桑蚕金属硫蛋白基因在大肠杆菌中的克隆和表达

用\%Bam\%HⅠ和\%Sac\%Ⅰ双酶切质粒pCM1\|1,获得酵母的MTI基因片段,用非放射性地高辛标记作为探针。提取桑蚕肥苏蚕卵的总DNA,分别用\%Eco\%RⅠ、\%Bam\%HⅠ和\%Hin\%dⅢ酶切,与MTI探针进行Southern杂交,出现较强的杂交信号。然后用\%Eco\%RⅠ完全酶切桑吞的总DNA,电洗脱法回收1～6kb的染色体片断,与\%Eco\%RⅠ酶切的M13-载体以3∶1比例连接,转化受体菌DH5α。筛选到4 000多个白色转化子,与探针MTI进行Southern杂交筛选阳性转化子,选择到有强杂交信号的三个转化子［编号为T1(pZHC\|1)\,T5(pZHC\|5)\,T7(pZHC\|7)\]。用12种限制性内切酶对pZHC\|5重组质粒进行酶切分析表明插入片段约12kb,在基因内有一个\%Hin\%dⅢ位点。抗性测定表明受体菌DH5α在含有50mmol/L CuSO\-4的培养基上生长,在含有52mmol/L CuSO\-4的培养基上不生长,而转化子确能在含有52mmol/L CuSO\-4以上的培养基上生长。上述研究结果表明12kb左右的插入片段含有桑吞的金属硫蛋白基因。     

HIV Nef-mediated CD4 down-regulation is adaptor protein complex 2 dependent

Nef is a crucial viral protein for HIV to replicate at high titers and in the development of AIDS. One Nef function is down-regulating CD4 from the cell surface, which correlates with Nef-enhanced viral pathogenicity. Nef down-regulates CD4 by linking CD4 to clathrin-coated pits. However, the mechanistic connection between the C-terminal dileucine motif of Nef and the component(s) of the clathrin-coated pits has not been pinpointed. In this report we used two AP-2 complex-specific inhibitors: a dominant negative mutant of Eps15 (Eps15DIII) that binds to the alpha subunit of AP-2 complex and a small interference RNA that is specific for the mu2 subunit of AP-2 complex. We show that both HIV Nef- and SIV Nef-mediated CD4 down-regulations were profoundly blocked by the synergistic effect of Eps15DIII and RNA interference of AP-2 expression. The results demonstrate that HIV/SIV Nef-mediated CD4 down-regulation is AP-2 dependent. We also show that the PMA-induced CD4 down-regulation was blocked by these two inhibitors. Therefore, PMA-induced CD4 down-regulation is also AP-2 dependent. The results demonstrate that, like the tyrosine sorting motif-dependent endocytosis (for which the transferrin receptor and the epidermal growth factor receptor are the two prototypes), dileucine sorting motif-dependent endocytosis of Nef and CD4 are also AP-2 dependent.     

T-box genes coordinate regional rates of proliferation and regional specification during cardiogenesis

Mutations in T-box genes are the cause of several congenital diseases and are implicated in cancer. Tbx20-null mice exhibit severely hypoplastic hearts and express Tbx2, which is normally restricted to outflow tract and atrioventricular canal, throughout the heart. Tbx20 mutant hearts closely resemble those seen in mice overexpressing Tbx2 in myocardium, suggesting that upregulation of Tbx2 can largely account for the cardiac phenotype in Tbx20-null mice. We provide evidence that Tbx2 is a direct target for repression by Tbx20 in developing heart. We have also found that Tbx2 directly binds to the Nmyc1 promoter in developing heart, and can repress expression of the Nmyc1 promoter in transient transfection studies. Repression of Nmyc1 (N-myc) by aberrantly regulated Tbx2 can account in part for the observed cardiac hypoplasia in Tbx20 mutants. Nmyc1 is required for growth and development of multiple organs, including the heart, and overexpression of Nmyc1 is associated with childhood tumors. Despite its clinical relevance, the factors that regulate Nmyc1 expression during development are unknown. Our data present a paradigm by which T-box proteins regulate regional differences in Nmyc1 expression and proliferation to effect organ morphogenesis. We present a model whereby Tbx2 directly represses Nmyc1 in outflow tract and atrioventricular canal of the developing heart, resulting in relatively low proliferation. In chamber myocardium, Tbx20 represses Tbx2, preventing repression of Nmyc1 and resulting in relatively high proliferation. In addition to its role in regulating regional proliferation, we have found that Tbx20 regulates expression of a number of genes that specify regional identity within the heart, thereby coordinating these two important aspects of organ development.     

