动物的起源和寒武纪大爆发:来自中国的化石证据

近30年来,中国埃迪卡拉纪—寒武纪发现了包括瓮安生物群和澄江动物群在内一系列重要化石群,为揭示动物的起源和寒武纪大爆发过程提供了全球独一无二的古生物学证据。文中全面而简洁地介绍发现于华南埃迪卡拉纪—寒武纪的所有化石群和重要动物化石发现,总结其中特异化石群保存类型和埋藏环境。其中,陡山沱型磷酸盐化胚胎化石群、庙河型宏体碳质膜化石群和牛蹄塘型海绵动物群,以及陡山沱组硅化的动物休眠胚胎化石和宽川铺动物群中"rsten"型化石均是全球这一时期华南独有的特异埋藏化石群。从时空两方面对化石群进行综合分析认为,动物可靠的最早化石记录发现于埃迪卡拉纪早期,成冰纪及其以前的动物化石均存在疑问。动物的起源和寒武纪大爆发经历了从浅水逐步向深水迁移,以及阶段性辐射和灭绝的过程。首先动物经历了在埃迪卡拉纪早期的隐形微体动物早期演化阶段,之后经过以埃迪卡拉型生物为代表的大型复杂化演化阶段,在寒武纪初期发生以梅树村动物群为代表的两侧对称动物和生物骨骼矿化的大爆发,并随后又被以澄江动物群为代表的寒武纪动物群所替代,在筇竹寺期达到了动物造型和生态系统复杂化的高峰。     

贵州江口桃映埃迪卡拉系陡山沱组中的三叶脊动物化石

本文描述的三叶脊类化石于2004年采自贵州东北部江口县桃映镇翁会村埃迪卡拉系陡山沱组上部庙河生物群,共2新属2新种:中国三射盘(新属新种)Triactindiscus sinensisgen.et sp.nov.及不规则似三角形盘(新属新种)Quasitriagondiscus irregularisgen.et sp.nov.。前者为大型盘状化石,具有3个呈碳质薄膜的长三角形叶脊,自盘体中央向边缘呈三辐射伸展,没有其它生物构造;后者为小型盘状化石,3条不规则叶脊在盘体中部形成似三角形并以此不同于其它三叶脊化石。庙河生物群2个三叶脊化石属相似于俄罗斯白海生物群的Albumares,Anfesta,Tribrachidium和澳大利亚埃迪卡拉生物群中的Tribrachidium,它们细节上有差异,但均属于埃迪卡拉系中三辐射对称的三叶动物。新的发现表明三叶动物在埃迪卡拉纪广泛分布于全球各地,也显示埃迪卡拉纪生物分异度比较高,辐射、两侧及三侧对称的动物均匀代表。贵州东北部江口桃映翁会庙河生物群含有丰富的宏观藻类及动物化石,如Protoconites,Cucullus,Sinospongia,Eoandromeda octobrachiata及新发现的2属三叶脊动物化石。江口庙河生物群组成上很相似峡东庙河生物群,也都位于陡山沱组上部黑色页岩中。江口庙河生物群不仅是整个庙河生物群的重要组成部分,也是埃迪卡拉纪生物演化的重要窗口。     

贵州埃迪卡拉纪瓮安生物群化石含量的统计分析

贵州瓮安埃迪卡拉纪陡山沱组（635-551Ma）上磷矿段保存了大量精美的磷酸盐化微体球粒化石,它们主要由多细胞藻类、疑源类和处于不同发育阶段的多种动物胚胎化石组成,此外还包括少量后生动物的幼、成体化石。本文以贵州瓮福磷矿陡山沱组上磷矿段灰白色球粒状白云质磷块岩为研究对象,在总结瓮安生物群中不同生物化石的鉴别特征基础上,定量统计采自该层位的两组岩石样品（WA—I和WA-r1）的酸处理砂样中的所有化石。统计结果表明,瓮安陡山沱组该磷块岩中化石质量和岩石中磷酸盐组分质量成正线性相关,两个样品中化石占全部磷酸盐组分的质量百分比均在10％左右,其中多细胞藻类和疑源类化石占全部化石含量均少于10％。这一结果客观地反映了瓮安生物群的化石丰度,证实了保存在瓮安陡山沱组上磷矿段灰色富氧含磷埋藏相中的瓮安生物群主要由动物胚胎化石组成的特征。     

