Origins of polyploids: an example from peonies (Paeonia) and a model for angiosperms

The majority of tetraploid peonies are allopolyploids derived from crosses between phylogenetically distinct diploid lineages. Tetraploid Paeonia obovata was previously considered to be an autopolyploid because it is morphologically indistinguishable from the diploid of the same species. The presence of the Adh2 gene in tetraploid P. obovata but the inability to amplify the Adh2 gene from Chinese diploids of P. obovata, however, suggests that the tetraploid was not an autotetraploid derivative of the geographically adjacent diploid populations in China. The Adh gene phylogenies rather suggest that the tetraploid originated from crosses between two geographical races of diploid P. obovata distributed in China and Japan. The intermediate status of tetraploid P. obovata between auto‐ and allopolyploidy highlights the need for population genetic analyses of polyploid origins along the continuous range of genomic divergence. Here we present a model that describes the probabilities of polyploid formation and establishment as a function of genomic divergence between diploid progenitors. The probability of polyploid formation (P_f) is obtained from the multiplication of the probability of production of unreduced gametes (P_g) and the probability of ‘hybridization’ (P_h). P_f stays relatively stable when the genomic divergence is low, and then decreases progressively rapidly with the increase of genomic divergence between diploid progenitors. The probability of polyploid establishment (P_e), which depends on the rate of appearance of stable beneficial gene combinations and the rate of fertility restoration, is positively correlated with the genomic divergence of diploid parents. Multiplication of P_f and P_e gives an overall probability of polyploid origins (P_o) that varies continuously along the genomic divergence between diploid progenitors. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82 , 561–571.     

Efficient, chemoselective synthesis of immunomicelles using single-domain antibodies with a C-terminal thioester

Background  

Classical bioconjugation strategies for generating antibody-functionalized nanoparticles are non-specific and typically result in heterogeneous compounds that can be compromised in activity. Expression systems based on self-cleavable intein domains allow the generation of recombinant proteins with a C-terminal thioester, providing a unique handle for site-specific conjugation using native chemical ligation (NCL). However, current methods to generate antibody fragments with C-terminal thioesters require cumbersome refolding procedures, effectively preventing application of NCL for antibody-mediated targeting and molecular imaging.     

Late Pliocene vegetation and climate of Zhangcun region,Shanxi, North China

To understand the Neogene climatic changes in eastern Asia and evaluate the intercontinental climatic differences, we have quantitatively reconstructed the vegetation successions and climatic changes in the late Pliocene Zhangcun area based on the palynological data and explored the regional climatic differences between central Europe and eastern Asia. The late Pliocene palynological assemblage of Zhangcun, Shanxi was composed of 63 palynomorphs, belonging to 50 families, covering angiosperms (90.2%), gymnosperms (9.7%), ferns (0.09%), and other elements (0.02%). Four periods of vegetation succession over time were recognized. In period 1, a needle‐ and broad‐leaved mixed forest prevailed with a cool and dry climate. Period 2 was characterized by an expansion of forest with a warmer and wetter climate. The number of conifers increased and that of herbs decreased in period 3, and the climate became cool and dry. In period 4, the forest was dominated by conifers and reflecting a cooler climate. The data of seven climatic parameters in general and four periods estimated by the Coexistence Approach suggested that (1) The late Pliocene temperatures and precipitations were higher than today. (2) The Neogene climate of both Central Europe and North China exhibited a general cooling and drying trend although the mean annual temperature dropped by ca. 1 °C in North China, vs. ca. 7 °C in Central Europe from the middle Miocene to the late Pliocene. (3) The decline of the mean maximum monthly precipitation might signal a weakening of the summer monsoon. (4) The decline of both the mean coldest monthly temperature and the mean minimum monthly precipitation might be linked to the strengthening of the winter monsoon in eastern Asia. (5) The rapid uplift of the Tibetan Plateau strengthened the climatic cooling and drying during the late Pliocene of the Zhangcun region.     

