因和３端非编码区． 序列测定结果表明,ＲＥＦ基因全长４１４ 个碱基,编码１３８ 个氨基酸,３端非编码区长１１２ ｂｐ． 与Ｇｏｙｖａｅｒｔｓ Ｅ 等人发表的序列比较：ＲＥＦ基因同源率为１００％ ,３端非编码区有２ ｂｐ 的差异,同源率为９８％ ． 将所克隆的ＲＥＦ基因及３非编码区进行地高辛标记, 对胶乳和叶片总ＲＮＡ 进行点杂交分析,结果表明,胶乳总ＲＮＡ 呈阳性反应,叶片总ＲＮＡ 则呈阴性反应．     

The motility and dynamic properties of intermediate filaments and their constituent proteins

Intermediate filament (IF) proteins exist in multiple structural forms within cells including mature IF, short filaments or 'squiggles', and non-filamentous precursors called particles. These forms are interconvertible and their relative abundance is IF type, cell type- and cell cycle stage-dependent. These structures are often associated with molecular motors, such as kinesin and dynein, and are therefore capable of translocating through the cytoplasm along microtubules. The assembly of mature IF from their precursor particles is also coupled to translation. These dynamic properties of IF provide mechanisms for regulating their reorganization and assembly in response to the functional requirements of cells. The recent findings that IF and their precursors are frequently associated with signaling molecules have revealed new functions for IF beyond their more traditional roles as mechanical integrators of cells and tissues.     

Vocal divergence is concordant with genomic evidence for strong reproductive isolation in grasshopper mice (Onychomys)

Behavioral barriers to gene flow often evolve faster than intrinsic incompatibilities and can eliminate the opportunity for hybridization between interfertile species. While acoustic signal divergence is a common driver of premating isolation in birds and insects, its contribution to speciation in mammals is less studied. Here we characterize the incidence of, and potential barriers to, hybridization among three closely related species of grasshopper mice (genus Onychomys). All three species use long‐distance acoustic signals to attract and localize mates; Onychomys arenicola and Onychomys torridus are acoustically similar and morphologically cryptic whereas Onychomys leucogaster is larger and acoustically distinct. We used genotyping‐by‐sequencing (GBS) to test for evidence of introgression in 227 mice from allopatric and sympatric localities in the western United States and northern Mexico. We conducted laboratory mating trials for all species pairs to assess reproductive compatibility, and recorded vocalizations from O. arenicola and O. torridus in sympatry and allopatry to test for evidence of acoustic character displacement. Hybridization was rare in nature and, contrary to prior evidence for O. torridus/O. arenicola hybrids, only involved O. leucogaster and O. arenicola. In contrast, laboratory crosses between O. torridus and O. arenicola produced litters whereas O. leucogaster and O. arenicola crosses did not. Call fundamental frequency in O. torridus and O. arenicola was indistinguishable in allopatry but significantly differentiated in sympatry, a pattern consistent with reproductive character displacement. These results suggest that assortative mating based on a long‐distance signal is an important isolating mechanism between O. torridus and O. arenicola and highlight the importance of behavioral barriers in determining the permeability of species boundaries.     

A repressor element in the 5'-untranslated region of human Pax5 exon 1A

Five members of the RecQ helicase family, RECQL, WRN, BLM, RTS and RECQL5, have been found in human and three of them (WRN, BLM and RTS) were disclosed to be the genes responsible for Werner, Bloom and Rothmund–Thomson syndromes, respectively. RECQL5 (RecQ helicase protein-like 5) was isolated as the fifth member of the family in humans through a search of homologous expressed sequence tags. The gene is expressed with at least three alternative splicing products, , β and γ. Here, we isolated mouse RECQL5β and determined the DNA sequence of full-length cDNA as well as the genome organization and chromosome locus. The mouse RECQL5β gene consists of 2949 bp coding 982 amino acid residues. Comparison of amino acid sequence among human (Homo sapiens), mouse (Mus musculus), Drosophila melanogaster and Caenorhabditis elegans RECQL5β homologs revealed three portions of highly conserved regions in addition to the helicase domain. Nineteen exons are dispersed over 40 kbp in the genome and all of the acceptor and donor sites for the splicing of each exon conform to the GT/AG rule. The gene is localized to the mouse chromosome 11E2, which has a syntenic relation to human 17q25.2-q25.3 where human RECQL5β exists. Our genetic characterizations of the mouse RECQL5β gene will contribute to functional studies on the RECQL5β products.     

Phylogenetic and genomic relationships in Setaria italica and its close relatives based on the molecular diversity and chromosomal organization of 5S and 18S-5.8S-25S rDNA genes

We have analyzed the phylogenetic and genomic relationships in the genus Setaria Beauv. including diploid and tetraploid species, by means of the molecular diversity of the 5S rDNA spacer and chromosomal organization of the 5S and 18S-5.8S-25S rDNA genes. PCR amplification of the 5S rDNA sequences gave specific patterns. All the species studied here share a common band of about 340 bp. An additional band of an approximately 300-bp repeat unit was found for Setaria verticillata and the Chinese accessions of Setaria italica and Setaria viridis. An additional band of 450 bp was found in the sole species Setaria faberii. Fluorescent in situ hybridization was used for physical mapping of the 5S and 18S-5.8S-25S rDNA genes and showed that they are localized at two separate loci with no polymorphism of chromosome location among species. Two chromosome pairs carrying the 5S and 18S-5.8S-25S rDNA clusters can now be unambiguously identified using FISH. Phylogenetic trees based on the variation of the amplified 5S rDNA sequences showed a clear separation into four groups. The clustering was dependent on the genomic composition (genome A versus genome B) and confirmed the closest relationship of S. italica and S. viridis accessions from the same geographical region. Our results confirm previous hypotheses on the domestication centers of S. italica. They also show the wide difference between the A and B genomes, and even clarify the taxonomic position of S. verticillata. Received: 28 August 2000 / Accepted: 27 January 2001     

Variation in DNA-ploidy Levels of Reynoutria Taxa in the Czech Republic

The genus Reynoutria is represented by four taxa in the Czech Republic: Reynoutria japonica var. japonica, R. japonica var. compacta, R. sachalinensis and R. xbohemica. By using flow cytometry, cytological variability within the genus is described based on 257 Reynoutria samples. The varieties of R. japonica are cytologically uniform, var. japonica is exclusively octoploid (2n = 8x = 88) and var. compacta occurs only as a tetraploid (2n = 4x = 44), but R. sachalinensis and R. xbohemica exhibit some variation in chromosome numbers. Reynoutria sachalinensis is predominantly tetraploid (2n = 4 x = 44), but also occurs occasionally as hexaploid and octoploid cytotypes. The most common ploidy level in R. xbohemica is hexaploid (2n = 6x = 66), but tetraploid and octoploid clones were also found. The four taxa occurring in the Czech Republic are described briefly and the possible origins of the cytotypes discussed.