Variation between freshwater and terrestrial fungal communities on decaying bamboo culms

Fungal communities on decaying culms of a bamboo host (Phyllostachys bambusoides) from freshwater and adjacent terrestrial habitats were identified. Collections were made at Xiao Bai Long Mountain, Yiliang, Yunnan, China in the winter and summer. In each collection, 100 similar-sized bamboo culms were collected, comprising 50 submerged samples from a stream and 50 terrestrial samples from adjacent riparian vegetation. A total of 82 fungal taxa were recorded from the samples, including 30 ascomycetes and 52 anamorphic fungi. The frequency of occurrence of these fungi were recorded and the Shannon–Weiner indices (H′) were applied to evaluate fungal diversity. The results showed that variation of the fungal diversity between the summer and winter collections was insignificant (0.2<p<0.5). Fungal diversity on submerged bamboo however, was significantly higher than that on terrestrial bamboo (p<0.001). Further findings were that: (1) some commonly recorded freshwater and terrestrial taxa were found in both habitats, but overall there were only 15 overlapping species between the two habitats; (2) the dominant species in each habitat were considerably different, and (3) only a few fungi were dominant, while most species were rare, being recorded only once or twice. Factors responsible for the distribution patterns and variations in composition of the fungal communities are discussed.     

High-performance liquid chromatography coupled with tandem mass spectrometry applied for metabolic study of ginsenoside Rb1 on rat

Liquid chromatography coupled with mass spectrometry and tandem mass spectrometry has been applied to investigate the in vivo metabolism of ginsenoside Rb(1) in rat. Both positive electrospray ionization mass spectrometry and negative electrospray ionization mass spectrometry were used to identify the Rb(1) and its metabolites in rat plasma, urine, and feces samples. Oxygenation and deglycosylation were found to be the major metabolic pathways of Rb(1) in rat. A total of nine metabolites were detected in urine and feces samples collected after intravenous and oral administration. Deglycosylated metabolism of Rb(1) generated other ginsenosides as the major metabolites, such as Rd, Rg(3) or F(2), Rh(2), or C-K. This result indicates that the ginsenoside Rb(1) has many pharmacological activities and could be used as a prodrug.     

中国两栖动物受威胁现状评估

为了了解我国两栖动物受威胁现状和致危因素, 进而制定相关的保护措施和开展国际合作, 本文依据中国两栖动物野生种群与生境现状, 利用《IUCN物种红色名录濒危等级和标准》(3.1版)和《IUCN物种红色名录标准在国家或地区的应用指南》(4.0版), 对中国已知的408种两栖动物的濒危状况进行了评估, 并编制了《中国两栖动物红色名录》。评估结果表明: 中国两栖动物有1种灭绝, 1种区域灭绝, 受威胁的两栖动物共计176种, 占评估物种总数的43.1%, 明显高于《IUCN濒危物种红色名录》(2015)的物种受威胁率(30.8%)。中国两栖动物特有种272种, 其中48.9%属于受威胁物种。中国两栖动物受威胁比例最高的目是有尾目(63.4%), 明显高于无尾目(39.0%); 受威胁比例最高的科是隐鳃鲵科(Cryptobranchidae) (仅有1种, 100%受威胁), 小鲵科(Hynobiidae) (86.7%)和叉舌蛙科(Dicroglossidae) (78.1%)。有11个省区的受威胁物种数占本省区两栖动物物种总数的30%及以上, 前3位分别是四川(40.8%)、广西(39.2%)和云南(37%)。中国大多数两栖动物物种分布在西南山地和华南地区, 以海拔2,000 m以下区域为主。栖息地退化或丧失、捕捉、环境污染列受威胁两栖动物致危因子的前3位。鉴于中国两栖动物区系的复杂性和独特性, 进一步加强两栖动物资源调查、种群和生境监测及相关科学研究, 仍是今后一段时期开展两栖动物多样性保护和濒危物种拯救行动的关键性基础工作。     