Seeing Like an Oil Company: Space, Security, and Global Capital in Neoliberal Africa

In this article, I seek to identify a limitation in the analysis James Scott offers in Seeing Like a State (1998) by asking to what extent his account of the follies of schemes for planned improvement by states provides critical leverage on the present world of neoliberal global capitalism. Scott has claimed that a dynamic of standardization, homogenization, and grid making applies not only to developmentalist states but also equally to the contemporary world of downsized states and unconstrained global corporations. I contest that claim by tracing how recent capital investment in Africa has been territorialized, and some of the new forms of order and disorder that have accompanied that selectively territorialized investment. Because such investment has been overwhelmingly in mineral resource extraction—particularly in oil—a contrast will become visible between the homogenizing, standardizing state optic Scott analyzed and a rather different way of seeing, proper to the contemporary global oil company.     

Empirical evaluation of preservation methods for faecal DNA

We evaluate the relative effectiveness of four methods for preserving faecal samples for DNA analysis. PCR assays of fresh faecal samples collected from free-ranging baboons showed that amplification success was dependent on preservation method, PCR-product size, and whether nuclear or mitochondrial DNA was assayed. Storage in a DMSO/EDTA/Tris/salt solution (DETs) was most effective for preserving nuclear DNA, but storage in 70% ethanol, freezing at –20°C and drying performed approximately equally well for mitochondrial DNA and short (<200 bp) nuclear DNA fragments. Because faecal DNA is diluted and degraded, repeated extractions from faeces may be necessary and short nuclear markers should be employed for genotyping. A review of molecular scatology studies further suggests that three to six faeces per individual should be collected.     

Evaluation of the various components of the Nasonov pheromone used by clustering honeybees

ABSTRACT. Of the various components of the Nasonov pheromone, geraniol, (E)-citral and nerolic acid were the most important for inducing clustering. The presence of (Z)-citral with (E)-citral, or in a mixture of components including (E)-citral, did not diminish clustering and sometimes increased it. Geranic acid alone encouraged clustering, but was less effective with nerolic acid or the citrals. Nerol and (E, E)-farnesol had little obvious influence on clustering. A 1:1:1 mixture of geraniol + nerolic acid + (E)- and (Z)-citrals was as effective as a mixture of all the seven components in equal proportions, which was in turn as effective as a mixture containing the components in the proportions present naturally in the Nasonov gland.     

Membrane Lipids in Senescing Green Tissues2

At a late stage in sensescence cucumber cotuledons lose freshweight rapidly; at the same time there is an increase in apparentfree space and large quantities of electrolyte leak out whendiscs of cotyledon tissue are floated on water. It is concludedthat tonoplast and plasma membrane become leaky at this time. Phosphatidyl choline, the major phospholipid present, beginsto disappear once the cotyledons reach maximum fresh weight;by the time rapid water loss starts, 56 per cent has gone, andphosphatidyl ethanolamine and inositol start to disappear. Onlyat maturity is there enough of these phospholipids to furnishmore than two complete membranes around each cell; it is suggestedthat the decline in phospholipid level at senescence destroysmembrane integrity and allows leakage. The glyohpids begin to disappear at the same time as chlorophyll,2 weeks before weight loss starts. The minor lipid phosphatidyl glycerol is the first to disappearfrom the cotyledons.     

Tempo and mode of concerted evolution in the L1 repeat family of mice

A 300-bp DNA sequence has been determined for 30 (10 from each of three species of mice) random isolates of a subset of the long interspersed repeat family L1. From these data we conclude that members of the L1 family are evolving in concert at the DNA sequence level in Mus domesticus, Mus caroli, and Mus platythrix. The mechanism responsible for this phenomenon may be either duplicative transposition, gene conversion, or a combination of the two. The amount of intraspecies divergence averages 4.4%, although between species base substitutions accumulate at the rate of approximately 0.85%/Myr to a maximum divergence of 9.1% between M. platythrix and both M. domesticus and M. caroli. Parsimony analysis reveals that the M. platythrix L1 family has evolved into a distinct clade in the 10-12 Myr since M. platythrix last shared a common ancestor with M. domesticus and M. caroli. The parsimony tree also provides a means to derive the average half-life of L1 sequences in the genome. The rates of gain and loss of individual copies of L1 were estimated to be approximately equal, such that approximately one-half of them turn over every 3.3 Myr.