Coevolution between interspecific plant competitors?

The most important aspect of an individual's environment may be its individual neighbours; if so, microevolutionary selection pressure could be dominated by the competitors. Since biotic differentiation and coevolution of plant populations is a developing field in which there is strong interest, it has provoked keen discussion. Trifolium repens represents a particularly suitable example for an overview of the advances and criticism voiced in this research field.     

Epigenetic differences between sister chromatids?

Semi-conservative replication ensures that the DNA sequence of sister chromatids is identical except for replication errors and variation in the length of telomere repeats resulting from replicative losses and variable end processing. What happens with the various epigenetic marks during DNA replication is less clear. Many chromatin marks are likely to be copied onto both sister chromatids in conjunction with DNA replication, whereas others could be distributed randomly between sister chromatids. Epigenetic differences between sister chromatids could also emerge in a more predictable manner, for example, following processes that are associated with lagging strand DNA replication. The resulting epigenetic differences between sister chromatids could result in different gene expression patterns in daughter cells. This possibility has been difficult to test because techniques to distinguish between parental sister chromatids require analysis of single cells and are not obvious. Here, we briefly review the topic of sister chromatid epigenetics and discuss how the identification of sister chromatids in cells could change the way we think about asymmetric cell divisions and stochastic variation in gene expression between cells in general and paired daughter cells in particular.     

Do the evolutionary interactions between moths and bats promote niche partitioning between bats and birds?

Ecological theory suggests that the coexistence of species is promoted by the partitioning of available resources, as in dietary niche partitioning where predators partition prey. Yet, the mechanisms underlying dietary niche partitioning are not always clear. We used fecal DNA metabarcoding to investigate the diets of seven nocturnal insectivorous bird and bat species. Low diet overlap (2%–22%) supported resource partitioning among all species. Differences in diet corresponded with species identity, prey detection method, and foraging behavior of predators. Insects with ultrasonic hearing capabilities were consumed significantly more often by birds than bats, consistent with an evolved avoidance of echolocating strategies. In turn, bats consumed a greater proportion of noneared insects such as spruce budworms. Overall, our results suggest that evolutionary interactions among bats and moths translate to dietary niche partitioning and coexistence among bats and nocturnal birds.     

How do miniature pigs discriminate between people?. Discrimination between people wearing coveralls of the same colour

Seven experiments were conducted on four miniature pigs to determine: (1) whether the pigs can discriminate between people wearing the same coloured clothing; (2) what cues they rely on if they could discriminate. For 2 weeks before the experiments began, the pigs were conditioned in a Y-maze to receive raisins from the rewarder wearing dark blue coveralls. They were then given the opportunity to choose the rewarder or non-rewarder in these experiments. Each session consisted of 20 trials. Successful discrimination was that the pig chose the rewarder at least 15 times in 20 trials (P<0.05: by chi(2)-test). In Experiment 1, both rewarder and non-rewarder wore dark blue coveralls. By 20 sessions, all pigs successfully identified the rewarder. In Experiment 2: (1) both wore coveralls of the same new colours or (2) one of them wore coveralls of new colours. They significantly preferred the rewarder even though the rewarder and/or non-rewarder wore coveralls of new colours. In Experiment 3, both wore dark blue coveralls but olfactory cues were obscured and auditory cues were not given. The pigs were able to identify the rewarder successfully irrespective of changing auditory and olfactory cues. In Experiment 4, both wore dark blue coveralls but covered part of their face and body in different ways. The correct response rate decreased when a part of the face and the whole body of the rewarder and non-rewarder were covered. In Experiment 5, both wore dark blue coveralls and changed their apparent body size by shifting sitting position. The correct response rate increased as the difference in body size between the experimenters increased. In Experiment 6, the distance between the experimenters and the pig was increased by 30cm increments. The correct response rate of each pig decreased as the experimenters receded from the pig, but performance varied among the pigs. In Experiment 7, the light intensity of the experimental room was reduced from 550 to 80lx and then to 20lx. The correct response rate of each pig decreased with the reduction in light intensity, but all the pigs discriminated the rewarder from the non-rewarder significantly even at 20lx.In conclusion, the pigs were able to discriminate between people wearing coveralls of the same colour after sufficient reinforcement. These results indicate that pigs are capable of using visual cues to discriminate between people.     

