The conjugative plasmid SLP2 of Streptomyces lividans is a 50 kb linear molecule

The SLP2 plasmid had previously been demonstrated genetically to exist In Streptomyces lividans by its ability to promote conjugation and to elicit‘pocks’on recipient (SLP2^?) cultures, but it had not been physically detected. Using pulsed-field gel electrophoresis, a 50kb linear DNA was isolated from SLP2⁺ but not SLP2^? strains of S. lividans, and from Streptomyces coelicolor and Streptomyces parvulus strains to which SLP2 had been transferred by conjugation or transformation. We conclude that this linear DNA is SLP2. The terminal fragments of SLP2 were cloned. The determined sequences revealed a 44 bp imperfect terminal inverted repeat. The terminal 12 bp sequence of SLP2 was identical to those of two other Streptomyces linear plasmids, pSLA2 and pSCL, and similar to the terminal sequences of another Streptomyces linear plasmid, SCP1. The termini of SLP2 DNA were resistant to digestion by λ exonuclease and ExoIII. A truncated (probably crippled) copy of Tn4811 is present on the plasmid. While the SLP2 plasmid exists as a tree form in the host, a 15.7 kb sequence corresponding to the segment of SLP2 from Tn4811 to the right terminus is also present (at a copy number similar to the free form) elsewhere in the genome of S. lividans. Furthermore, SLP2 is partially homologous to a newly discovered 650 kb linear plasmid in S. parvulus.     

ATP稳定肌浆网膜蛋白色氨酸相关构象的机理的探讨

在无ＡＴＰ存在时,带相同正电荷、但饱和不同的两种胺类两亲物,即Ｃ１８饱和的硬脂胺与单不饱和的油胺引起肌浆网蛋白内源荧光强度降低,当ＡＴＰ或一些阴离子化合物先与肌浆网作用,再加入硬脂胺或油胺,则肌浆网蛋白内源荧光下降幅度明显减小,即存在拮抗作用。腺苷对硬脂胺或油胺均无此拮抗作用。肌浆网与油胺先保温,再加入ＡＴＰ或阴离子化合物,ＡＴＰ仍有拮抗,阴离子化合物对油胺则无拮抗作用。然而在肌浆网钙泵蛋白上存在     

外显子与内含子序列分维的双碱基研究

引入碱基间的关联,研究了外显子和内含子序列以双碱基为单位的分维,我们发现在这种情况下,外显子和内显子序列在短程和中程存在自相似性并分别定义了这两个区域的分维。结果表明,短程的分维值Ｄｇ一般比中程的Ｄｍ大,外显子的两个分维值比内含子大。我们改变双联体的位相而分维却不变,这反映出在双联体基础上,外显子的不规则性大于内含子,短程的不规则性大于中程,外显子和内含子序列对以２为周期的结构没有位相的特异性。     

LEP and LEPR are possibly a double-edged sword for wound healing

Wound healing is a complex and error-prone process. Wound healing in adults often leads to the formation of scars, a type of fibrotic tissue that lacks skin appendages. Hypertrophic scars and keloids can also form when the wound-healing process goes wrong. Leptin (Lep) and leptin receptors (LepRs) have recently been shown to affect multiple stages of wound healing. This effect, however, is paradoxical for scarless wound healing. On the one hand, Lep exerts pro-inflammatory and profibrotic effects; on the other hand, Lep can regulate hair follicle growth. This paper summarises the role of Lep and LepRs on cells in different stages of wound healing, briefly introduces the process of wound healing and Lep and LepRs, and examines the possibility of promoting scarless wound healing through spatiotemporal, systemic, and local regulation of Lep levels and the binding of Lep and LepRs.     

Evaluation of housekeeping genes as references for quantitative real-time PCR analysis of European eel,Anguilla anguilla

