Hydatellaceae are water lilies with gymnospermous tendencies

The flowering plant family Hydatellaceae was recently discovered to be allied to the ancient angiosperm lineage Nymphaeales (water lilies). Because of its critical phylogenetic position, members of the Hydatellaceae have the potential to provide insights into the origin and early diversification of angiosperms. Here I report that Hydatella expresses several rare embryological features that, in combination, are found only in members of the Nymphaeales. At maturity, the female gametophyte is four-celled, four-nucleate and will produce a diploid endosperm, as is characteristic of most early divergent angiosperm lineages. As with all members of the Nymphaeales, endosperm in Hydatella is minimally developed and perisperm is the major embryo-nourishing tissue within the seed. Remarkably, Hydatella exhibits a maternal seed-provisioning strategy that is unique among flowering plants, but common to all gymnosperms: pre-fertilization allocation of nutrients to the embryo-nourishing tissue. This exceptional case of pre-fertilization maternal provisioning of a seed in Hydatella may well be an apomorphic feature of Hydatellaceae alone but, given the newly discovered phylogenetic position of this family, potentially represents a plesiomorphic and transitional condition associated with the origin of flowering plants from gymnospermous ancestors.     

Fossil evidence of water lilies (Nymphaeales) in the Early Cretaceous

Phylogenetic analyses have identified the water lilies (Nymphaeales: Cabombaceae and Nymphaeaceae), together with four other small groups of flowering plants (the 'ANITA clades': Amborellaceae, Illiciales, Trimeniaceae, Austrobaileyaceae), as the first diverging lineages from the main branch of the angiosperm phylogenetic tree, but evidence of these groups in the earliest phases of the angiosperm fossil record has remained elusive. Here we report the earliest unequivocal evidence, based on fossil floral structures and associated pollen, of fossil plants related to members of the ANITA clades. This extends the history of the water lilies (Nymphaeales) back to the Early Cretaceous (125-115 million years) and into the oldest fossil assemblages that contain unequivocal angiosperm stamens and carpels. This discovery adds to the growing congruence between results from molecular-based analyses of relationships among angiosperms and the palaeobotanical record. It is also consistent with previous observations that the flowers of early angiosperms were generally very small compared with those of their living relatives.     

New frog family from India reveals an ancient biogeographical link with the Seychelles

About 96% of the more than 4,800 living anuran species belong to the Neobatrachia or advanced frogs. Because of the extremely poor representation of these animals in the Mesozoic fossil record, hypotheses on their early evolution have to rely largely on extant taxa. Here we report the discovery of a burrowing frog from India that is noticeably distinct from known taxa in all anuran families. Phylogenetic analyses of 2.8 kilobases of mitochondrial and nuclear DNA unambiguously designate this frog as the sister taxon of Sooglossidae, a family exclusively occurring on two granitic islands of the Seychelles archipelago. Furthermore, molecular clock analyses uncover the branch leading to both taxa as an ancient split in the crown-group Neobatrachia. Our discovery discloses a lineage that may have been more diverse on Indo-Madagascar in the Cretaceous period, but now only comprises four species on the Seychelles and a sole survivor in India. Because of its very distinct morphology and an inferred origin that is earlier than several neobatrachian families, we recognize this frog as a new family.     

Dating the origin of the Orchidaceae from a fossil orchid with its pollinator

Since the time of Darwin, evolutionary biologists have been fascinated by the spectacular adaptations to insect pollination exhibited by orchids. However, despite being the most diverse plant family on Earth, the Orchidaceae lack a definitive fossil record and thus many aspects of their evolutionary history remain obscure. Here we report an exquisitely preserved orchid pollinarium (of Meliorchis caribea gen. et sp. nov.) attached to the mesoscutellum of an extinct stingless bee, Proplebeia dominicana, recovered from Miocene amber in the Dominican Republic, that is 15-20 million years (Myr) old. This discovery constitutes both the first unambiguous fossil of Orchidaceae and an unprecedented direct fossil observation of a plant-pollinator interaction. By applying cladistic methods to a morphological character matrix, we resolve the phylogenetic position of M. caribea within the extant subtribe Goodyerinae (subfamily Orchidoideae). We use the ages of other fossil monocots and M. caribea to calibrate a molecular phylogenetic tree of the Orchidaceae. Our results indicate that the most recent common ancestor of extant orchids lived in the Late Cretaceous (76-84 Myr ago), and also suggest that the dramatic radiation of orchids began shortly after the mass extinctions at the K/T boundary. These results further support the hypothesis of an ancient origin for Orchidaceae.     

