传粉和非传粉榕小蜂线粒体基因组进化差异

[目的]目前关于榕小蜂类群的线粒体基因组报道很少,本研究旨在探讨传粉和非传粉榕小蜂两个群体的线粒体基因组的进化差异.[方法]以15种榕小蜂的线粒体基因组(其中11种的线粒体基因组为新测定)数据为基础,采用比较线粒体基因组学方法,分析榕小蜂的线粒体基因组序列和进化特征.[结果]本研究新测定的11个榕小蜂物种的近全长线粒体...     

Mapping of insertion element IS30 in the Escherichia coli K12 chromosome

Summary We identified seven phage clones containing the insertion element IS30 in a phage library mini-set, which includes 476 clones carrying chromosomal segments that cover almost the entire chromosome ofEscherichia coli K12 W3110 (Kohara et al. 1987). We could assign locations and orientations to four copies of IS30 (namedis30A tois30D) on the W3110 chromosome by restriction analysis of phage DNAs containing them. These IS30s were present at the same locations in chromosomes of both W3110 and anotherE. coli K12 strain JE5519, and thus are assumed to be present in otherE. coli K12 derivatives, including early isolates. Among the IS30 copies found, one (is30B) contained a large deletion and possessed only a 181 by stretch of the right terminal region of IS30.EMBL Accession Number: The EMBL accession number of the sequence reported in this paper is X17345     

Unusual Activation of Cation Disordering by Li/Fe Rearrangement in Triplite LiFeSO4F

It is reported that cation disordering in triplite LiFeSO₄F can be activated by Li/Fe rearrangement that results from irreversible and nondestructive structural changes during the 1st charge/discharge cycle, especially during the charge. This rearrangement decreases the number of edge‐shared FeO₄F₂ connection environments, compared to the pristine material. With this activation, triplite LiFeSO₄F exhibits several unexpected electrochemical features in subsequent cycles; a decrease in open‐circuit voltage indicating the change in thermodynamic property, negligible volumetric change, enhanced Li diffusion, and facile phase transformation pathway. As a consequence, the cation‐disordered triplite LiFeSO₄F achieves superior rate capability up to ≈66 mA h g^?1 at 40 C rate (1.5 min discharge) and has excellent capacity retention for 500 cycles at 5 C charge/5 C discharge rate and for 1200 cycles at 2 C charge/2 C discharge rate. Therefore, triplite LiFeSO₄F can be one of the most promising electrode materials for Li ion batteries.     

Improving Nelumbo nucifera genome assemblies using high‐resolution genetic maps and BioNano genome mapping reveals ancient chromosome rearrangements

Genetic and physical maps are powerful tools to anchor fragmented draft genome assemblies generated from next‐generation sequencing. Currently, two draft assemblies of Nelumbo nucifera, the genomes of ‘China Antique’ and ‘Chinese Tai‐zi’, have been released. However, there is presently no information on how the sequences are assembled into chromosomes in N. nucifera. The lack of physical maps and inadequate resolution of available genetic maps hindered the assembly of N. nucifera chromosomes. Here, a linkage map of N. nucifera containing 2371 bin markers [217 577 single nucleotide polymorphisms (SNPs)] was constructed using restriction‐site associated DNA sequencing data of 181 F₂ individuals and validated by adding 197 simple sequence repeat (SSR) markers. Additionally, a BioNano optical map covering 86.20% of the ‘Chinese Tai‐zi’ genome was constructed. The draft assembly of ‘Chinese Tai‐zi’ was improved based on the BioNano optical map, showing an increase of the scaffold N50 from 0.989 to 1.48 Mb. Using a combination of multiple maps, 97.9% of the scaffolds in the ‘Chinese Tai‐zi’ draft assembly and 97.6% of the scaffolds in the ‘China Antique’ draft assembly were anchored into pseudo‐chromosomes, and the centromere regions along the pseudo‐chromosomes were identified. An evolutionary scenario was proposed to reach the modern N. nucifera karyotype from the seven ancestral eudicot chromosomes. The present study provides the highest‐resolution linkage map, the optical map and chromosome level genome assemblies for N. nucifera, which are valuable for the breeding and cultivation of N. nucifera and future studies of comparative and evolutionary genomics in angiosperms.     

Further investigation of the light chain shifting phenomenon: Light chain replacement through secondary rearrangement induced by lectin stimulation in the hybridoma cell line HB4C5

We found that when the hybridoma cell line HB4C5 was stimulated with wheat germ agglutinin (WGA), loss of production of the original λ light chain occurred, followed by production of new light chain, which mirrored the reaction when stimulated with concanavalin A (ConA). We previously reported that the RAG genes are expressed not only in HB4C5 and its ConA-treated variant subclones, but also in the in the parental Namalwa cells, which are known to be in the plasma state. However, the new λ light chains were expressed only in the HB4C5 cells and not in the parental Namalwa cells. Here we found that the RAG genes are expressed in HB4C5 cells after continuous stimulation with WGA. To further investigate the mechanism of this loss of original λ light chain production by stimulation with lectins in HB4C5 cells, which leads to a sIg-negative subpopulation, we analyzed the differences between HB4C5 and Namalwa cells. In this present study, we found that a 70 kDa phosphorylated protein in HB4C5 cells became undetectable after stimulation with lectins (WGA and ConA), and was not detected in Namalwa cells before or after lectin stimulation. It has been believed that the RAG genes and loss of original λ light chain production are required to induce expression of a new λ light chain in the HB4C5 cells. We suggested that the phosphorylated 70 kDa protein in HB4C5 cells play important roles in regulating the production of new λ light chains which is induced by lectins. This revised version was published online in June 2006 with corrections to the Cover Date.     

A genetic and molecular analysis of P-induced mutations at the glucose-6-phosphate dehydrogenase locus in Drosophila melanogaster

Summary We examined P factor induced mutations of the Zw gene of Drosophila melanogaster in order to learn more about the site specificity of such mutations. Approximately 70000 chromosomes were screened using a powerful positive selection scheme. As only two mutants were discovered, Zw is a cold spot for transposable element insertion. One mutation involved a complex P element associated chromosomal rearrangement which was used to define the orientation of the gene with respect to the centromere of the X chromosome. The second mutation was either a simple, non-dysgenically induced point mutation or a very unstable insertion.     

Conversion of squalene-2(3)epoxide by enzymes of Alnus glutinosa

The incubation of [1-¹⁴C]-squalene-2(3)epoxide ([1-¹⁴C]-SO) with a cell-free extract of Alnus glutinosa gave only cycloartenol in 1% yield.