Cell-to-cell communication in plants, animals, and fungi: a comparative review

Cell-to-cell communication is a prerequisite for differentiation and development in multicellular organisms. This communication has to be tightly regulated to ensure that cellular components such as organelles, macromolecules, hormones, or viruses leave the cell in a precisely organized way. During evolution, plants, animals, and fungi have developed similar ways of responding to this biological challenge. For example, in higher plants, plasmodesmata connect adjacent cells and allow communication to regulate differentiation and development. In animals, two main general structures that enable short- and long-range intercellular communication are known, namely gap junctions and tunneling nanotubes, respectively. Finally, filamentous fungi have also developed specialized structures called septal pores that allow intercellular communication via cytoplasmic flow. This review summarizes the underlying mechanisms for intercellular communication in these three eukaryotic groups and discusses its consequences for the regulation of differentiation and developmental processes.     

Low level inhalation experiments with four different cadmium compounds in rats†

This long‐term inhalation study was designed to describe the toxicity and the carcinogenic risk from Cd compounds because it had been shown from former long‐term inhalation studies that cadmium choloride induced primary lung tumors in Wistar rats. It was therefore logical to examine whether other cadmium compounds to which human beings are more frequently exposed have also carcinogenic potency. In a long‐term inhalation study cadmium aerosols consisting of cadmium chloride (CdCl₂), cadmium oxide (CdO) as dusts and fumes, cadmium sulfate (CdSO₄), cadmium sulfide (CdS) and a combination of cadmium oxide/zinc oxide were used. Wistar rats were continuously exposed in inhalation chambers for 18 months 22 hrs a day or for 40 hrs a week. The studies will be terminated at the mean survival life time of the species. The aerosols were generated by several different systems. The particles of the cadmium aerosols have the average mass medium diameters in the range from 0.2 to 0.5 μm.     

Prostaglandin F2α facilitates female mating behavior based on male performance

Hormones play an important role in the regulation of reproductive behavior. Here, we examined the effects of the fatty acid derivative prostaglandin F2α (PGF2) on female sexual behavior as well as the interaction between PGF2-induced mating behavior with male courtship display in the lek-breeding African cichlid fish, Astatotilapia burtoni. In a two-way choice paradigm, we found that nonreproductive females preferred to associate with smaller, less aggressive males over larger, more aggressive males. However, PGF2-treated females dramatically reversed their preference to larger males. In a second experiment, PGF2 treatment dramatically increased sexual behavior in nonreproductive females as measured by time spent in the bower of the stimulus male, even when the female and the stimulus male were separated by a transparent divider. This effect was even more pronounced when the stimulus males were exposed to the putative female pheromone 17α,20β-progesterone (17α,20β-P). Under full-contact conditions, only PGF2-treated females visited a stimulus male’s bower, where they even displayed circling behavior usually only seen during spawning. Interestingly, male performance prior to PGF2 treatment predicted female sexual response. Our study demonstrates the importance of PGF2 in the control of female reproductive behavior in interaction with male performance.     

Long-term monitoring of environmental change in German towns through the use of lichens as biological indicators: comparison between the surveys of 1970, 1980, 1985, 1995, 2005 and 2010 in Wetzlar and Giessen

Background

In the years 1970, 1980, 1985, 1995, 2005 and 2010, lichen mapping in the towns of Wetzlar and Giessen in Hesse was performed. The aim was to show the effects of immission load. Despite the application of modified test methods during the study period, the results can still be compared directly because they could be adapted to the requirements of the guidelines of the Association of German Engineers. Even the earlier study results could be interpreted partly within the scope of the guidelines. Parallel to the lichen mapping, comparative examinations of pH on tree bark were carried out.

Results

In both towns, the pH of the tree bark has been increasing continuously, presently almost reaching pre-industrial values. The increase was stronger in Wetzlar than in Giessen. In 1970, the lichen vegetation showed a complete depletion. Since then the number of species has risen significantly. This development happened faster and more intensely in Wetzlar. The comparison of the lichen vegetation between 1970 and 2010 also shows an increased existence of species that are favored by hypertrophic air contaminants. In the 2010 survey, some species considered as being promoted by global warming were found for the first time.

