Sex ratios under asymmetrical local mate competition in the parasitoid wasp Nasonia vitripennis

Sex ratio theory has proved remarkably useful in testing theadaptive nature of animal behavior. A particularly productivearea in this respect is Hamilton's theory of local mate competition(LMC), which has been extended in numerous directions to includegreater biological realism, allowing more detailed tests inspecific organisms. We have presented one such extension, termedasymmetrical LMC, which occurs when egg laying by females ona patch is asynchronous, and emerging males do not disperse,resulting in the extent of LMC on a patch varying over time.Our aim here is to test whether the parasitoid wasp Nasoniavitripennis responds to variation in the degree of asymmetricalLMC. Specifically, we show that females adjust their offspringsex ratios in response to (1) variation in the amount of asynchronyin emergence between broods on a patch and (2) the number andproportion of previously parasitized hosts on the patch. Ourresults provide qualitative support for the predictions of theory,suggesting new levels of complexity in the sex ratio behaviorof this much-studied organism. However, our results do not alwaysprovide quantitative support for theory, suggesting furthercomplexities that must be clarified.     

Collagen receptors mediate early events in the attachment of epithelial (MDCK) cells

Summary Madin-Darby canine kidney (MDCK) cells kept in suspension culture for 12–15 hr displayed high-affinity binding sites for¹²⁵I-lathyritic (soluble) collagen (120,000/cell,K _D =30nm) and preferred collagens types I and IV over laminin or fibronectin as substrates during the first hour of attachment. On the other hand, after 4 hr, attachment to all four substrates was equally efficient. Upon challenge with a collagen substrate, the high-affinity sites were rapidly recruited on it (T1/2=6 min). Their occupancy by soluble collagen triggered the exocytosis of a second large population of low-affinity collagen binding sites that included laminin and seems to be involved in a second cell-attachment mechanism. These results are compatible with a twostep model of MDCK cell attachment to the substrate: first, via high-affinity collagen binding sites, and second, via laminin of cellular origin.     

Hydrolysis of fish oil by hyperactivated rhizomucor miehei lipase immobilized by multipoint anion exchange

Rhizomucor miehei lipase (RML) is greatly hyperactivated (around 20‐ to 25‐fold toward small substrates) in the presence of sucrose laurate. Hyperactivation appears to be an intramolecular process because it is very similar for soluble enzymes and covalently immobilized derivatives. The hyperactivated enzyme was immobilized (in the presence of sucrose laurate) on cyanogen bromide‐activated Sepharose (very mild covalent immobilization through the amino terminal residue), on glyoxyl Sepharose (intense multipoint covalent immobilization through the region with the highest amount of Lys residues), and on different anion exchangers (by multipoint anionic exchange through the region with the highest density of negative charges). Covalent immobilization does not promote the fixation of the hyperactivated enzyme, but immobilization on Sepharose Q retains the hyperactivated enzyme even in the absence of a detergent. The hydrolysis of fish oils by these hyperactivated enzyme derivatives was sevenfold faster than by covalently immobilized derivatives and three and a half times faster than by the enzyme hyperactivated on octyl‐Sepharose. The open structure of the hyperactivated lipase is fairly exposed to the medium, and no steric hindrance should interfere with the hydrolysis of large substrates. These new hyperactivated derivatives seem to be more suitable for hydrolysis of oils by RML immobilized inside porous supports. In addition, the hyperactivated derivatives are fairly stable against heat and organic cosolvents. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011     

Understanding plant reproductive diversity

Flowering plants display spectacular floral diversity and a bewildering array of reproductive adaptations that promote mating, particularly outbreeding. A striking feature of this diversity is that related species often differ in pollination and mating systems, and intraspecific variation in sexual traits is not unusual, especially among herbaceous plants. This variation provides opportunities for evolutionary biologists to link micro-evolutionary processes to the macro-evolutionary patterns that are evident within lineages. Here, I provide some personal reflections on recent progress in our understanding of the ecology and evolution of plant reproductive diversity. I begin with a brief historical sketch of the major developments in this field and then focus on three of the most significant evolutionary transitions in the reproductive biology of flowering plants: the pathway from outcrossing to predominant self-fertilization, the origin of separate sexes (females and males) from hermaphroditism and the shift from animal pollination to wind pollination. For each evolutionary transition, I consider what we have discovered and some of the problems that still remain unsolved. I conclude by discussing how new approaches might influence future research in plant reproductive biology.     

The Mechanism of Supercoiled DNA Recognition by Eukaryotic Type I Topoisomerases: II. A Comparison of the Enzyme Interaction with Specific and Nonspecific Oligonucleotides

Data on the interaction of DNA type I topoisomerases from the murine and human placenta cells with specific and nonspecific oligonucleotides of various structures and lengths are summarized. The relative contributions of various contacts between the enzymes and DNA that have previously been detected by X-ray analysis to the total affinity of the topoisomerases for DNA substrates are estimated. Factors that determine the differences in the enzyme interactions with specific and nonspecific single- and double-stranded DNAs are revealed. The results of the X-ray analysis of human DNA topoisomerase I are interpreted taking into account data on the comprehensive thermodynamic and kinetic analysis of the enzyme interaction with the specific and nonspecific DNAs.     

