An atypical epigenetic mechanism affects uniparental expression of Pol IV-dependent siRNAs

Background

Small RNAs generated by RNA polymerase IV (Pol IV) are the most abundant class of small RNAs in flowering plants. In Arabidopsis thaliana Pol IV-dependent short interfering (p4-si)RNAs are imprinted and accumulate specifically from maternal chromosomes in the developing seeds. Imprinted expression of protein-coding genes is controlled by differential DNA or histone methylation placed in gametes. To identify epigenetic factors required for maternal-specific expression of p4-siRNAs we analyzed the effect of a series of candidate mutations, including those required for genomic imprinting of protein-coding genes, on uniparental expression of a representative p4-siRNA locus.

Results

Paternal alleles of imprinted genes are marked by DNA or histone methylation placed by DNA METHYLTRANSFERASE 1 or the Polycomb Repressive Complex 2. Here we demonstrate that repression of paternal p4-siRNA expression at locus 08002 is not controlled by either of these mechanisms. Similarly, loss of several chromatin modification enzymes, including a histone acetyltransferase, a histone methyltransferase, and two nucleosome remodeling proteins, does not affect maternal expression of locus 08002. Maternal alleles of imprinted genes are hypomethylated by DEMETER DNA glycosylase, yet expression of p4-siRNAs occurs irrespective of demethylation by DEMETER or related glycosylases.

Conclusions

Differential DNA methylation and other chromatin modifications associated with epigenetic silencing are not required for maternal-specific expression of p4-siRNAs at locus 08002. These data indicate that there is an as yet unknown epigenetic mechanism causing maternal-specific p4-siRNA expression that is distinct from the well-characterized mechanisms associated with DNA methylation or the Polycomb Repressive Complex 2.     

Some observations on the morphological evidence for mechanism of the bile secretion

The morphological evidence of the intracellular route of bile secretion was investigated in the liver of goldfish (Carassius auratus) as revealed by electron microscopy. Smooth surfaced tubules or cisterns within or adjacent to the Golgi apparatus showed linear saccular forms and contained sparse particulate or cloudy materials of low electron density. The isolated vacuoles were restrictedly found between the Golgi apparatus and the intracellular bile canaliculus or hepatocytic side at the zone of transition. These vacuoles showed no reaction for acid phosphatase activity, and contained only a few cloudy materials similar to those found in the saccular tubules and within the bile canaliculus. Some of these vacuoles fused with the luminal cytolemmas of the bile canaliculus. Bases on these findings, it was assumed that these vacuoles are structures participating in transport and secretion of bile constituents and derive from the linearly sacculated tubules or cisterns in the Golgi zone. Duct cells showed no morphological evidence to suggest bile secretion.     

Lafutidine versus Lansoprazole in Combination with Clarithromycin and Amoxicillin for One versus Two Weeks for Helicobacter pylori Eradication in Korea

Background and Aims: Lafutidine is a novel H₂‐receptor antagonist with gastroprotective activity that includes enhancement of gastric mucosal blood flow. The aim of the present study was to test the efficacy of 7‐ or 14‐day lafutidine–clarithromycin–amoxicillin therapy versus a lansoprazole‐based regimen for Helicobacter pylori eradication. Methods: Four hundred and sixty‐three patients with H. pylori‐infected peptic ulcer disease were randomized to one of four regimens: (1) lafutidine (20 mg b.i.d.), clarithromycin (500 mg b.i.d.) and amoxicillin (1000 mg b.i.d.) for 7 days (the 7LFT group) or (2) for 14 days (the 14LFT group); (3) lansoprazole (30 mg b.i.d.), clarithromycin (500 mg b.i.d.), and amoxicillin (1000 mg b.i.d.) for 7 days (the 7LPZ group); or (4) for 14 days (the 14LPZ group). The eradication rates, drug compliance, and adverse effects among the four regimens were compared. Results: The eradication rates by the intention‐to‐treat and per‐protocol analyses in the 7LFT and 7LPZ groups were 76.5% and 81.6%, and 76.9% and 82.0% (p = .94 and .95), respectively. The eradication rates by intention‐to‐treat and per‐protocol analyses in the 14LFT and 14LPZ groups were 78.2% and 82.2%, and 80.4% and 85.9% (p = .70 and .49), respectively. The treatment duration for 7 days or 14 days did not affect the eradication rates. In addition, the adverse effect rates and discontinuation rates were similar among the four groups. Furthermore, the ulcer cure rate and symptom response rate were similar in the lafutidine and lansoprazole groups. Conclusion: The results of this study showed that lafutidine–clarithromycin–amoxicillin therapy was a safe and effective as lansoprazole‐based triple therapy for the eradication rate of H. pylori, and could be considered as an additional treatment option.     

Functional nucleotides of U5 LTR determining substrate specificity of prototype foamy virus integrase

In order to study functional nucleotides in prototype foamy virus (PFV) DNA on specific recognition by PFV integrase (IN), we designed chimeric U5 long terminal repeat (LTR) DNA substrates by exchanging comparative sequences between human immunodeficiency virus type-1 (HIV-1) and PFV U5 LTRs, and investigated the 3'-end processing reactivity using HIV-1 and PFV INs, respectively. HIV-1 IN recognized the nucleotides present in the fifth and sixth positions at the 3'-end of the substrates more specifically than any other nucleotides in the viral DNA. However, PFV IN recognized the eighth and ninth nucleotides as distinctively as the fifth and sixth nucleotides in the reactions. In addition, none of the nucleotides present in the twelfth, sixteenth, seventeenth, eighteenth, nineteenth, and twentieth positions were not differentially recognized by HIV-1 and PFV INs, respectively. Therefore, our results suggest that the functional nucleotides that are specifically recognized by its own IN in the PFV U5 LTR are different from those in the HIV-1 U5 LTR in aspects of the positions and nucleotide sequences. Furthermore, it is proposed that the functional nucleotides related to the specific recognition by retroviral INs are present inside ten nucleotides from the 3'-end of the U5 LTR.     