湖北峡东地区九龙湾剖面震旦系陡山沱组微体化石的新发现

中国南方扬子地台震旦系陡山沱组产出丰富的微体化石,它们主要保存在磷块岩以及燧石结核和条带中。文章详细报道湖北峡东地区九龙湾剖面震旦系陡山沱组微体化石,描述以前未曾在峡东地区碳酸盐相燧石中发现的8属8种微体化石。研究九龙湾剖面陡山沱组大型带刺疑源类、微体多细胞藻类和动物胚胎化石的分布特征,发现Tianzhushania spinosa是最早出现的大型带刺疑源类分子,大冰期后微体生物的辐射是一个阶段性渐进的过程。同时．本项研究进一步证实华南扬子区陡山沱组碳酸盐相燧石和磷块岩地层中保存的微体化石面貌基本一致。     

湖北宜昌樟村坪埃迪卡拉纪陡山沱组磷酸盐化微体化石组合

保存于华南新元古代晚期陡山沱组中的磷酸盐化化石被认为与后生动物起源、真核生物演化有重要联系。位于鄂西黄陵隆起北缘的樟村坪地区,是华南最重要的工业磷矿产地之一,主要磷矿层属于埃迪卡拉纪地层,却鲜有磷块岩化石报道。此次研究利用钻孔样品的大量连续切片,在陡山沱组磷矿层中发现了丰富的保存精美的微体化石,化石组合包括可能的动物胚胎化石Megasphaera inornata;大型具刺疑源类Appendisphaerasp.,Cymatiosphaeroides kullingii,Dicrospinasphaera sp.,Ericiasphaera magna,Weissiella sp.;多细胞藻类Wengania globosa,W.exquisite,Sarcinophycus papilloformis,Thallophyca sp.,以及球状丝状蓝藻化石Archaeophycus yunnanensis,Cyanonema majus,Salome nunavutensis,Obruchevella minor,Siphonophycus kestron,S.typicum,S.robustum,S.septatum。这些微体化石的发现丰富了该区磷酸盐化化石资料,同时该化石组合面貌与黔中地区陡山沱组上磷块岩"瓮安生物群"以及峡东陡山沱组典型硅化生物群都具有相似性,化石层位的探讨也为华南不同沉积相区陡山沱组的地层对比提供了新的参考依据。     

扬子区晚震旦世动物化石新材料

扬子区晚震旦世地层中已有多种类型的动物及遗迹化石的报道。文中补充了不同地区和层位的骨骼及遗迹化石新材料,包括：江西上饶王家院陡山沱组顶部磷块岩中的磷酸盐化“十”字形骨针和云南晋宁王家湾灯影组上段隧石条带中的单轴双射硅质骨针,它们可能分属于钙质海绵和普通海绵类;贵州瓮安陡山沱组上段磷质白云岩中的可疑壳状化石;宜昌三斗坪金瓜墩陡山沱组下部（第二段）遗迹化石;瓮安陡山沱组上段及湖北南漳灯影组上段底部磷质硬底中的生物扰动构造。另外还报道了贵州清镇桃子冲剖面桃子冲组最底部的瓶状动物（Pro-tolagena limbata）化石,并认定桃子冲组与灯影组之间为假整合接触,其底界并无跨入震旦系的证据。     

论陡山沱组的年代

三峡地区震旦系的三层式地层结构 (冰积层 ,陡山沱组特色的大型带刺疑源类组合层 ,埃迪卡拉生物化石层 )在世界其它地区是常见的。通过生物和化学地层对比我们认为陡山沱组及其化石组合层是在马雷诺恩 ( Marinoan)冰期之后、埃迪卡拉生物群分异之前沉积的。根据这一地层对比方案以及西伯利亚、纳米比亚和阿瓦龙半岛 ( Avalon Peninsula)新元古代地层的精确放射性同位素测年资料 ,陡山沱组的沉积年龄很可能在五亿五千万年至六亿年之间。这一估计要新于以前发表的铷锶法或钾氩法测定的陡山沱组黑色页岩或海绿石年龄。更精确地估算陡山沱组的沉积年龄还有待于在陡山沱组地层中发现火山灰以及对火山灰的精确年龄测定 ,但我们根据地层对比估算的陡山沱组年龄 ,为评估庙河和瓮安陡山沱组生物群的演化意义提供了必要的地层框架。     

