基于RAD高通量测序的蓝花楹群体遗传分析

为了解蓝花楹(Jacaranda mimosifolia)种质资源的遗传多样性和群体遗传结构,对168份种质材料进行RAD-seq测序,构建了系统进化树并进行主成分、群体结构和遗传多样性分析。结果表明,比对参考基因组平均比对率为81.02%,平均测序深度23.18×,最终获得45 552个高质量的SNPs。群体遗传结构分析表明,供试蓝花楹可划分为2个大的类群,来自川、渝地区的种质材料基本归为一类;其余地区归为另一类。19个地区的蓝花楹在SNP水平上的遗传多样性较高,云南昆明(YNKM)居群的核苷酸多样性(π)期望杂合度(He)最大,表现出最高的遗传多样性。因此,来自川、渝地区的蓝花楹具有相对较近的亲缘关系,推断来自同一祖先,而其余地区的种质可能是随机引种栽培。     

Molecular Control of TiO(2)-NPs Toxicity Formation at Predicted Environmental Relevant Concentrations by Mn-SODs Proteins

With growing concerns of the safety of nanotechnology, the in vivo toxicity of nanoparticles (NPs) at environmental relevant concentrations has drawn increasing attentions. We investigated the possible molecular mechanisms of titanium nanoparticles (Ti-NPs) in the induction of toxicity at predicted environmental relevant concentrations. In nematodes, small sizes (4 nm and 10 nm) of TiO(2)-NPs induced more severe toxicities than large sizes (60 nm and 90 nm) of TiO(2)-NPs on animals using lethality, growth, reproduction, locomotion behavior, intestinal autofluorescence, and reactive oxygen species (ROS) production as endpoints. Locomotion behaviors could be significantly decreased by exposure to 4-nm and 10-nm TiO(2)-NPs at concentration of 1 ng/L in nematodes. Among genes required for the control of oxidative stress, only the expression patterns of sod-2 and sod-3 genes encoding Mn-SODs in animals exposed to small sizes of TiO(2)-NPs were significantly different from those in animals exposed to large sizes of TiO(2)-NPs. sod-2 and sod-3 gene expressions were closely correlated with lethality, growth, reproduction, locomotion behavior, intestinal autofluorescence, and ROS production in TiO(2)-NPs-exposed animals. Ectopically expression of human and nematode Mn-SODs genes effectively prevented the induction of ROS production and the development of toxicity of TiO(2)-NPs. Therefore, the altered expression patterns of Mn-SODs may explain the toxicity formation for different sizes of TiO(2)-NPs at predicted environmental relevant concentrations. In addition, we demonstrated here a strategy to investigate the toxicological effects of exposure to NPs upon humans by generating transgenic strains in nematodes for specific human genes.     

微生物源抗植物病毒物质及其抗病毒机理的研究进展

微生物代谢产生的有抗病毒作用的活性物质,具有内吸活性强、安全高效的优点.目前从微生物资源中筛选并获得抗植物病毒物质已经成为研究的热点,对微生物抗病毒物质的分离提取和抗病机理方面的研究已经取得了一定的进展.对来源于不同种类微生物的抗病毒活性物质,以及抗病机理作了论述,并对微生物源抗植物病毒物质研究进行了展望.     

A novel <Emphasis Type="SmallCaps">l</Emphasis>-aspartate dehydrogenase from the mesophilic bacterium <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> PAO1: molecular characterization and application for <Emphasis Type="SmallCaps">l</Emphasis>-aspartate production

l-aspartate dehydrogenase (EC 1.4.1.21; l-AspDH) is a rare member of amino acid dehydrogenase superfamily and so far, two thermophilic enzymes have been reported. In our study, an ORF PA3505 encoding for a putative l-AspDH in the mesophilic bacterium Pseudomonas aeruginosa PAO1 was identified, cloned, and overexpressed in Escherichia coli. The homogeneously purified enzyme (PaeAspDH) was a dimeric protein with a molecular mass of about 28 kDa exhibiting a very high specific activity for l-aspartate (l-Asp) and oxaloacetate (OAA) of 127 and 147 U mg⁻¹, respectively. The enzyme was capable of utilizing both nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) as coenzyme. PaeAspDH showed a T _m value of 48°C for 20 min that was improved to approximately 60°C by the addition of 0.4 M NaCl or 30% glycerol. The apparent K _m values for OAA, NADH, and ammonia were 2.12, 0.045, and 10.1 mM, respectively; comparable results were observed with NADPH. The l-Asp production system B consisting of PaeAspDH, Bacillus subtilis malate dehydrogenase and E. coli fumarase, achieved a high level of l-Asp production (625 mM) from fumarate in fed-batch process with a molar conversion yield of 89.4%. Furthermore, the fermentative production system C released 33 mM of l-Asp after 50 h by using succinate as carbon source. This study represented an extensive characterization of the mesophilic AspDH and its potential applicability for efficient and attractive production of l-Asp. Our novel production systems are also hopeful for developing the new processes for other compounds production.     