A basal troodontid from the Early Cretaceous of China

Troodontid dinosaurs form one of the most avian-like dinosaur groups. Their phylogenetic position is hotly debated, and they have been allied with almost all principal coelurosaurian lineages. Here we report a basal troodontid dinosaur, Sinovenator changii gen. et sp. nov., from the lower Yixian Formation of China. This taxon has several features that are not found in more derived troodontids, but that occur in dromaeosaurids and avialans. The discovery of Sinovenator and the examination of character distributions along the maniraptoran lineage indicate that principal structural modifications toward avians were acquired in the early stages of maniraptoran evolution.     

要善于发现美

<正>这是一个美好的夜晚。天空中没有云。月亮像一只小船。没有风,池塘水平如镜。一些睡莲漂浮在水面。青蛙们正在荷叶上唱歌。一只胖青蛙唱道:"我不开心。我不开心。这个池塘太平静。"一只瘦青蛙唱道:"我真开心。我真开心。池塘里有许多美景。"胖青蛙听了这首歌。他觉得奇怪:"美景在哪里?"他     

Human immunodeficiency viruses: SIV infection in wild gorillas

Chimpanzees (Pan troglodytes troglodytes) from west central Africa are recognized as the reservoir of simian immunodeficiency viruses (SIVcpzPtt) that have crossed at least twice to humans: this resulted in the AIDS pandemic (from human immunodeficiency virus HIV-1 group M) in one instance and infection of just a few individuals in Cameroon (by HIV-1 group N) in another. A third HIV-1 lineage (group O) from west central Africa also falls within the SIVcpzPtt radiation, but the primate reservoir of this virus has not been identified. Here we report the discovery of HIV-1 group O-like viruses in wild gorillas.     

The stability against freezing of an internal liquid-water ocean in Callisto

The discovery of the induced magnetic field of Callisto-one of Jupiter's moons-has been interpreted as evidence for a subsurface ocean, even though the presence of such an ocean is difficult to understand in the context of existing theoretical models. Tidal heating should not be significant for Callisto, and, in the absence of such heating, it is difficult to see how this internal ocean could have survived until today without freezing. Previous work indicated that an outer ice layer on the ocean would be unstable against solid-state convection, which once begun would lead to total freezing of liquid water in about 108 years. Here I show that when a methodology for more physically reasonable water ice viscosities (that is, stress-dependent non-newtonian viscosities, rather than the stress-independent newtonian viscosities considered previously) is adopted, the outer ice shell becomes stable against convection. This implies that a subsurface ocean could have survived up to the present, without the need for invoking antifreeze substances or other special conditions.     

陈介祺的金石学成就和历史地位

本文通过对陈介祺家世、时代背景、交游、收藏、考释、著述等方面的论述，意在表达陈氏在金石学领域内的贡献。具体分析论证了其对封泥、陶文的研究发现和开创之功，同时，对其藏古、鉴古、释古、传古的治学特点也进行了相关的价值判断，从而以推动学术界对陈介祺的重视和研究。     

A primitive fish close to the common ancestor of tetrapods and lungfish

The relationship of the three living groups of sarcopterygians or lobe-finned fish (tetrapods, lungfish and coelacanths) has been a matter of debate. Although opinions still differ, most recent phylogenies suggest that tetrapods are more closely related to lungfish than to coelacanths. However, no previously known fossil taxon exhibits a concrete character combination approximating the condition expected in the last common ancestor of tetrapods and lungfish -- and it is still poorly understood how early sarcopterygians diverged into the tetrapod lineage (Tetrapodomorpha) and the lungfish lineage (Dipnomorpha). Here we describe a fossil sarcopterygian fish, Styloichthys changae gen. et sp. nov., that possesses an eyestalk and which exhibits the character combination expected in a stem group close to the last common ancestor of tetrapods and lungfish. Styloichthys from the Lower Devonian of China bridges the morphological gap between stem-group sarcopterygians (Psarolepis and Achoania) and basal tetrapodomorphs/basal dipnomorphs. It provides information that will help in the study of the relationship of early sarcopterygians, and which will also help to resolve the tetrapod-lungfish divergence into a documented sequence of character acquisition.     