湖北保康陡山沱组磷酸盐化微体化石组合

中国南方震旦系陡山沱组磷块岩、燧石和页岩中陆续发现的精美保存的化石生物群,为我们提供了一个栩栩如生的新元古代晚期生物演化的图景,表明多细胞真核生物在新元古代冰期之后发生了非常显著的分异。其中磷块岩化石库以生物细胞结构的完好保存而著称。继在贵州瓮安、陕西勉县茶店和江西上饶朝阳之后,湖北保康白竹磷矿陡山沱组磷块岩中也发现了类似的磷酸盐化化石生物群。保康化石组合中包括多细胞藻类Wengania,Paramecia和原地保存的Thallophyca;大型复杂疑源类Meghystrichosphaeridium,Echinosphaeridium和目前仅在保康发现的Bacatisphaera;球状蓝菌化石Archaeophycus,丝状蓝菌化石Siphonophycus和在陡山沱组磷块岩中首次发现的Obruchevella;同时,内部保存不同数量小球体的球状化石在保康也大量产出。古地理分析表明中国南方扬子地台陡山沱组磷块岩中保存的磷酸盐化化石库大都形成于浅水台地边缘地带。     

新元古代磷酸盐化外包型腔原肠胚化石在瓮安生物群中的发现

贵州瓮安埃迪卡拉纪陡山沱组(635—551Ma)上磷矿段保存了丰富的磷酸盐化动物胚胎化石,其中绝大多数为早期卵裂胚胎化石,原肠胚化石相对罕见。文中报道瓮安生物群中新发现的一种类似现代两栖动物胚胎的外包型腔原肠胚化石,并依据新的三维立体胚胎化石标本对瓮安陡山沱组原肠胚期动物化石的多样性及其可能的亲缘关系进行初步探讨,认为:1)"外包型腔原肠胚"和已有轴性分化的"外包型实体原肠胚"的发现为证明瓮安生物群中存在两侧对称动物提供了新的化石证据;2)"单极内陷型腔原肠胚"因胚体存在巨大空腔(囊胚腔和原肠腔)而难以被磷酸盐化精细保存,故在瓮安生物群中的化石记录稀少且亲缘关系不明;3)瓮安生物群中的"单极内移型腔原肠胚"和"分层型腔原肠胚"化石的可靠性尚有待更多的标本提供佐证。瓮安生物群中颇具多样性的原肠胚期动物化石为探索后生动物在晚新元古代的胚胎发育模式开拓了思路。     

湖北宜昌埃迪卡拉系陡山沱组天柱山卵囊胞——Tianzhushania的新认识

我国南方陡山沱组的渗透矿化微体化石为认识埃迪卡拉动物辐射前的生物多样性,提供了异乎寻常的窗口;其中包括一些被视为早期动物胚胎的磷酸盐化球形化石。但是,一些学者将之与现生Thiomargarita sp．比较,把陡山沱组胚胎解释为巨大氧化硫细菌。湖北宜昌晓峰河剖面陡山沱组中发现Tianzhushania的大型具刺疑源类的膜壳中显示有1、2、4、8、16乃至数百个卵裂细胞标本,表明它们应是真核生物,很可能是在滞育卵囊胞中保存的早期卵裂的动物胚胎。此有力地论证了我国南方埃迪卡拉纪陡山沱组动物胚胎化石的保存,并将动物化石记录推前至632Ma前。为了区别Tianzhushania的已知形态种,新建Tianzhushania fissura sp．nov．和Tianzhushania confrerta sp．nov．两个新种,它们分别以含有不同数量卵裂细胞为特征。它们在陡山沱组中、上部的集中保存,可能与海平面变化或其它地质事件密切相关。而这需要更多有效年代地层资料加以合理解释。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.