Competition between toxic Microcystis aeruginosa and nontoxic Microcystis wesenbergii with Anabaena PCC7120

To elucidate the changes in the proportions of microcystin (MC)-producing Microcystis, non-MC-producing Microcystis and Anabaena strains during cyanobacteria blooms, we compared their fitness under different initial biomass ratios. Culture experiments were carried out with three cyanobacterial strains: single-celled toxic Microcystis aeruginosa PCC7806 (Ma7806), single-celled nontoxic Microcystis wesenbergii FACHB-929 (Mw929) and filamentous Anabaena PCC7120 (An7120). Growth curves expressed as biovolume, Ma7806 microcystin-LR (MC-LR) content (detected with HPLC and ELISA), and the culture medium dissolved total nitrogen and dissolved total phosphorous (DTP) were measured to monitor nutrient uptake. Results suggest that the dominant strain in competition experiments between Ma7806 and An7120 was mainly controlled by the initial biomass ratio of the two strains, but there was also evidence for allelopathic interactions, where MC-LR produced by Ma7806 played an important role in the competition process. However, Mw929 was always less competitive when co-cultured with An7120 regardless of initial biomass ratio. Culture medium DTP showed significant differences between competition experiments in all sets, suggesting that Mw929 could be more suited to low phosphorus environments than Ma7806 and An7120. Overall, the competitive ability of Ma7806 was stronger than Mw929 when co-cultured with An7120 in the case of excess nutrients and the results could well unravel the seasonal succession process of cyanobacteria blooms.     

HAMLET binding to α-actinin facilitates tumor cell detachment

Cell adhesion is tightly regulated by specific molecular interactions and detachment from the extracellular matrix modifies proliferation and survival. HAMLET (Human Alpha-lactalbumin Made LEthal to Tumor cells) is a protein-lipid complex with tumoricidal activity that also triggers tumor cell detachment in vitro and in vivo, suggesting that molecular interactions defining detachment are perturbed in cancer cells. To identify such interactions, cell membrane extracts were used in Far-western blots and HAMLET was shown to bind α-actinins; major F-actin cross-linking proteins and focal adhesion constituents. Synthetic peptide mapping revealed that HAMLET binds to the N-terminal actin-binding domain as well as the integrin-binding domain of α-actinin-4. By co-immunoprecipitation of extracts from HAMLET-treated cancer cells, an interaction with α-actinin-1 and -4 was observed. Inhibition of α-actinin-1 and α-actinin-4 expression by siRNA transfection increased detachment, while α-actinin-4-GFP over-expression significantly delayed rounding up and detachment of tumor cells in response to HAMLET. In response to HAMLET, adherent tumor cells rounded up and detached, suggesting a loss of the actin cytoskeletal organization. These changes were accompanied by a reduction in β1 integrin staining and a decrease in FAK and ERK1/2 phosphorylation, consistent with a disruption of integrin-dependent cell adhesion signaling. Detachment per se did not increase cell death during the 22 hour experimental period, regardless of α-actinin-4 and α-actinin-1 expression levels but adherent cells with low α-actinin levels showed increased death in response to HAMLET. The results suggest that the interaction between HAMLET and α-actinins promotes tumor cell detachment. As α-actinins also associate with signaling molecules, cytoplasmic domains of transmembrane receptors and ion channels, additional α-actinin-dependent mechanisms are discussed.     

Conversion of a heme-based oxygen sensor to a heme oxygenase by hydrogen sulfide: effects of mutations in the heme distal side of a heme-based oxygen sensor phosphodiesterase (Ec DOS)

The heme-based oxygen-sensor phosphodiesterase from Escherichia coli (Ec DOS), is composed of an N-terminal heme-bound oxygen sensing domain and a C-terminal catalytic domain. Oxygen (O₂) binding to the heme Fe(II) complex in Ec DOS substantially enhances catalysis. Addition of hydrogen sulfide (H₂S) to the heme Fe(III) complex in Ec DOS also remarkably stimulates catalysis in part due to the heme Fe(III)–SH and heme Fe(II)–O₂ complexes formed by H₂S. In this study, we examined the roles of the heme distal amino acids, M95 (the axial ligand of the heme Fe(II) complex) and R97 (the O₂ binding site in the heme Fe(II)–O₂ complex) of the isolated heme-binding domain of Ec DOS (Ec DOS-PAS) in the binding of H₂S under aerobic conditions. Interestingly, R97A and R97I mutant proteins formed an oxygen-incorporated modified heme, verdoheme, following addition of H₂S combined with H₂O₂ generated by the reactions. Time-dependent mass spectroscopic data corroborated the findings. In contrast, H₂S did not interact with the heme Fe(III) complex of M95H and R97E mutants. Thus, M95 and/or R97 on the heme distal side in Ec DOS-PAS significantly contribute to the interaction of H₂S with the Fe(III) heme complex and also to the modification of the heme Fe(III) complex with reactive oxygen species. Importantly, mutations of the O₂ binding site of the heme protein converted its function from oxygen sensor to that of a heme oxygenase. This study establishes the novel role of H₂S in modifying the heme iron complex to form verdoheme with the aid of reactive oxygen species.