An inhibitor of Bcl-2 family proteins induces regression of solid tumours

Proteins in the Bcl-2 family are central regulators of programmed cell death, and members that inhibit apoptosis, such as Bcl-X(L) and Bcl-2, are overexpressed in many cancers and contribute to tumour initiation, progression and resistance to therapy. Bcl-X(L) expression correlates with chemo-resistance of tumour cell lines, and reductions in Bcl-2 increase sensitivity to anticancer drugs and enhance in vivo survival. The development of inhibitors of these proteins as potential anti-cancer therapeutics has been previously explored, but obtaining potent small-molecule inhibitors has proved difficult owing to the necessity of targeting a protein-protein interaction. Here, using nuclear magnetic resonance (NMR)-based screening, parallel synthesis and structure-based design, we have discovered ABT-737, a small-molecule inhibitor of the anti-apoptotic proteins Bcl-2, Bcl-X(L) and Bcl-w, with an affinity two to three orders of magnitude more potent than previously reported compounds. Mechanistic studies reveal that ABT-737 does not directly initiate the apoptotic process, but enhances the effects of death signals, displaying synergistic cytotoxicity with chemotherapeutics and radiation. ABT-737 exhibits single-agent-mechanism-based killing of cells from lymphoma and small-cell lung carcinoma lines, as well as primary patient-derived cells, and in animal models, ABT-737 improves survival, causes regression of established tumours, and produces cures in a high percentage of the mice.     

Machaeridians are Palaeozoic armoured annelids

The systematic affinities of several Palaeozoic skeletal taxa were only resolved when their soft-tissue morphology was revealed by the discovery of exceptionally preserved specimens. The conodonts provide a classic example, their tooth-like elements having been assigned to various invertebrate and vertebrate groups for more than 125 years until the discovery of their soft tissues revealed them to be crown-group vertebrates. Machaeridians, which are virtually ubiquitous as shell plates in benthic marine shelly assemblages ranging from Early Ordovician (Late Tremadoc) to Carboniferous, have proved no less enigmatic. The Machaeridia comprise three distinct families of worm-like animals, united by the possession of a dorsal skeleton of calcite plates that is rarely found articulated. Since they were first described 150 years ago machaeridians have been allied with barnacles, echinoderms, molluscs or annelids. Here we describe a new machaeridian with preserved soft parts, including parapodia and chaetae, from the Upper Tremadoc of Morocco, demonstrating the annelid affinity of the group. This discovery shows that a lineage of annelids evolved a dorsal skeleton of calcareous plates early in their history; it also resolves the affinities of a group of problematic Palaeozoic invertebrates previously known only from isolated elements and occasional skeletal assemblages.     

A molecular solution to the riddle of the giant panda's phylogeny

Although it is generally agreed that the giant panda (Ailuropoda melanoleuca) is a member of the order Carnivora, there has long been disagreement over whether it should be classified with bears, raccoons or as a single member of its own family. Four independent molecular and genetic measures lead to a consensus phylogeny for the giant and lesser pandas. The lesser panda diverged from New World procyonids at approximately the same time as their departure from ursids, while ancestors of the giant panda split from the ursid lineage much later, just before the radiation which led to modern bears. The giant panda's divergence was accompanied by a chromosomal reorganization which can be partially reconstructed from the ursid karyotype, but not from that of procyonids or the lesser panda. The apparently dramatic, but actually limited, distinctions between the giant panda and the bears in chromosomal and anatomical morphology provide a graphic mammalian example of the discordance of molecular and morphological (and chromosomal) evolutionary change.     

Accessory cell-dependent selection of specific T-cell functions

Activation of many T-cell functions depends on their interaction with antigen-presenting accessory cells which express I region associated (Ia) products. Cells expressing accessory cell function include those of the monocyte/macrophage lineage and dendritic cells. More recently, B cells and a number of tumour cell lines of macrophage or B-cell origin were shown to act as accessory cells in certain assays. We showed previously that normal peritoneal exudate macrophages (PEC) induced both T-cell proliferation as well as T-cell help, whereas various Ia+ tumour lines of macrophage or B-cell origin, although stimulating antigen-specific T-cell proliferation, did not significantly activate T-cell help. We report here that during the initial T-cell activation in vitro accessory cells (PEC or Ia+ tumour cells) select particular T cells to express previously determined functions. Moreover, some tumour cell lines induce suppressor T cells which inhibit helper activity.     

Discovery of a pterodactylid pterosaur from the Yixian Formation of western Liaoning, China

A well-preserved pterosaur with nearly complete skull is described from the Lower Cretaceous Yixian Formation at Sihetun in western Liaoning. It is characterized by a low and long crestless skull, slender and pointed teeth, long metacarpal, nearly equal length of metatarsals I–III and short pedal digit V. It is referred to a new genus and species of the family Pterodactylidae:Haopterus gracilis gen. et sp. nov. This is the first pterosaur with a nearly complete skull from the Jehol Biota; it also represents the first non-controversial fossil record of Pterodactylidae in Asia.Haopterus is more derived thanPterodactylus from the Late Jurassic Solnhofen in Germany. This discovery extends the distribution of the family Pterodactylidae from Europe and Africa to Asia and its latest occurrence from the Late Jurassic to the Early Cretaceous. The discovery ofHaopterus gracilis provides further evidence for the study of the origin and radiation of the Jehol Biota; it also sheds new light on the evolution and distribution of pterosaurs in the late Mesozoic.     