Eels are important aquaculture species for which an increasing number of reference genes are being identified and applied. In this study, five housekeeping genes [RPL7 (ribosomal protein L7), 18 S (18 S ribosomal RNA), EF1A (elongation factor 1α), ACTB (β-actin) and GAPDH (glyceraldehyde-3-phosphate dehydrogenase)] were chosen to evaluate their reliability as reference genes for quantitative real-time PCR (qPCR) for the study of Anguilla anguilla. The expression of the selected genes in different eel tissues was determined using qPCR at different growth stages or upon challenge by Anguillid herpesvirus (AngHV), and the expression levels of these genes were then compared and evaluated using the geNorm and NormFinder algorithms. Then, RefFinder was used to comprehensively rank the examined housekeeping genes. Interestingly, the expression of the evaluated housekeeping genes exhibited tissue-dependent and treatment-dependent variations. In different growth periods A. anguilla tissues, the most stable genes were the following: ACTB in mucus; 18 S in skin and kidney; RPL7 in muscle, gill, intestine and brain; EF1A in heart and liver; and GAPDH in spleen. In contrast, in AngHV-challenged A. anguilla tissues, the most stable genes were the following: 18 S in mucus; RPL7 in skin, gill, heart, spleen, kidney and intestine; EF1A in muscle and liver; and ACTB in brain. Further comparison analysis indicated that the expression of RPL7 and EF1A was stable in multiple A. anguilla tissues in different growth periods and in eels challenged by AngHV. Nonetheless, the expression level of GAPDH in eel tissues was lower, and it was unstable in several tissues. These results indicated that the selection of reference genes for qPCR analysis in A. anguilla should be made in accordance with experimental parameters, and both RPL7 and EF1A could be used as reference genes for qPCR study of A. anguilla at different growth stages or upon challenge by AngHV. The reference genes identified in this study could improve the accuracy of qPCR data and facilitate further studies aimed at understanding the biology of eels.     

Three-dimensional structures of the central regulatory proteins of the bacterial phosphotransferase system,HPr and enzyme IIAglc

Enzyme IIA and HPr are central regulatory proteins of the bacterial phosphoenolpyruvate:sugar phosphotransferase (PTS) system. Three-dimensional structures of the glucose enzyme IIA domain (IIA^glc) and HPr of Bacillus subtilis and Escherichia coli have been studied by both X-ray crystallography and Nuclear Magnetic Resonance (NMR) Spectroscopy. Phosphorylation of HPr of B. subtilis and IIA^glc of E. coli have also been characterized by NMR spectroscopy. In addition, the binding interfaces of B. subtilis HPr and IIA^glc have been identified from backbone chemical shift changes. This paper reviews these recent advances in the understanding of the three-dimensional structures of HPr and IIA^glc and their interaction with each other. © 1993 Wiley-Liss, Inc.     

Effects of ROS and caspase-3-like protein on the growth and aerenchyma formation of Potamogeton perfoliatus stem

Protoplasma - Aerenchyma formation plays an important role in the survival of Potamogeton perfoliatus in submerged environment. To understand the regulatory role of reactive oxygen species (ROS)...     

Comment on “Is Yuan in China’s Three Gorges a Gibbon or a Langur?”

International Journal of Primatology -     

β-Cyclodextrin-Based Nitrosoglutathione Improves the Storage Quality of Peach by Regulating the Metabolism of Endogenous Nitric Oxide,Hydrogen Sulfide,and Phenylpropane

Nitrosoglutathione (GSNO) and β-cyclodextrin (β-CD) exhibit positive roles in regulating fruit quality. However, there are few reports about the effects of GSNO and β-CD on enhancing storability and boosting nitric oxide (NO), hydrogen sulfide (H₂S), and phenylpropane metabolism in fruits during storage. “Xintaihong” peach were treated with 0.5, 1.0, 1.5 mmol L⁻¹ GSNO in 0.5% (w/v) β-CD solution (GSNO/β-CD). The effects of GSNO/β-CD on endogenous NO, H₂S, and phenylpropane metabolism were investigated. Treatment with GSNO/β-CD increased the color difference of peach and inhibited the increase of respiratory intensity, weight loss, and relative conductivity. Treatment with 1.0 mmol L⁻¹ GSNO/β-CD increased the nitric oxide synthase (NOS-like) activity and L-arginine content, thereby promoting the accumulation of endogenous NO. By improving the activities of L-cysteine desulfhydrylase (L-CD), O-acetylserine sulfur lyase (OAS-TL), serine acetyltransferase (SAT), GSNO/β-CD increased the content of endogenous H₂S in peach. Treatment with GSNO/β-CD increased the activities of phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL), and cinnamic acid-4-hydroxylase (C4H), promoted the increase of total phenols, flavonoids, and lignin in peach. These results indicated that GSNO/β-CD treatment better maintained the quality of peach by improving the metabolism of endogenous NO, H₂S, and phenylpropane during storage.