Rock paper scissors: CRISPR/Cas9-mediated interference with geminiviruses in plants

<正>Geminiviruses are a group of circular single-stranded DNA viruses that constitute the largest family of plant viruses.Many diseases resulting from geminivirus infections, such as maize streak disease, cassava mosaic disease, tomato yellow leaf curl disease and cotton leaf curl diseases, cause significant problems in terms of economic losses, posing a serious threat to global crop productivity (Hanley-Bowdoin et al., 2013; Yang et al., 2019). As obligate intracellular     

Genome‐wide scans to detect positive selection in Large White and Tongcheng pigs

Due to the direction, intensity, duration and consistency of genetic selection, especially recent artificial selection, the production performance of domestic pigs has been greatly changed. Therefore, we reasoned that there must be footprints or selection signatures that had been left during domestication. In this study, with porcine 60K BeadChip genotyping data from both commercial Large White and local Chinese Tongcheng pigs, we calculated the extended haplotype homozygosity values of the two breeds using the long‐range haplotype method to detect selection signatures. We found 34 candidate regions, including 61 known genes, from Large White pigs and 25 regions comprising 57 known genes from Tongcheng pigs. Many selection signatures were found on SSC1, SSC4, SSC7 and SSC14 regions in both populations. According to quantitative trait loci and network pathway analyses, most of the regions and genes were linked to growth, reproduction and immune responses. In addition, the average genetic differentiation coefficient F_ST was 0.254, which means that there had already been a significant differentiation between the breeds. The findings from this study can contribute to further research on molecular mechanisms of pig evolution and domestication and also provide valuable references for improvement of their breeding and cultivation.     

林下植被和凋落物对寒温带森林生长季土壤CH4通量的影响

为进一步探究林下植被和凋落物管理对我国寒温带森林生长季土壤CH₄通量的影响,采用静态箱-气相色谱法对大兴安岭北部4种林型（白桦林、山杨林、樟子松林和兴安落叶松林）4种处理（自然状态、去除凋落物、去除林下植被以及去除林下植被和凋落物）的土壤CH₄通量排放特征进行观测研究。结果表明：该地区森林生长季土壤均表现为CH₄的汇,4种林型不同处理后土壤CH₄通量表现为单峰变化趋势,吸收峰值出现在7月或8月。自然状态4种林型土壤CH₄平均吸收通量表现为白桦林（-79.23±14.92）μg m^-2 h^-1>山杨林（-64.27±9.60）μg m^-2 h^-1>樟子松林（-62.54±15.48）μg m^-2 h^-1>兴安落叶松林（-48.73±12.26）μg m^-2 h^-1,兴安落叶松土壤CH₄平均吸收通量显著小于其他三种林型（P<0.05）。相比于自然状态,4种林型在去除凋落物后土壤CH₄吸收通量提高了2.12%-12.15%,但变化幅度均没有达到显著水平（P>0.05）。去除林下植被后4种林型CH₄吸收通量提高了0.84%-20.55%,且只有山杨林吸收增加达到显著水平（P<0.05）。同时去除林下植被和凋落物后,对白桦林和樟子松土壤CH₄通量影响不显著（P>0.05）,但对山杨林和兴安落叶松林影响显著（P<0.05）。总之,去除凋落物或林下植被均会提高土壤对CH₄吸收,去除林下植被对土壤CH₄通量的影响要大于去除凋落物的影响,但不同林型不同处理之间还存在差异。     

The microalga Parachlorella kessleri––A novel highly efficient lipid producer

The alga Parachlorella kessleri, strain CCALA 255, grown under optimal conditions, is characterized by storage of energy in the form of starch rather than lipids. If grown in the complete medium, the cultures grew rapidly, producing large amounts of biomass in a relatively short time. The cells, however, contained negligible lipid reserves (1–10% of DW). Treatments inducing hyperproduction of storage lipids in P. kessleri biomass were described. The cultures were grown in the absence or fivefold decreased concentration of either nitrogen or phosphorus or sulfur. Limitation by all elements using fivefold or 10‐fold diluted mineral medium was also tested. Limitation with any macroelement (nitrogen, sulfur, or phosphorus) led to an increase in the amount of lipids; nitrogen limitation was the most effective. Diluted nutrient media (5‐ or 10‐fold) were identified as the best method to stimulate lipid overproduction (60% of DW). The strategy for lipid overproduction consists of the fast growth of P. kessleri culture grown in the complete medium to produce sufficient biomass (DW more than 10 g/L) followed by the dilution of nutrient medium to stop growth and cell division by limitation of all elements, leading to induction of lipid production and accumulation up to 60% DW. Cultivation conditions necessary for maximizing lipid content in P. kessleri biomass generated in a scale‐up solar open thin‐layer photobioreactor were described. Biotechnol. Bioeng. 2013; 110: 97–107. © 2012 Wiley Periodicals, Inc.     