Multiomic Metabolic Enrichment Network Analysis Reveals Metabolite–Protein Physical Interaction Subnetworks Altered in Cancer

Metabolism is recognized as an important driver of cancer progression and other complex diseases, but global metabolite profiling remains a challenge. Protein expression profiling is often a poor proxy since existing pathway enrichment models provide an incomplete mapping between the proteome and metabolism. To overcome these gaps, we introduce multiomic metabolic enrichment network analysis (MOMENTA), an integrative multiomic data analysis framework for more accurately deducing metabolic pathway changes from proteomics data alone in a gene set analysis context by leveraging protein interaction networks to extend annotated metabolic models. We apply MOMENTA to proteomic data from diverse cancer cell lines and human tumors to demonstrate its utility at revealing variation in metabolic pathway activity across cancer types, which we verify using independent metabolomics measurements. The novel metabolic networks we uncover in breast cancer and other tumors are linked to clinical outcomes, underscoring the pathophysiological relevance of the findings.     

The impact of tick parasites on the behaviour of the lizard Tiliqua rugosa

Populations of the Australian sleepy lizard, Tiliqua rugosa, near Mt. Mary, South Australia carry natural infestations of two tick species Aponomma hydrosauri and Amblyomma limbatum. In field experiments at two sites, 18 km apart, lizards with experimentally increased tick loads had smaller home ranges, moved shorter distances in a day, and were found basking more but moving less often than lizards from which ticks were experimentally removed. The results were consistent for adult lizards in two years, and for sub-adults in a third year. Laboratory trials showed that juvenile lizards that had tick infestations had lower sprint speeds than uninfested siblings, and that adults with tick infestations had less endurance than those that were uninfested. The results contrast with those of a previous survey that showed that lizards with high tick loads had greater body size and remained longer at a site, but indicate that there may be a balance, for lizards, between the fitness advantages in occupying habitats with high-quality resources, and the costs from parasites that also prefer those habitats. Received: 02 March 1999 / Accepted: 07 October 1999     

Somatostatin-detergent interaction

The effect of cationic, anionic and nonionic detergents on the EPR spectrum of spin-labeled somatostatin has been studied. At detergent concentrations well above the critical micelle concentration, nonionic detergents do not alter the EPR spectrum. Sodium dodecyl sulfate markedly alters both the line height ratio and the hyperfine splitting constant, whilst dodecyltrimethylammonium bromide alters only slightly the hyperfine splitting constant and line height ratio. The somatostatin-sodium dodecyl sulfate complex appeared monodisperse by sedimentation equilibrium with about 17 g bound detergent per g peptide. Circular dichroic and difference spectra of the dodecyl sulfate-somatostatin complex show that the tryptophanyl residue is buried in a nonpolar environment and that the secondary and tertiary structure of the peptide is markedly altered. Sedimentation equilibrium studies suggest that two types of dodecyltrimethylammonium-somatostatin complex exist. One type resembles the dodecyl sulfate-peptide complex, whilst the other appears to include several peptide units with only about one gram bound detergent per gram peptide.     

Male-biased sex ratios in mature damselfly populations: real or artefact?

1. There is ongoing controversy about whether biased sex ratios in diploid insect populations are real or an artefact caused by different behaviours and/or different catchability of the sexes. This was tested by monitoring two field and three semi-natural populations of the damselfly Lestes sponsa. 2. Capture–mark–recapture data showed that population size estimates were about twice as large for males as for females at both field sites. Independent estimates of the sex ratios based on total numbers of males and females captured supported the male bias. 3. Males had higher recapture probabilities than females due to longer times between successive visits in females. Because the same pattern was found in the semi-natural populations, the longer intervals in females are no artefact due to their lower detectability. 4. Theoretical models show that the strong temporary emigration of females tends, if anything, to overestimate female population sizes and that the heterogeneity of recapture probabilities observed in males tends to underestimate male population sizes. Hence, behavioural differences between the sexes do not cause an artificially male-biased sex ratio. 5. Spatial data show that operational sex ratios are male biased at the pond but become female biased in the plots further away from the shoreline; however because of the decrease in densities away from the shoreline, this does not result in a global even sex ratio. 6. Spatial data, temporary emigration patterns, and independent estimates suggest strongly that the male-biased sex ratios in mature damselfly populations are real.     

Structural Insight into Chromatin Recognition by Multiple Domains of the Tumor Suppressor RBBP1

Retinoblastoma-binding protein 1 (RBBP1) is involved in gene regulation, epigenetic regulation, and disease processes. RBBP1 contains five domains with DNA-binding or histone-binding activities, but how RBBP1 specifically recognizes chromatin is still unknown. An AT-rich interaction domain (ARID) in RBBP1 was proposed to be the key region for DNA-binding and gene suppression. Here, we first determined the solution structure of a tandem PWWP-ARID domain mutant of RBBP1 after deletion of a long flexible acidic loop L12 in the ARID domain. NMR titration results indicated that the ARID domain interacts with DNA with no GC- or AT-rich preference. Surprisingly, we found that the loop L12 binds to the DNA-binding region of the ARID domain as a DNA mimic and inhibits DNA binding. The loop L12 can also bind weakly to the Tudor and chromobarrel domains of RBBP1, but binds more strongly to the DNA-binding region of the histone H2A-H2B heterodimer. Furthermore, both the loop L12 and DNA can enhance the binding of the chromobarrel domain to H3K4me3 and H4K20me3. Based on these results, we propose a model of chromatin recognition by RBBP1, which highlights the unexpected multiple key roles of the disordered acidic loop L12 in the specific binding of RBBP1 to chromatin.