Comparative RFLP mapping of meadow and tall fescue

 Molecular markers based on restriction fragment length polymorphism (RFLP) were used to construct a genetic linkage map in diploid meadow fescue, Festuca pratensis Huds. (2n=2x=14, genomic designation PP), and to compare its genomic relationship with a related species, hexaploid tall fescue (Festuca arundinacea Schreb.; 2n=6x=42, PPG₁G₁G₂G₂). Using a collection of 66 tall-fescue (heterologous) markers, an RFLP linkage map was constructed in F. pratensis. This map, which has a total length of 280.1 cM, includes seven linkage groups. A comparison of 33 markers that were mapped in both F. pratensis and F. arundinacea detected highly conserved linkage groups between these two species. Our data are consistent with the proposal that one of the genomes of F. arundinacea was derived from F. pratensis. However, since significant changes in marker sequences, map distances, and homoeologous linkage groups were also detected between the two species, it appears that the P genome diverged substantially during evolution from the diploid to the hexaploid Festuca. Received: 23 May 1997 / Accepted: 15 January 1998     

野生稻基因组随机扩增多态性DNA(RAPD)分析

用18个随机引物对2份栽培稻、12份包含有六个基因组型的野生稻DNA进行了扩增,共获得147个多态性DNA片断,把这些多态性DNA片断作为遗传位点用UPGMA法计算出各材料间的遗传相似性系数,并作了聚类分析．主要结果如下：1普通野生稻同栽培稻的亲缘关系很近,其中江永普通野生稻更接近于粳稻．2．CCDD组的Oryzalatifolia和EE组的O．australiensis遗传多态性相似。3．B、C、D、E组的遗传多态性相似,组成一个复合体,此复合体与A组的遗传多态性也相似,而F组则相距较远．4．O．mcyeriana和Rhynchofyzasabulata尚未确定组型,RAPD测定结果表明,前者与其它组型的种亲缘关系较远,后者则与AC复合体的种较近．     

Histones and nucleosomes in Archaea and Eukarya: a comparative analysis

Archaeal histones from mesophilic, thermophilic, and hyperthermophilic members of the Euryarchaeota have primary sequences, the histone fold, tertiary structures, and dimer formation in common with the eukaryal nucleosome core histones H2A, H2B, H3, and H4. Archaeal histones form nucleoprotein complexes in vitro and in vivo, designated archaeal nucleosomes, that contain histone tetramers and protect approximately 60 base pairs of DNA from nuclease digestion. Based on the sequence and structural homologies and experimental data reviewed here, archaeal nucleosomes appear similar, and may be homologous in evolutionary terms and function, to the structure at the center of the eukaryal nucleosome formed by the histone (H3+H4)₂ tetramer. Received: January 22, 1998 / Accepted: February 16, 1998     

Analysis of the genome of the gram-negative moderate halophiles Halomonas and Chromohalobacter by using pulsed-field gel electrophoresis

The genomes of 11 moderately halophilic bacteria belonging to the genera Halomonas and Chromohalobacter have been analyzed by restriction endonuclease digestion and pulsed-field gel electrophoresis (PFGE). By using the infrequently cutting restriction endonucleases SpeI and SwaI, highly characteristic fingerprintings were obtained for each of the isolates studied. On the basis of the lengths of the SpeI and SwaI fragments, separated by PFGE, the genome size of the 11 strains studied was estimated. The genome size for 8 Halomonas strains ranged from 1450 to 2830 kb, whereas for the 3 Chromohalobacter strains studied it ranged from 1770 to 2295 kb. Finally, we show that macrorestriction fingerprints could be a useful tool to elucidate the taxonomic position of bacteria belonging to the Halomonas–Deleya complex. Received: October 13, 1997 / Accepted: May 12, 1998     

Estimation of genome sizes of hyperthermophiles

Genomes of various hyperthermophilic and extremely thermophilic prokaryotes were analyzed with respect to size, physical organization, and 16S rDNA copy number. Our results show that all the genomes are circular, and they are in the size range of 1.6–1.8 Mb for Pyrodictium abyssi, Methanococcus igneus, Pyrobaculum aerophilum, Archaeoglobus fulgidus, Archaeoglobus lithotrophicus, and Archaeoglobus profundus (the two bacteria Fervidobacterium islandicum and Thermosipho africanus possess genomes of 1.5-Mb size). A systematic study of all validly described species of the order Sulfolobales revealed the existence of two classes of genome size for these archaea, correlating with phylogenetic analyses. The Metallosphaera–Acidianus group, plus Sulfolobus metallicus, have genomes of ca. 1.9 Mb; the other members of the order Sulfolobales group possess genomes >2.7 Mb. The special case of Stygiolobus azoricus is discussed. Received: August 10, 1997 / Accepted: January 1, 1998