噬菌体与宿主菌间的角逐

噬菌体和它们的宿主菌组成了地球上教目最庞大的微生物种群,噬菌体靠寄生宿主菌来扩增繁衍。但在漫长的进化中,噬菌体与宿主菌间不单是捕食关系,它们间还形成了复杂的相互对抗机制,其中抵抗防御机制的抗防御机制也会促使抗．抗防御机制的产生。从生态学角度来看,噬菌体和宿主菌间的共进化保持着动态平衡。本文综述近年来这一领域的研究,为更清楚地了解噬菌体与宿主菌间的关系和应用提供了参考。     

过氧化氢预处理增强敏感型黑豆抗铝能力的生理机制

以铝敏感型黑豆(简称SB)幼苗为实验材料,在水培条件下进行不同浓度过氧化氢(H2O2)和AlCl3处理,考察其生长和相关生理指标变化,探讨H2 O2预处理缓解黑豆铝毒害的生理以及分子机理.结果显示:(1)黑豆幼苗根的相对生长量在0.1和1.0 μmol·L-1 H2O2处理下始终得到显著促进,并以后者效果更好,而在10.0和100.0 μmol·L1 H2O2处理下先表现促进后受到显著抑制.(2)经过1.0 μmol·L-1 H2O2预处理的SB幼苗在不同程度Al3+胁迫(50～400 μmol·L 1)3周后,其叶片和根中总蛋白含量分别显著增加了16.7％～41.2％和10.0％～25.0％,MDA含量减少了近50％;而其同期的SOD和POD活性显著增加.(3) H2 O2预处理可诱导SB根和叶中的SOD基因(Mg/Fe-SOD和Mn-SOD)的表达水平明显提高.研究表明,低浓度H2O2能显著促进铝胁迫下铝敏感型黑豆幼苗生长,且主要是通过增加植株抗氧化酶活性和相关基因表达水平来提高其对铝胁迫的抗性.     

Tryptase Promotes Atherosclerotic Plaque Haemorrhage in ApoE-/- Mice

Tryptase, the most abundant mast cell (MC) granule protein, plays an important role in atherosclerosis plaque development. To test the hypothesis that tryptase participates directly in atherosclerosis plaque haemorrhage, the gene sequence and siRNA for tryptase were cloned into a lentivirus carrier and atherosclerosis plaque haemorrhage models in ApoE-/- mice were constructed. After a cuffing-cervical artery operation, the mice were randomly divided into 6 groups. Hematoxylin and eosin(HE) staining showed that the cervical artery plaque area was much larger in the tryptase overexpression group compared to the other groups, and there was greater artery stenosis. The artery stenosis from the cuff-side in all groups was more than 90%, except the siRNA group. Tryptase promotes plaque haemorrhage distinctively because 50% of the mice in the tryptase overexpression group had plaque haemorrhage, while only 10% in the siRNA group did. The immunohistochemistry of the cervical artery plaque showed that plasminogen activator inhibitor-1 (PAI-1) expression was the lowest while tissue plasminogen activator (tPA), CD31, CD34 and VEGF was the highest in the tryptase overexpression groups. This observation was completely contrary to what was observed in the siRNA group. Tryptase promoted bEnd.3 cell growth, migration and capillary-like tube formation, which suggests that tryptase can promote microvessel angiogenesis. PAI-1 expression was inhibited, while tPA expression was increased by tryptase in bEnd.3 cells. Our in vivo and in vitro studies suggest that trypase can promote atherosclerotic plaque haemorrhage by promoting angiogenesis and regulating the balance of PAI-1 and tPA. Thus, regulating tryptase expression in MCs may provide a potential target for atherosclerosis treatment.