Pretender punishment induced by chemical signalling in a queenless ant

Animal societies are stages for both conflict and cooperation. Reproduction is often monopolized by one or a few individuals who behave aggressively to prevent subordinates from reproducing (for example, naked mole-rats, wasps and ants). Here we report an unusual mechanism by which the dominant individual maintains reproductive control. In the queenless ant Dinoponera quadriceps, only the alpha female reproduces. If the alpha is challenged by another female she chemically marks the pretender who is then punished by low-ranking females. This cooperation between alpha and low-rankers allows the alpha to inflict punishment indirectly, thereby maintaining her reproductive primacy without having to fight.     

N-Acetoxy-acetylaminofluorene reacts preferentially with a control region of intracellular SV40 chromosome

Many chemical carcinogens or their metabolites react with DNA; thus it is of interest to determine what effect chromosomal structure has on these reactions. The chromosome of simian virus 40 (SV40) is well suited for such studies; like chromatin of eukaryotic cells, it is organized into nucleosomes. The nucleotide sequence of SV40 is known, together with much about the pattern of viral gene expression and DNA replication, and the structure of the viral chromosome. We have investigated the binding of the ultimate carcinogen, N-acetoxy-acetylaminofluorene (AAAF), to specific regions of the SV40 chromosome in situ in the intact infected cell. The results, reported here, indicate that a region containing regulatory functions on the intracellular SV40 chromosome has unique structural properties which render it more susceptible to attack by AAAF than the rest of the SV40 genome. The preferential binding of AAAF to regulatory regions of chromatin may have implications for the mechanism of action of this and similar carcinogens.     

Development and maintenance of B and T lymphocytes requires antiapoptotic MCL-1

Regulated apoptosis is essential for both the development and the subsequent maintenance of the immune system. Interleukins, including IL-2, IL-4, IL-7 and IL-15, heavily influence lymphocyte survival during the vulnerable stages of VDJ rearrangement and later in ensuring cellular homeostasis, but the genes specifically responsible for the development and maintenance of lymphocytes have not been identified. The antiapoptotic protein MCL-1 is an attractive candidate, as it is highly regulated, appears to enhance short-term survival and functions at an apical step in genotoxic deaths. However, Mcl-1 deficiency results in peri-implantation lethality. Here we show that mice conditional for Mcl-1 display a profound reduction in B and T lymphocytes when MCL-1 is removed. Deletion of Mcl-1 during early lymphocyte differentiation increased apoptosis and arrested the development at pro-B-cell and double-negative T-cell stages. Induced deletion of Mcl-1 in peripheral B- and T-cell populations resulted in their rapid loss. Moreover, IL-7 both induced and required MCL-1 to mediate lymphocyte survival. Thus, MCL-1, which selectively inhibits the proapoptotic protein BIM, is essential both early in lymphoid development and later on in the maintenance of mature lymphocytes.     

First skulls of the early Eocene primate Shoshonius cooperi and the anthropoid-tarsier dichotomy

The phylogenetic relationships of living tarsiers and extinct omomyid primates are critical for deciphering the origin and relationships of primate higher taxa, particularly anthropoids. Three competing phylogenetic hypotheses are: (1) tarsiers are most closely related to early Cenozoic Omomyidae, particularly genera such as Necrolemur from the late Eocene of Europe; (2) tarsiers share a more recent common ancestry with anthropoids than they do with any known omomyid; (3) tarsiers and/or omomyids are most closely related to strepsirhines. The anatomy of four skulls of the early Eocene omomyid Shoshonius cooperi--the first cranial material recovered for this genus--strongly suggests that Shoshonius shares a more recent common ancestry with Tarsius than do either anthropoids or other Eocene omomyids for which cranial anatomy is known. If the primate suborder Haplorhini (anthropoids, omomyids, tarsiids) is monophyletic, the phylogenetic position of Shoshonius requires that anthropoids and Tarsius diverged by at least the early Eocene, some 15 million years before the first appearance of anthropoids in the fossil record.     

The oldest known anthropoid postcranial fossils and the early evolution of higher primates

The middle Eocene primate family Eosimiidae, which is known from sites in central and eastern China and Myanmar, is central to efforts to reconstruct the origin and early evolution of anthropoid or 'higher' primates (monkeys, apes and humans). Previous knowledge of eosimiid anatomy has been restricted to the dentition and an isolated petrosal bone, and this limited anatomical information has led to conflicting interpretations of early anthropoid phylogeny. Here we describe foot bones of Eosimias from the same middle Eocene sites in China that yield abundant dental remains of this primate. Tarsals of Eosimias show derived anatomical traits that are otherwise restricted to living and fossil anthropoids. These new fossils substantiate the anthropoid status of Eosimias and clarify the phylogenetic position of anthropoids with respect to other major primate clades. Early anthropoids possessed a mosaic of primitive and derived traits in their postcranial skeletons, reflecting their derivation from haplorhine ancestors that retained many prosimian-like features.     

