Variation in the Frequency and Extent of Hybridization between Leucosceptrum japonicum and L. stellipilum (Lamiaceae) in the Central Japanese Mainland

Variations in the frequency and extent of hybridization among mixed populations located in the same contact zone provide natural laboratories for the study of extrinsic reproductive isolation maintaining species integrity. In this study, we examined the pattern of hybridization between L. japonicum and L. stellipilum among mixed populations in different localities of a contact zone. The genetic structures from three sympatric populations and six mixed populations in the hybrid zone, and five reference populations far from the contact zone, were characterized using 10 neutral nuclear microsatellite markers. Evidence from genetic distance-based clustering analysis, the frequency distribution of admixture proportion values, and the hybrid category assignment approaches indicated that the frequency and extent of hybridization varied considerably among populations in the contact zone between L. japonicum and L. stellipilum. One likely explanation is that variation in exogenous (ecological) selection among populations might contribute to differences in frequency and extent of hybridization. The present study will facilitate future research exploring the evolution of reproductive isolation between L. japonicum and L. stellipilum.     

S-adenosylmethionine stimulates fatty acid metabolism-linked gene expression in porcine muscle satellite cells

Evidence indicates that both S-adenosylmethionine (SAMe) metabolism and intramuscular fat are associated with insulin resistance and type II diabetes. However, it is still unknown whether SAMe have effects on intramuscular adipogenesis. The present study investigated the roles of SAMe in the adipogenic differentiation of porcine muscle satellite cells. Cells isolated from neonatal pig muscle were treated with different concentrations of SAMe (0, 0.5 and 1.0 mM) for 24 h, induced for a 9-day adipogenic differentiation and were finally stained by oil red O staining. The adipocyte determination and differentiation factor-1 (ADD1) and peroxisome proliferator-activated receptor gamma (PPARγ) mRNA and protein were stimulated by SAMe treatment in a dose-dependent manner. Lipoprotein lipase (LPL) mRNA and protein were enhanced in 1.0 mM treatment group, compared with the control. No significant difference was observed in the intracellular lipid content among treatments. These results provide evidence that SAMe may be associated with intramuscular adipogenesis and indicate a novel action of SAMe in fat metabolism.     

Overexpression of malate dehydrogenase in transgenic tobacco leaves: enhanced malate synthesis and augmented Al-resistance

Numerous studies with transgenic plants have demonstrated that overexpression of enzymes related to organic acid metabolism under the control of CaMV 35S promoter increased organic acid exudation and Al-resistance. The synthesis of organic acids requires a large carbon skeleton supply from leaf photosynthesis. Thus, we produced transgenic tobacco overexpressing cytosolic malate dehydrogenase (MDH) cDNA from Arabidopsis thaliana (amdh) and the MDH gene from Escherichia coli (emdh), respectively, under the control of a leaf-specific light-inducible promoter (Rubisco small subunit promoter, PrbcS) in the present study. Our data indicated that an increase (120–130%) in MDH-specific activity in leaves led to an increase in malate content in the transgenic tobacco leaves and roots as well as a significant increase in root malate exudation compared with the WT plants under the acidic (pH 4.5) conditions irrespective of 300 μM Al³⁺ stress absence or presence. After being exposed to 25 μM Al³⁺ in a hydroponic solution, the transgenic plants exhibited stronger Al-tolerance than WT plants and the degree of A1 tolerance in the transgenic plants corresponded with the amount of malate secretion. When grown in an Al-stress perlite medium, the transgenic tobacco lines showed better growth than the WT plants. The results suggested that overexpression of MDH driven by the PrbcS promoter in transgenic plant leaves enhanced malate synthesis and improved Al-resistance.     

Characterization of the interactions of a bifunctional inhibitor with alpha-thrombin by molecular modelling and peptide synthesis.

A potent thrombin inhibitor, [D-Phe45, Arg47] hirudin 45-65, that contains an active site-directed sequence D-Phe-Pro-Arg-Pro, an exosite specific fragment hirudin 55-65 (H55-65) and a linker portion hirudin 49-54, was designed based on the hirudin sequence [DiMaio et al. (1990) J. Biol. Chem., 265, 21698-21798]. A three-dimensional model of the complex between the B-chain of human thrombin and the inhibitor [D-Phe45, Arg47] hirudin 45-65 was constructed using molecular modelling starting from the X-ray C alpha coordinates of the thrombin-hirudin complex and the NMR-derived structure of the thrombin-bound hirudin 55-65. The contribution of the H49-54 fragment to the thrombin-inhibitor interaction was deduced by examining a series of analogs containing single glycine substitution and analogs with reduced number of residues within the linker. The results were consistent with the molecular modelling observations i.e. the H49-54 fragment serves the role of a spacer in the binding interaction and could be replaced by four glycine residues. The studies on the interaction of the exosite-directed portion of the inhibitor with thrombin using a series of synthetic H55-65 analogs demonstrated that residues AspH55 to ProH60 play a major role in binding to human thrombin where the side chains of PheH56, IleH59 and GluH57 showed critical contributions. Molecular modelling suggested that these side chains may contribute to inter- and intramolecular hydrophobic and electrostatic interactions, respectively.     

Identification of Key Factors Involved in the Biosorption of Patulin by Inactivated Lactic Acid Bacteria (LAB) Cells

The purpose of this study was to identify the key factors involved in patulin adsorption by heat-inactivated lactic acid bacteria (LAB) cells. For preventing bacterial contamination, a sterilization process was involved in the adsorption process. The effects of various physical, chemical, and enzymatic pre-treatments, simultaneous treatments, and post-treatments on the patulin adsorption performances of six LAB strains were evaluated. The pre-treated cells were characterized by scanning electron microscopy (SEM). Results showed that the removal of patulin by viable cells was mainly based on adsorption or degradation, depending on the specific strain. The adsorption abilities were widely increased by NaOH and esterification pre-treatments, and reduced by trypsin, lipase, iodate, and periodate pre-treatments. Additionally, the adsorption abilities were almost maintained at pH 2.2–4.0, and enhanced significantly at pH 4.0–6.0. The effects of sodium and magnesium ions on the adsorption abilities at pH 4 were slight and strain-specific. A lower proportion of patulin was released from the strain with higher adsorption ability. Analyses revealed that the physical structure of peptidoglycan was not a principal factor. Vicinal OH and carboxyl groups were not involved in patulin adsorption, while alkaline amino acids, thiol and ester compounds were important for patulin adsorption. Additionally, besides hydrophobic interaction, electrostatic interaction also participated in patulin adsorption, which was enhanced with the increase in pH (4.0–6.0).     

元谋干热河谷植被的类型研究 Ⅱ.群丛以下单位

本文用法瑞植物社会学学派的方法,并经主分量分析验证,对元谋干热河谷的植被进行了重点在群丛及其以下单位的系统分类研究。结果得到9个群丛以及各群丛之下的6个亚群丛、3个群丛变型和两个群丛相的一套系统单位。