Conclusions

The increase of the bark pH can be explained by the decreasing acid pollution, primarily SO₂. This is also assumed to be the main cause for the increasing number of lichen species. An explanation for Wetzlar's advantage is that the acid pollutants had been neutralized by a local industrial emittent of lime dust. With the reduction of dust emissions in Wetzlar due to the installation of filters, the bark pH in both towns steadily converged in the reference period. An examination of pre-industrial lichen studies shows that in both towns the original state of lichen vegetation has not been restored yet.     

Assessment of regional capabilities for agricultural coexistence with genetically modified maize

Background

The coexistence of agricultural production with and without the use of genetically modified (GV) crops is supposed to be made possible in Germany by regulations, which include minimal distances of GV-fields to potentially susceptible crop fields and habitats. To explore the impact of these regulations on region specific coexistence potentials, we broadened the applicability of an existing method for the simulation of the spatial distribution of arable fields cropped with conventional, organic and GV-maize. We used simulations which combine a variety of minimum distances of GV-maize fields to assess regional specific options and limitations for coexistence.

Results

An existing method was extended to be applicable for different spatial scales, from the large (e.g. Federal State) to small (e.g. municipality). Input data consisted of cropping statistics, geometry of arable fields and protected areas. Scenarios of cropping situations included various minimal distances between GV-maize fields and protected areas and various proportions of maize within the areas. The results of the simulations represent possible distribution patterns of non-GV and GV-maize fields as well as the size of the remaining area in which additional GV-maize can be grown without violating the minimal distance rules. As suspected, increasing proportions of GV-maize and increasing minimal distances lower the areas suitable for additional GV-maize. However, the relation between the area of GV-maize grown and those suitable for GV-maize cultivation varied between the scenarios. Moreover, the variability between the municipalities was even more evident, due to varying landscape structure (proportion of maize, the ratio total arable land to maize, proportion of protected areas). Areas with high proportions of GV-maize, of protected areas and of maize could be problematical for coexistence. We discuss these parameters with regard to other coexistence studies.

Conclusions

Our method is suitable to simulate the spatial distribution of fields cultivated with GV-crops and non-GV-crops on various scales. Simulations on the scale of a Federal State reveals those areas, in which coexistence could be problematical. Simulations on a county scale, however, allow more insight into options and restrictions for coexistence in relation to landscape structural characteristics, which also can be transferred to larger scales. On the scale of municipalities simulations can help to analyse the limits of coexistence in areas of high conflict potential, moreover this level is more realistic with regard to practical agricultural decisions on the farm level.

Zusammenfassung

Hintergrund

Die Koexistenz verschiedener landwirtschaftlicher Produktionsformen ?C mit und ohne Anbau von gentechnisch ver?nderten Pflanzen (GVO) ?C soll durch gesetzlich fixierte Regeln erm?glicht werden, die unter anderem die Mindestabst?nde von GVO-Anbaufl?chen zu potenziell empfindlichen anderen Ackerfl?chen und Biotopen festlegen. Hier wurde eine Methode weiterentwickelt zur Simulation der r?umlichen Verteilung der Anbaufl?chen von konventionellem, ?kologischem und GV-Mais um regionsspezifische Koexistenzpotenziale von gentechnisch ver?ndertem Mais, sowie potenzielle Konfliktgebiete zu identifizieren.

