基于线粒体COI序列的DNA条形码在中国海口足类物种鉴定中的应用分析

中国海口足类动物区系具有丰富的物种多样性,是我国海洋底栖生物中的重要经济类群。口足类的属内种间鉴别特征有的极为相似,仅依靠传统的形态分类方法很难对近缘种和疑难种进行准确的鉴定。DNA条形码技术可以弥补传统形态学鉴定的某些局限,为物种鉴定提供了有效的工具。该研究探讨了利用线粒体COI序列对中国海口足类进行物种鉴定的可行性,共获得口足目4总科6科24属38个种的204条线粒体COI序列,与Gen Bank收录的14种42条口足类同源序列进行比对,结果显示口足类COI基因不存在碱基插入缺失现象,碱基组成偏倚明显,A+T含量(63.5%)显著高于G+C含量(36.5%)。基于Kimura双参数模型计算遗传距离,结果显示遗传距离随着分类阶元的增高而增大。同物种种内个体间的遗传距离变化范围在0%~3.91%,平均值为0.76%。同属内各物种间的遗传距离变化范围为6.55%~18.99%,平均值为12.91%。同科内不同属间的遗传距离变化范围为9.16%~23.32%,平均值为16.89%。不同科间的遗传距离变化范围为16.52%~26.6%,平均值为21.31%。由此可见,口足类COI基因的种间和种内遗传距离存在明显的间隙。基于COI序列构建的口足类邻接关系树显示所有包含大于1个个体的物种均可形成单系群,且节点支持率均为100%。本研究证明了COI序列作为DNA条形码标准基因在口足类物种鉴定中的有效性。此外,研究发现中国沿海分布的口虾蛄可能至少存在两个隐存种,实证了基于COI序列的DNA条形码技术能够用于口虾蛄隐存多样性的探究。     

国内外天然橡胶期现货价格波动关系研究

[目的]近年来,随着重要农产品保障战略的逐步实施,党和国家十分重视天然橡胶产业发展,天然橡胶等战略性农产品的供需形势及价格走势越来越受到社会各界的关注.尤其是新冠肺炎疫情暴发以来,构建国内国际双循环相互促进的新发展格局显得至关重要.天然橡胶作为国内重要的战略物资,期货市场发展日渐成熟,研究其国内外价格波动关系规律也就势...     

新疆金融发展与二元经济结构转换分析

分析了新疆的二元经济结构现状,并从整体金融发展和农村金融发展2个层面,对新疆金融发展和二元经济结构转化之间的关系进行了分析。结果表明：①新疆整体金融发展规模和二元经济结构转化正相关,但是两者之间不存在Granger意义上的因果关系;整体金融发展效率和二元经济结构转化正相关,并且前者是后者的Granger原因。②新疆农村金融发展规模和二元经济结构转化正相关,并且前者是后者Granger原因;农村金融发展效率和二元经济结构转化负相关,但是两者之间不存在Granger意义上的因果关系。并据此提出了相关的建议。     

物理学发现中灵感的特征与类型

通过对物理学发现的典型事例的分析，探讨了物理学发现中５种灵感特征及９种灵感思维的类型。     

cDNA文库在棉花基因发掘中的应用

构建cDNA文库是发掘基因和研究基因功能的重要工具,也是基因组学研究的重要技术手段。棉花作为世界上重要的经济作物之一,研究人员已经构建了大量的棉花cDNA文库,为棉花基因发掘和功能研究积累了丰富的Expressed Sequence Tags(ESTs)资源。本文对近几年来cDNA文库在棉花基因发掘中的应用进行了总结。     

反事实思维与因果推理的关系

反事实思维是人们日常生活中经常产生的一种思维方式 ,这种思维常常影响因果推理和归因。国外许多研究者对他们的关系以及影响因素和机制进行了研究。该文对这些研究成果与分歧进行综述 ,并提出了需要进一步探讨的问题     