Esox lucius (Esocidae) and Stizostedion vitreum (Percidae) in the Green River basin, Colorado and Utah

Northern pike, Esox lucius , stocked in the Yampa River in 1977, invaded the mainstream Green River by 1981 and subsequently increased in range and abundance. The speed of this invasion is indicated by two recaptured pike that moved 78 and 110 km, respectively, downstream in about one year. Pike stomachs (n = 123) were usually empty (54.5%), but some contained fish (43%) and nonfish items (2.4%). Red shiner, Notropis lutrensis , and fathead minnow, Pimephales promelas , predominated among the 12 fish species eaten. Walleye, Stizostedion vitreum , presumably introduced to the Green River drainage in the 1960s, was widely distributed but low in abundance. Most of 61 adult walleye stomachs contained food (60.7%) ; of 6 fish species eaten, channel catfish, lctalurus punctatus , and fathead minnow were most frequently consumed. Northern pike and walleye were captured in habitats occupied by endangered Colorado River fishes, particularly Colorado squawfish, Ptychocheilus lucius . Predation on endangered fishes was not detected, but northern pike and walleye consumed at least three other native fishes. The northern pike may pose a threat to endangered fishes due to its population expansion, piscivory, and resource sharing. Diets of northern pike and walleye species should be further evaluated if their abundance increases.     

Nonnative Phragmites australis invasion into Utah wetlands

Phragmites australis (Cav.) Trin. ex Steud. (common reed), already one of the world’s most widespread plant species, has realized rapid range expansion in coastal wetlands of North America in the past century, but little is known about P. australis range expansion in inland wetland systems. We used genetic analyses, aerial photographs, field surveys, and a greenhouse experiment to study the extent and mechanism of nonnative P. australis invasion of Utah wetlands. We collected and genetically analyzed 39 herbarium samples across the state and 225 present-day samples from northern Utah’s major wetland complexes. All samples collected before 1993 and all samples collected outside the major wetlands of northern Utah, including some as recent as 2001, were identified as native (haplotypes A, B, D, and H). Only 10 (4%) of the present-day samples were native, each from small, discrete, low-density stands; the remaining samples were nonnative (haplotype M). Our earliest nonnative sample was collected near the Great Salt Lake in 1993. Around the Great Salt Lake, which contains 40% of Utah’s wetlands, P. australis cover has increased from 20% to 56% over the past 27 years—an increase that appears attributable to the nonnative strain. In a 3-month-long greenhouse experiment, the nonnative haplotype grew taller, had more aboveground biomass, and had a greater above- to belowground biomass ratio than the native haplotypes regardless of nitrogen, phosphorus, or water availability. Nonnative P. australis is rapidly invading the wetlands of northern Utah. Areas in Utah where the native P. australis remains should be identified and protected. Phragmites australis (Cav.) Trin ex Steud (carrizo), una de las especies de plantas más ampliamente distribuida en el mundo, se ha extendido rápidamente en los humedales costeros de Norteamérica en el último siglo, pero se conoce poco sobre la expansión de P. australis en sistemas de humedales del interior. Utilizamos análisis genéticos, fotografías aéreas, estudios de campo y un experimento en invernadero para examinar el alcance y el mecanismo de la invasión de la variedad no nativa de P. australis en los humedales de Utah. Recolectamos 39 muestras de herbario a lo largo del estado y 225 muestras actuales de los mayores complejos de humedales en el norte de Utah, y las sometimos a un análisis genético. Todas las muestras recolectadas antes de 1993 y las que se recolectaron fuera de los mayores humedales del norte de Utah, siendo las más recientes del 2001, fueron identificadas como nativas (haplotipos A, B, D y H). Solo 10 (4%) de las muestras actuales fueron nativas, todas de pequeños carrizales separados con baja densidad; las restantes fueron nonativas (haplotipo M). Nuestra muestra no nativa más antigua se recolectó cerca del Gran Lago Salado en 1993. Alrededor del Gran Lago Salado, el cual contiene el 40% de los humedales del estado de Utah, la cubierta de P. australis incrementó del 20% al 56% durante los últimos 27 años, un aumento que parece atribuirse a la variedad no nativa. En un experimento de invernadero de tres meses, el haplotipo no naivo creció más alto, tenía más biomasa sobre el nivel de la tierra y una mayor proporción de biomasa sobre el nivel de la tierra por biomasa subterránea que los haplotipos nativos sin importar la disponibilidad de nitrógeno, fósforo o agua. El haplotipo no nativo de P. australis está invadiendo rápidamente los humedales del norte de Utah. Las áreas en Utah en donde las variedades nativas permanecen deben ser identificadas y protegidas durante el manejo de carrizos.     

Virus-mediated killing of cells that lack p53 activity

A major goal of molecular oncology is to identify means to kill cells lacking p53 function. Most current cancer therapy is based on damaging cellular DNA by irradiation or chemicals. Recent reports support the notion that, in the event of DNA damage, the p53 tumour-suppressor protein is able to prevent cell death by sustaining an arrest of the cell cycle at the G2 phase. We report here that adeno-associated virus (AAV) selectively induces apoptosis in cells that lack active p53. Cells with intact p53 activity are not killed but undergo arrest in the G2 phase of the cell cycle. This arrest is characterized by an increase in p53 activity and p21 levels and by the targeted destruction of CDC25C. Neither cell killing nor arrest depends upon AAV-encoded proteins. Rather, AAV DNA, which is single-stranded with hairpin structures at both ends, elicits in cells a DNA damage response that, in the absence of active p53, leads to cell death. AAV inhibits tumour growth in mice. Thus viruses can be used to deliver DNA of unusual structure into cells to trigger a DNA damage response without damaging cellular DNA and to selectively eliminate those cells lacking p53 activity.