Plant–pollinator interactions between an invasive and native plant vary between sites with different flowering phenology

Floral displays of invasive plants have positive and negative impacts on native plant pollination. Invasive plants may also decrease irradiance, which can lead to reduced pollination of native plants. The effects of shade and flowers of invasive plant species on native plant pollination will depend on overlap in flowering phenologies. We examined the effect of the invasive shrub Lonicera maackii on female reproductive success of the native herb Hydrophyllum macrophyllum at two sites: one with asynchronous flowering phenologies (slight overlap) and one with synchronous (complete overlap). At each site, we measured light availability, pollinator visitation, pollen deposition, and seed set of potted H. macrophyllum in the presence and absence of L. maackii. At both sites, understory light levels were lower in plots containing L. maackii. At the asynchronous site, H. macrophyllum received fewer pollinator visits in the presence of L. maackii, suggesting shade from L. maackii reduced visitation to H. macrophyllum. Despite reduced visitation, H. macrophyllum seed set did not differ between treatments. At the synchronous site, H. macrophyllum received more pollinator visits and produced more seeds per flower in the presence of co-flowering L. maackii compared to plots in which L. maackii was absent, and conspecific pollen deposition was positively associated with seed set. Our results support the hypothesis that co-flowering L. maackii shrubs facilitated pollination of H. macrophyllum, thereby mitigating the negative impacts of shade, leading to increased seed production. Phenological overlap appears to influence pollinator-mediated interactions between invasive and native plants and may alter the direction of impact of L. maackii on native plant pollination.     

The ecogenetic link between demography and evolution: can we bridge the gap between theory and data?

Calls to understand the links between ecology and evolution have been common for decades. Population dynamics, i.e. the demographic changes in populations, arise from life history decisions of individuals and thus are a product of selection, and selection, on the contrary, can be modified by such dynamical properties of the population as density and stability. It follows that generating predictions and testing them correctly requires considering this ecogenetic feedback loop whenever traits have demographic consequences, mediated via density dependence (or frequency dependence). This is not an easy challenge, and arguably theory has advanced at a greater pace than empirical research. However, theory would benefit from more interaction between related fields, as is evident in the many near-synonymous names that the ecogenetic loop has attracted. We also list encouraging examples where empiricists have shown feasible ways of addressing the question, ranging from advanced data analysis to experiments and comparative analyses of phylogenetic data.     

Chloroplast biogenesis — Correlation between structure and function

Chloroplast biogenesis is a multistage process leading to fully differentiated and functionally mature plastids. Complex analysis of chloroplast biogenesis was performed on the structural and functional level of its organization during the photoperiodic plant growth after initial growth of seedlings in the darkness. We correlated, at the same time intervals, the structure of etioplasts transforming into mature chloroplasts with the changes in the photosynthetic protein levels (selected core and antenna proteins of PSI and PSII) and with the function of the photosynthetic apparatus in two plant species: bean (Phaseolus vulgaris L.) and pea (Pisum sativum L). We selected these plant species since we demonstrated previously that the mature chloroplasts differ in the thylakoid organization. We showed that the protein biosynthesis as well as photosynthetic complexes formation proceeds gradually in both plants in spite of periods of darkness. We found that both steady structural differentiation of the bean chloroplast and reformation of prolamellar bodies in pea were accompanied by a gradual increase of the photochemical activity in both species. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.     

Pathogenic neisseriae—Interplay between pro-and eukaryotic worlds

The pathogenicNeisseria species constitute a multi-faceted infection model of a highly adapted pathogen-host relationship. Several bacterial and host-cell factors involved in the cellular cross-talk have been recently unraveled. UsingNeisseria gonorrhoeae as a prototype, several structurally variable surface proteins, including pili and Opa proteins, have been revealed as adhesins recognizing distinct host-cell receptors. The Opa proteins, in particular, are important in facilitating interaction with heparan sulfate proteoglycan receptors and members of the CD66 and integrin receptor families. These interactions not only enable the pathogens' anchoring, and penetration into, the human mucosa but also stimulate cellular signaling cascades involving the phosphatidylcholinedependent phospholipase C, acidic sphingomyelinase and protein kinase C in epithelial cells, and Src-related kinases, Rac1, p21-activated kinase and Jun N-terminal kinase in phagocytic cells. Activation of these pathways is essential for the entry and intracellular accommodation of the pathogens but also leads to an early induction of cytokine release, thus priming the immune response. It is believed that detailed knowledge of cellular signaling cascades activated by infection will aid us in applying known and novel interfering drugs, in addition to classical antibiotic therapy, to the therapeutic and prophylactic treatment of persistent or otherwise difficult-to-treat bacterial infections. Presented at the1st International Minisymposium on Cellular Microbiology: Cell Biology and Signalization in Host-Pathogen Interactions, Prague, October 6, 1997.     