A primitive sarcopterygian fish with an eyestalk

The discovery of two Early Devonian osteichthyan (bony fish) fossils has challenged established ideas about the origin of osteichthyans and their divergence into actinopterygians (teleosts and their relatives) and sarcopterygians (tetrapods, coelacanths, lungfishes and related groups). Psarolepis from China and an unnamed braincase from Australia combine derived sarcopterygian and actinopterygian characters with primitive features previously restricted to non-osteichthyans, suggesting that early osteichthyan evolution may have involved substantial parallellism between sarcopterygians and actinopterygians. But interpretation of these fossils has been hampered by poor phylogenetic resolution. Here we describe a basal sarcopterygian fish, Achoania gen, et sp. nov., that fills the morphological gap between Psarolepis and higher sarcoptergyians. We also report the presence of eyestalk attachments in both Achoania and Psarolepis, showing that this supposedly non-osteichthyan feature occurs in basal sarcopterygians as well as the actinoptergyian-like Australian braincase.     

Baryonyx, a remarkable new theropod dinosaur

An extremely large claw bone, some 30 cm long, was found in Wealden (Lower Cretaceous) deposits in a Surrey claypit in January 1983. This led to the discovery the following month of the well-preserved skeleton of a new large theropod dinosaur. Only one other theropod specimen comprising more than a few bones had ever been found in Britain, and that discovery was more than a century ago. Indeed, no large theropod, reasonably complete, had previously been discovered in Lower Cretaceous rocks anywhere in the world. Our study so far suggests that the Surrey dinosaur was a typical large theropod in certain respects, resembling, for example Allosaurus. In several other respects, however, it differs sufficiently from all known dinosaurs to merit designation as the representative of a new species, genus and family.     

Genome duplication in the teleost fish Tetraodon nigroviridis reveals the early vertebrate proto-karyotype

Tetraodon nigroviridis is a freshwater puffer fish with the smallest known vertebrate genome. Here, we report a draft genome sequence with long-range linkage and substantial anchoring to the 21 Tetraodon chromosomes. Genome analysis provides a greatly improved fish gene catalogue, including identifying key genes previously thought to be absent in fish. Comparison with other vertebrates and a urochordate indicates that fish proteins have diverged markedly faster than their mammalian homologues. Comparison with the human genome suggests approximately 900 previously unannotated human genes. Analysis of the Tetraodon and human genomes shows that whole-genome duplication occurred in the teleost fish lineage, subsequent to its divergence from mammals. The analysis also makes it possible to infer the basic structure of the ancestral bony vertebrate genome, which was composed of 12 chromosomes, and to reconstruct much of the evolutionary history of ancient and recent chromosome rearrangements leading to the modern human karyotype.     

西藏林芝地区林芝村古墓葬调查简报

文章对新发现的西藏林芝地区林芝村古墓葬的考古材料作了简单介绍,文中通过对该墓地出土的陶器及其相关问题的分析,认为墓地的年代可能为吐蕃部落时期或前吐蕃王朝时期。该墓地发现的遗物纠正了过去林芝地区早期文化的陶器中“仅见平底器”的看法,为重新认识并进一步探讨“林芝文化类型”提供了重要而新颖的实证材料。同时,从一个侧面反映出林芝地区早期文化的多样性和丰富性。     

Evidence for several waves of global transmission in the seventh cholera pandemic

Vibrio cholerae is a globally important pathogen that is endemic in many areas of the world and causes 3-5 million reported cases of cholera every year. Historically, there have been seven acknowledged cholera pandemics; recent outbreaks in Zimbabwe and Haiti are included in the seventh and ongoing pandemic. Only isolates in serogroup O1 (consisting of two biotypes known as 'classical' and 'El Tor') and the derivative O139 can cause epidemic cholera. It is believed that the first six cholera pandemics were caused by the classical biotype, but El Tor has subsequently spread globally and replaced the classical biotype in the current pandemic. Detailed molecular epidemiological mapping of cholera has been compromised by a reliance on sub-genomic regions such as mobile elements to infer relationships, making El Tor isolates associated with the seventh pandemic seem superficially diverse. To understand the underlying phylogeny of the lineage responsible for the current pandemic, we identified high-resolution markers (single nucleotide polymorphisms; SNPs) in 154 whole-genome sequences of globally and temporally representative V. cholerae isolates. Using this phylogeny, we show here that the seventh pandemic has spread from the Bay of Bengal in at least three independent but overlapping waves with a common ancestor in the 1950s, and identify several transcontinental transmission events. Additionally, we show how the acquisition of the SXT family of antibiotic resistance elements has shaped pandemic spread, and show that this family was first acquired at least ten years before its discovery in V. cholerae.