Zhailimeryx, A New Lophiomerycid Artiodactyl (Mammalia) from the Late Middle Eocene of Central China and the Early Evolution of Ruminants

A new genus and species of primitive selenodont artiodactyl, Zhailimeryx jingweni, occurs in the late middle Eocene Zhaili Member of the Heti Formation, Yuanqu Basin, Shanxi Province, China. A phylogenetic analysis of dental characters suggests that Zhailimeryx is closely related to Lophiomeryx and other lophiomerycid ruminants of Asia and Europe. Zhailimeryx and other Eocene records of Lophiomerycidae from Asia support an Asian origin for this family, followed by dispersal into Europe both before and after the Grande Coupure. Morphological evidence from Zhailimeryx suggests that ruminant artiodactyls had already undergone substantial diversification prior to the late middle Eocene, and it reopens the issue of whether the higher taxa Tragulina and Pecora are valid expressions of ruminant phylogeny.     

Mutations in the WRN gene in mice accelerate mortality in a p53-null background

Werner's syndrome (WS) is a human disease with manifestations resembling premature aging. The gene defective in WS, WRN, encodes a DNA helicase. Here, we describe the generation of mice bearing a mutation that eliminates expression of the C terminus of the helicase domain of the WRN protein. Mutant mice are born at the expected Mendelian frequency and do not show any overt histological signs of accelerated senescence. These mice are capable of living beyond 2 years of age. Cells from these animals do not show elevated susceptibility to the genotoxins camptothecin or 4-NQO. However, mutant fibroblasts senesce approximately one passage earlier than controls. Importantly, WRN(-/-);p53(-/-) mice show an increased mortality rate relative to WRN(+/-);p53(-/-) animals. We consider possible models for the synergy between p53 and WRN mutations for the determination of life span.     

Influence of phosphate on activity and stability of reverse transcriptase from avian myeloblastosis virus.

Activity of RNA-dependent DNA polymerase (RDDP) from avian myeloblastosis virus (AMV), either in purified form or in virus lysates, was increased by phosphorylation. Stability of RDDP in lysates buffered with phosphate was much greater (no loss of activity in 48 hours at 4 degrees) than that in lysates buffered with Tris-Cl (76% loss). Activity lost in the Tris-buffered extracts was completely restored by phosphorylation. The findings suggested that AMV RDDP activity is influenced by the degree of phosphorylation of the enzyme or enzyme-associated proteins and that this chemical modification is mediated by protein phosphokinase and phosphoprotein phosphatase present in crude extracts of purified AMV. Application of these results provided the basis of procedures whereby RDDP can be recovered in significantly higher yield and purity than formerly.     

Role of the cell surface in bacterial mating: requirement for intact mucopeptide in donors for the expression of surface exclusion in R+ strains of Escherichia coli.

Two derivatives of the F-like R factor R1drd19 carrying mutually exclusive resistance determinants were used to study the role of the mucopeptide in the expression of conjugal functions. The use of metabolically active penicillin spheroplasts in R+ times R- matings had no effect on the ability of the cells to donate or accept a plasmid. However, in R+ times R+ matings it was found that surface exclusion was totally abolished if the donor, but not the recipient, was a spheroplast. This result implies that the traS gene, expressed by the excluding plasmid, is dependent for its action on an intact mucopeptide layer in the donor cell, and that this interaction is independent of the transfer ability of the excluding plasmid.     

Zygospores of selected Trichomycetes in larval Diptera of the families Chironomidae and Simuliidae

The midgut-inhabiting fungi (Harpellaceae) Harpella melusinae and Stachylina pedifer were induced to form zygospores, using an application of a pH 10 potassium hydroxide solution with culture media. The previously unknown zygospores of S. pedifer are borne perpendicular to the zygosporophore, as in Harpella melusinae. The zygospores of the hindgut-inhabiting species Smittium coloradense, borne obliquely to the zygosporophore (in vivo), are described for the first time.     