Interactions between amyloid β peptide and lipid membranes

The presence of amyloid plaques in the brain is a typical characteristic of Alzheimer's disease (AD). Amyloid plaques are formed from the deposits of aggregated amyloid β peptide (Aβ). The toxicity induced by Aβ aggregates is correlated with Aβ-membrane interactions. The mutual influences between aggregation and membranes are complicated and unclear. In recent years advanced experiments and findings are emerging to give us more detailed information on Aβ-membrane interactions. In this review, we mainly focus on the Aβ-membrane interactions and membrane-induced Aβ structures. The mechanism of Aβ-membrane interactions is also summarized, which provides insights into the prevention and treatment of AD.     

Interaction between Duodenase and α1-Proteinase Inhibitor

The interaction between duodenase, a newly recognized serine proteinase belonging to the small group of Janusfaced proteinases, and ₁-proteinase inhibitor (₁-PI) from human serum was investigated. The stoichiometry of the inhibition was 1.2 mol/mol. The presence of a stable enzyme–inhibitor complex was shown by SDS-PAGE. The mechanism of interaction between duodenase and ₁-PI was shown to be of the suicide type. The equilibrium and inhibition constants are 13 ± 3 nM and (1.9 ± 0.3)·10⁵ M^–1·sec^–1, respectively. Based on the association rate constant of the enzyme–inhibitor complex and localization of duodenase and ₁-PI in identical compartments, ₁-PI is suggested to be a duodenase inhibitor in vivo.     

Phylogenetic relationships between geographically separate Phormidium cyanobacteria: is there a link between north and south polar regions?

We present a phytogeographical comparison between polar (Arctic and Antarctic) and non-polar strains of the cyanobacterial genus Phormidium, which plays a key role in Arctic and Antarctic ecosystems as primary producer. A total of 26 Phormidium strains were studied using a polyphasic approach, 18 from Arctic (Svalbard, Ellesmere Island and Scandinavian Arctic—Abisko) and Antarctic (Antarctic Peninsula—King George and James Ross Island) regions, and 8 from temperate sites (mostly situated in Central Europe). A phylogenetic tree was constructed and compared with similar 16S rRNA sequences retrieved from Genbank. Within the Phormidium autumnale cluster, genetic similarity of 16S rDNA was more related to geographical proximity of strain origin than to morphological similarity. No genetic identity of Phormidium strains from north and south polar regions was found. The cluster Phormidium autumnale apparently belongs to generic entities in which geographical limitation plays a prominent role. However, the cyanobacterial strains found in Europe suggest that the distribution areas of some Phormidium cyanobacteria overlap. The Phormidium autumnale cluster is evidently a very characteristic type and represents an isolated clade within the traditional genus Phormidium. According to morphological features and the structure of trichomes, it is most similar and thus probably belongs to the genus Microcoleus.     

Interactions between metals and alpha-synuclein--function or artefact?

alpha-synuclein is one of a family of proteins whose function remains unknown. This protein has become linked to a number of neurodegenerative disease although its potential causative role in these diseases remains mysterious. In diseases such as Parkinson's disease and Lewy body dementias, alpha-synuclein becomes deposited in aggregates termed Lewy bodies. Also, some inherited forms of Parkinson's diseases are linked to mutations in the gene for alpha-synuclein. Studies have mostly focussed on what causes the aggregation of the protein but, like many amyloidogenic proteins associated with a neurodegenerative disorder, this protein has now been suggested to bind copper. This finding is currently controversial. This review examines the evidence that alpha-synuclein is a copper binding protein and discusses whether this has any significance in determining the function of the protein or whether copper binding is at all necessary for aggregation.     

Competition between α and β globin messenger RNA

Addition to an unfractionated reticulocyte lysate of either α or β globin mRNA or reticulocyte initiation factors does not alter the overall rate of globin synthesis. Addition of β mRNA results in enhanced synthesis of β product and decreased production of α; conversely, addition of α mRNA results in enhanced synthesis of α globin and decreased production of β. We conclude that the amount of any putative α mRNA or β mRNA-specific factor does not normally limit the rate of synthesis of α or β chains; rather, the two mRNAs compete for some non-specific rate-limiting component of chain initiation.     

β-Galactosidase for Distinguishing between Citrobacter and Salmonella

Detection of β-galactosidase with the aid of o-nitrophenyl-β-d-galactopyranoside (ONPG) was examined as a means for distinguishing between Citrobacter and Salmonella. Several factors which influence sensitivity and reliability of the test were studied. A bacteriostat, sodium azide, was included to permit prolonged incubation of weak and negative strains of enteric bacilli. By the procedure described, salmonellae gave negative ONPG tests; all of 171 strains of Citrobacter gave positive tests.