High auxin stimulates callus through SDG8-mediated histone H3K36 methylation in Arabidopsis

Callus induction,which results in fate transition in plant cells,is considered as the first and key step for plant regeneration.This process can be stimulated in different tissues by a callus-inducing medium(CIM),which contains a high concentration of phytohormone auxin.Although a few key regulators for callus induction have been identified,the multiple aspects of the regulatory mechanism driven by high levels of auxin still need further investigation.Here,we find that high auxin induces callus ...     

Monophosphoryl lipid A alleviated radiation-induced testicular injury through TLR4-dependent exosomes

Radiation protection on male testis is an important task for ionizing radiation-related workers or people who receive radiotherapy for tumours near the testicle. In recent years, Toll-like receptors (TLRs), especially TLR4, have been widely studied as a radiation protection target. In this study, we detected that a low-toxicity TLR4 agonist monophosphoryl lipid A (MPLA) produced obvious radiation protection effects on mice testis. We found that MPLA effectively alleviated testis structure damage and cell apoptosis induced by ionizing radiation (IR). However, as the expression abundance differs a lot in distinct cells and tissues, MPLA seemed not to directly activate TLR4 singling pathway in mice testis. Here, we demonstrated a brand new mechanism for MPLA producing radiation protection effects on testis. We observed a significant activation of TLR4 pathway in macrophages after MPLA stimulation and identified significant changes in macrophage-derived exosomes protein expression. We proved that after MPLA treatment, macrophage-derived exosomes played an important role in testis radiation protection, and specially, G-CSF and MIP-2 in exosomes are the core molecules in this protection effect.     

Revealing the community and metabolic potential of active methanotrophs by targeted metagenomics in the Zoige wetland of the Tibetan Plateau

The Zoige wetland of the Tibetan Plateau is one of the largest alpine wetlands in the world and a major emission source of methane. Methane oxidation by methanotrophs can counteract the global warming effect of methane released in the wetlands. Understanding methanotroph activity, diversity and metabolism at the molecular level can guide the isolation of the uncultured microorganisms and inform strategy-making decisions and policies to counteract global warming in this unique ecosystem. Here we applied DNA stable isotope probing using ¹³C-labelled methane to label the genomes of active methanotrophs, examine the methane oxidation potential and recover metagenome-assembled genomes (MAGs) of active methanotrophs. We found that gammaproteobacteria of type I methanotrophs are responsible for methane oxidation in the wetland. We recovered two phylogenetically novel methanotroph MAGs distantly related to extant Methylobacter and Methylovulum. They belong to type I methanotrophs of gammaproteobacteria, contain both mxaF and xoxF types of methanol dehydrogenase coding genes, and participate in methane oxidation via H₄MPT and RuMP pathways. Overall, the community structure of active methanotrophs and their methanotrophic pathways revealed by DNA-SIP metagenomics and retrieved methanotroph MAGs highlight the importance of methanotrophs in suppressing methane emission in the wetland under the scenario of global warming.     

中国脊椎动物2020年新增物种

为了及时掌握中国脊椎动物新增物种情况, 本文系统检索和整理了2020年发表的分类学文献, 汇总结果表明: 2020年中国脊椎动物共新增109种, 其中新物种100种, 国家级新记录种9种。包括鱼类新种24种、两栖类新种41种和新记录4种、爬行类新种30种和新记录4种、鸟类新种1种、哺乳类新种4种和新记录1种。上述新增物种中有92种描述报道时应用了分子遗传学证据, 占新增物种数量的84.4%。在新增脊椎动物物种中, 两栖类集中于无尾目、爬行类全部属于有鳞目, 分别有43种和34种, 其累计占比超新增物种总数的70%。在云南、西藏、湖南、贵州、四川等省区发现新物种数量较多, 均有10种及以上, 累计占比超新增物种总数的60%。绝大部分物种为中国学者发表, 绝大多数论文发表于英文期刊。总结数据提示今后需持续加强我国低等脊椎动物多样性的调查研究, 重视运用分子系统学技术进行物种识别。