Productive replication of adeno-associated virus can occur in human papillomavirus type 16 (HPV-16) episome-containing keratinocytes and is augmented by the HPV-16 E2 protein

We used a sensitive assay to test whether an adeno-associated virus (AAV) productive replication cycle can occur in immortalized human keratinocytes carrying episomal human papillomavirus type 16 (HPV-16) DNA. Following transfection with cloned AAV DNA, infectious AAV was produced, and the infectivity was blocked by anti-AAV antiserum. The HPV-16 E2 protein substantially increased the yield of AAV. Other HPV early proteins did not, in our experiments, show this ability. E2 has been shown to be able to affect p53 levels and to block cell cycle progression at mitosis. We tested the effect of changes in p53 expression on AAV replication and found that large differences in the level of p53 did not alter AAV DNA replication. In extension of this, we found that cellular help for AAV in response to stress was also independent of p53. To test if a mitotic block could trigger AAV DNA replication, we treated the cells with the mitotic inhibitor nocodazole. AAV DNA replication was stimulated by the presence of nocodazole in these and a number of other cell types tested. Yields of infectious virus, however, were not increased by this treatment. We conclude that the HPV-16 E2 protein stimulates AAV multiplication in these cells and propose that this occurs independently of the effects of E2 on p53 and cell cycle progression. Since the effect of E2 was not seen in keratinocytes lacking the HPV-16 episome, we suggest that E2 can help AAV by working in concert with other HPV-16 proteins.     

Quantifying Ecosystem Controlsand Their Contextual Interactionson Nutrient Export fromDeveloping Forest Mesocosms

The complexity of natural ecosystems makes it difficult to compare the relative importance of abiotic and biotic factors and to assess the effects of their interactions on ecosystem development. To improve our understanding of ecosystem complexity, we initiated an experiment designed to quantify the main effects and interactions of several factors that are thought to affect nutrient export from developing forest ecosystems. Using a replicated 2 × 2 × 4 factorial experiment, we quantified the main effects of these factors and the factor interactions on annual calcium, magnesium, and potassium export from field mesocosms over 4 years for two Vermont locations, two soils, and four different tree seedling communities. We found that the main effects explained 56%–97% of total variation in nutrient export. Abiotic factors (location and soil) accounted for a greater percentage of the total variation in nutrient export (47%–94%) than the biotic factor (plant community) (2%–15%). However, biotic control over nutrient export was significant, even when biomass was minimal. Factor interactions were often significant, but they explained less of the variation in nutrient export (1%–33%) than the main effects. Year-to-year fluctuations influenced the relative importance of the main effects in determining nutrient export and created factor interactions between most of the explanatory variables. Our study suggests that when research is focused on typically used main effects, such as location and soil, and interactions are aggregated into overall error terms, important information about the factors controlling ecosystem processes can be lost.     

Identification of molecular markers in soybean comparing RFLP,RAPD and AFLP DNA mapping techniques

Three different DNA mapping techniques—RFLP, RAPD and AFLP—were used on identical soybean germplasm to compare their ability to identify markers in the development of a genetic linkage map. Polymorphisms present in fourteen different soybean cultivars were demonstrated using all three techniques. AFLP, a novel PCR-based technique, was able to identify multiple polymorphic bands in a denaturing gel using 60 of 64 primer pairs tested. AFLP relies on primers designed in part on sequences for endonuclease restriction sites and on three selective nucleotides. The 60 diagnostic primer pairs tested for AFLP analysis each distinguished on average six polymorphic bands. Using specific primers designed for soybean fromEco RI andMse I restriction site sequences and three selective nucleotides, as many as 12 polymorphic bands per primer could be obtained with AFLP techniques. Only 35% of the RAPD reactions identified a polymorphic band using the same soybean cultivars, and in those positive reactions, typically only one or two polymorphic bands per gel were found. Identification of polymorphic bands using RFLP techniques was the most cumbersome, because Southern blotting and probe hybridization were required. Over 50% of the soybean RFLP probes examined failed to distinguish even a single polymorphic band, and the RFLP probes that did distinguish polymorphic bands seldom identified more than one polymorphic band. We conclude that, among the three techniques tested, AFLP is the most useful.     

Golgin-84 is a rab1 binding partner involved in Golgi structure

Members of the golgin family of coiled-coil proteins have been implicated in the tethering of vesicles to Golgi membranes and cisternal membranes to each other. Many also bind to rab GTPases. Golgin-84 is a membrane-anchored golgin that we now show binds preferentially to the GTP form of the rab1 GTPase. It is also present throughout the Golgi stack by immuno-EM. Antibodies to golgin-84 inhibit stacking of cisternal membranes in a cell-free assay for Golgi reassembly, whereas the cytoplasmic domain of golgin-84 stimulates stacking and increases the length of re-assembled stacks. Transient expression of golgin-84 in NRK cells helps prevent the disassembly of the Golgi apparatus normally triggered by treatment with brefeldin A. Together these data suggest that golgin-84 is involved in generating and maintaining the architecture of the Golgi apparatus.