Insecticide susceptibility of Ephemera orientalis (Ephemeroptera: Ephemeridae) and two mosquito species,Anopheles sinensis and Culex pipiens in the Republic of Korea

Field-collected populations of mayflies, Ephemera orientalis were tested for susceptibility to 10 different insecticides using a direct-contact mortality bioassay. Ephemera orientalis subimagoes were susceptible to the insecticides chlorpyrifos, fenitrothion and chlorfenapyr with LD₅₀ values of 69.7, 78.8 and 81.9 μg/♀, and adults had LD₅₀ values of 71.9, 78.8 and 85.4 μg/♀, respectively. Susceptibility ratios (SRs) of subimagoes and adults of E. orientalis to the 10 insecticides were 1.0 to1.2 folds. The mayflies showed higher susceptibility to organophosphates than to pyrethroids. The SRs of Anopheles sinensis to E. orientalis were 514 to 1438 folds higher for organophosphates (LD₅₀ values of 0.05 to 0.23 μg/♀) and 62 to 1155 folds higher for pyrethroids (LD₅₀ values of 0.13 to 2.41 μg/♀). The SRs of Culex pipiens to E. orientalis were 606 to 3595 folds higher for organophosphates with LD₅₀ values of 0.02–0.17 μg/♀ and 81 to 1365 folds higher for pyrethroids with LD₅₀ values of 0.11–1.83 μg/♀. These results indicate that the use of ineffective insecticides will result in unsatisfactory control against field populations of the subimagoes and adults of E. orientalis.     

A highly efficient method for porcine cloning by nuclear transfer using in vitro-matured oocytes

To date, the efficiency of pig cloning by nuclear transfer of somatic cell nuclei has been extremely low, with less than 1% of transferred embryos surviving to term. Even the utilization of complex procedures such as two rounds of nuclear transfer has not resulted in greater overall efficiencies. As a result, the applicability of the technology for the generation of transgenic and cloned animals has not moved forward rapidly. We report here a simple nuclear transfer protocol, utilizing commercially available in vitro-matured oocytes, that results in greater than 5% overall cloning efficiency. Of five recipients receiving nuclear transfer embryos produced with a fetal fibroblast cell line as nuclear donor, all five established pregnancies by day 28 (100%), and 4/5 (80%) went to term. Efficiencies for each transfer were 7% (9 piglets/128 doublets transferred), 5% (5/100), 12% (7/59), and 6.6% (7/106). The overall efficiency in all recipients was 5.5% and in pregnant recipients 7.7%, with a total of 28 cloned piglets produced. With the average fusion rate being 58%, the percentage of fused doublets producing a live piglet approached 12%. The method described here can be undertaken by a single micromanipulator at a reasonable cost, and should facilitate the broad utilization of porcine cloning technology in transgenic and nontransgenic applications.     

Fluid shear regulates the kinetics and receptor specificity of Staphylococcus aureus binding to activated platelets

The interaction between surface components on the invading pathogen and host cells such as platelets plays a key role in the regulation of endovascular infections. However, the mechanisms mediating Staphylococcus aureus binding to platelets under shear remain largely unknown. This study was designed to investigate the kinetics and molecular requirements of platelet-S. aureus interactions in bulk suspensions subjected to a uniform shear field. Hydrodynamic shear-induced collisions augment platelet-S. aureus binding, which is further potentiated by platelet activation with stromal derived factor-1beta. Peak adhesion efficiency occurs at low shear (100 s(-1)) and decreases with increasing shear. The molecular interaction of platelet alpha(IIb)beta(3) with bacterial clumping factor A through fibrinogen bridging is necessary for stable bacterial binding to activated platelets under shear. Although this pathway is sufficient at low shear (相似文献   

A new factor in the Aedes aegypti immune response: CLSP2 modulates melanization

Microbial infections in the mosquito Aedes aegypti activate the newly identified CLSP1 and CLSP2 genes, which encode modular proteins composed of elastase-like serine protease and C-type lectin domains. These genes are predominantly regulated by the immune deficiency pathway, but also by the Toll pathway. Silencing of CLSP2, but not CLSP1, results in the activation of prophenoloxidase (PPO), the terminal enzyme in the melanization cascade, suggesting that CLSP2 is a negative modulator of this reaction. Haemolymph PPO activation is normally inhibited in the presence of Plasmodium parasites, but in CLSP2-depleted mosquitoes, the Plasmodium-induced block of melanization is reverted, and these mosquitoes are refractory to the parasite. Thus, CLSP2 is a new component of the mosquito immune response.     

Genome sequence of strain TW25, a novel member of the genus Ornithinibacillus in the family Bacillaceae

Ornithinibacillus sp. strain TW25, belonging to the family Bacillaceae, was isolated from a dead ark clam during a mass mortality event. Here, the draft genome sequence of strain TW25 (3,843,870 bp, with a G+C content of 36.7%) is reported. This is the first Ornithinibacillus genome to be sequenced.