农地确权的政策效果“事与愿违”吗?——基于农户异质性的因果效应评估

农地确权的政策效果及其对农户生计决策与福祉的影响,已有的实证研究看法不一。已有研究的一般假设是政策干预与农户对政策的响应是随机的,而我国的农地确权试点区域与试点时间均具有非随机的政策选择性,因而农户的应对决策并非随机。因此,已有研究的随机性假设需要加以检视。使用非参数匹配因果推断,全面估计农地确权对农户六类资源配置决策和福祉的影响,并分别从政策设计与实施的供给侧角度和农户面对政策变化调整其决策的需求侧角度,揭示已有实证研究结果不一致的原因。研究发现,在农业生产资料投入、劳动力向非农部门转移和获得正式贷款方面,确权政策的“顶层设计”与农户决策相匹配,有助于农户据此进行专业化分工与生产,政策效果虽然边际递减,但没有出现不一致现象。在土地流转方面,政策供给侧的选择偏差使农户流转土地的谈判交易成本上升33.3%,时间交易成本上升1.45倍;政策需求侧的农户应对行为使流转土地的谈判交易成本上升3.1倍,时间交易成本上升27.8%。供给侧与需求侧的双向偏差,加上确权的赋权增量非常有限,使政策效果与政策预期不一致,但这并不意味着确权是可有可无的,而是说明人们对确权效果的预期存在一定偏误。     

Jellyfish as an Alternative Source of Bioactive Antiproliferative Compounds

Jellyfish are commonly considered a nuisance for their negative effects on human activities (e.g., fisheries, power plants and tourism) and human health. However, jellyfish provide several benefits to humans and are commonly eaten in eastern countries. Additionally, recent studies have suggested that jellyfish may become a source of high-value molecules. In this study, we tested the effects of the methanolic extracts and enriched fractions, obtained by solid-phase extraction fractionation, from the scyphomedusae Pelagia noctiluca, Rhizostoma pulmo, Cotylorhiza tuberculata and the cubomedusa Caryddea marsupialis on different human cancer cell lines in order to evaluate a potential antiproliferative activity. Our results indicated that fraction C from Caryddea marsupialis-(CM) and C. tuberculata oral arms (CTOA) were the most active to reduce cell viability in a dose-dependent manner. LC/MS based dereplication analyses highlighted that both bioactive fractions contained mainly fatty acids and derivatives, with CM additionally containing small peptides (0.7–0.8 kDa), which might contribute to its higher biological activity. The mechanism of action behind the most active fraction was investigated using PCR arrays. Results showed that the fraction C of CM can reduce the expression of genes involved in apoptosis inhibition in melanoma-treated cells, which makes jellyfish a potential new source of antiproliferative drugs to be exploited in the future.     

Aerophobin-1 from the Marine Sponge Aplysina aerophoba Modulates Osteogenesis in Zebrafish Larvae

Longer life expectancy has led to an increase in efforts directed to the discovery of new healing agents for disorders related to aging, such as bone diseases. Harboring an incredible variety of bioactive metabolites, marine organisms are standing out as fruitful sources also in this therapeutic field. On the other hand, the in vivo zebrafish model has proven to be an excellent low-cost screening platform for the fast identification of molecules able to regulate bone development. By using zebrafish larvae as a mineralization model, we have thus evaluated the effects of the crude acetonic extract from the marine sponge Aplysina aerophoba and its bromotyrosine components on bone development. Obtained results led to the selection of aerophobin-1 (1) as a promising candidate for applications in regenerative medicine, paving the way for the development of a novel therapeutic option in osteoporosis treatment.     

Natural products as sources of herbicides: current status and future trends

Although natural product-based discovery strategies have not been as successful for herbicides as for other pesticides or pharmaceuticals, there have been some notable successes. Phosphinothricin, the biosynthetic version of glufosinate, and bialaphos are phytotoxic microbial products that have yielded commercial herbicides. Cinmethylin, a herbicidal analogue of cineole, has been sold in Europe and Asia. The triketone herbicides are derivatives of the plant-produced phytotoxin leptospermone. These products represent only a small fraction of commercialized herbicides, but they have each introduced a novel molecular target site for herbicides. Analysis of the literature reveals that phytotoxic natural products act on a large number of unexploited herbicide target sites. The pesticide industry's natural product discovery efforts have so far concentrated on microbially derived phytotoxins, primarily from non-pathogenic soil microbes, involving the screening of large numbers of exotic isolates. Plant pathogens usually produce potent phytotoxins, yet they have received relatively little attention. Even less effort has been made to discover plant-derived phytotoxins. Bioassay-directed isolation has been the preferred method of discovery after a producing organism is selected. This laborious approach often leads to rediscovery of known compounds. Modern tandem separation/chemical characterization instrumentation can eliminate much of this problem by identification of compounds before they are bioassayed.