Ergebnisse

Eine für Brandenburg entwickelte GIS-Simulationsmethode wurde durch die Verwendung fl?chendeckend vorhandener Daten so erweitert, dass sie bundesweit übertragbar ist und auf unterschiedlichen r?umlichen Skalenebenen angewandt werden kann, von gro?r?umig (Bundesland) bis lokal (Gemeinde). Als Eingangsdaten wurden Anbaustatistiken sowie Geometrien der Ackerfl?chen und von FFH- und Naturschutzgebieten verwendet. In den Szenarien wurden Abstandsregelungen zwischen Maisanbaufl?chen und zu Schutzgebieten und der GV-Maisanteil variiert. Die Ergebnisse der Simulation sind m?gliche r?umliche Verteilungen von Nicht-GV-Mais und GV-Mais sowie die potenziell für den Anbau von GV-Mais zur Verfügung stehende Fl?che. Mit zunehmendem GV-Maisanteil und Mindestabst?nden zu Schutzgebieten wird die für den GV-Mais zur Verfügung stehende Fl?che st?rker ausgesch?pft. Der Anteil des GV-Mais an der potenziell für den Anbau von GV-Mais zur Verfügung stehenden Fl?che variierte zwischen den Szenarien, und noch st?rker jedoch regional zwischen den Landkreisen, verursacht durch deren verschiedene agrar- und landschaftsstrukturelle Ausstattung (Maisanbauanteil, Verh?ltnis Ackerlandsanteil/Maisanbauanteil, Schutzgebietsanteil). Ein r?umliches Konfliktpotenzial bei der Umsetzung der Koexistenz ist in Gebieten hohen Nutzungsdrucks zu erwarten, d.h. in denen sowohl der Maisanbauanteil an der Ackerfl?che und der Anbauanteil von GV-Mais, als auch der Schutzgebietsanteil hoch sind. Diese Faktoren werden diskutiert in Bezug zu Ergebnissen weiterer Koexistenzstudien.

Schlussfolgerungen

Die vorgestellte Methode ist geeignet, die r?umliche Verteilung des Anbaus von Nicht-GV-Mais und GV-Mais auf unterschiedlichen Skalenebenen zu simulieren: Die Ebene eines Bundeslandes liefert Hinweise auf Gebiete, in denen die Koexistenz problematisch sein k?nnte und kann als Grundlage weiterer Berechnungen, wie zum Beispiel der Modellierung von Genflüssen auf Landesebene dienen. Die Simulation auf der Ebene eines Landkreises oder einer Gemeinde erm?glicht genauere Aussagen über die M?glichkeiten und Grenzen der Koexistenz. Auf der Ebene der Landkreise k?nnen z.B. unterschiedliche agrar- und landschaftsstrukturelle Situationen untersucht und für eine nachfolgende Regionalisierung angewandt werden. Die Ebene der Gemeinden erlaubt die Analyse der Grenzen der Koexistenz für Gebiete mit h?herem r?umlichen Konfliktpotenzial. Simulationen auf lokaler Ebene erscheinen darüber hinaus n?her an den Entscheidungsm?glichkeiten der landwirtschaftlichen Praxis.     

How maize root volatiles affect the efficacy of entomopathogenic nematodes in controlling the western corn rootworm?

Because the ferocious maize pest Diabrotica virgifera virgifera LeConte can adapt to all currently used control strategies, focus has turned to the development of novel, more sustainable control methods, such as biological control using entomopathogenic nematodes (EPN). A good understanding of the biology and behaviour of these potential control agents is essential for their successful deployment. Root systems of many maize varieties emit (E)-β-caryophyllene (EβC) in response to feeding by larvae of the beetle D. v. virgifera. This sesquiterpene has been shown to attract certain species of EPN, thereby enhancing their control potential. In this study, we tested the effect of this root-produced volatile on the field efficacy of the three EPN Heterorhabditis bacteriophora, Heterorhabditis megidis and Steinernema feltiae against D. v. virgifera larvae in southern Hungary. By comparing beetle emergence and root damage for two maize varieties, one that emits EβC and one that does not, it was found that root protection by H. megidis and S. feltiae was higher on the emitting variety, but this was not the case for H. bacteriophora. Overall, all three nematode species showed good control potential. We conclude that, if properly applied and in combination with the right maize variety, the release of these nematodes can be as effective as other control methods.     

Trophic role of small cyclopoid copepod nauplii in the microbial food web: a case study in the coastal upwelling system off central Chile

Copepod grazing impact on planktonic communities has commonly been underestimated due to the lack of information on naupliar feeding behaviour and ingestion rates. That is particularly true for small cyclopoid copepods, whose nauplii are mainly in the microzooplankton size range (<200 μm). The trophic role of Oithona spp. nauplii was investigated off Concepción (central Chile, ~36°S) during the highly productive upwelling season, when maximum abundances of these nauplii were expected. Diet composition, ingestion rates, and food-type preferences were assessed through grazing experiments with different size fractions of natural planktonic assemblages (<3, <20, <100, and <125 μm) and cultures of the nanoflagellate Isochrysis galbana. When the Oithona spp. nauplii were offered a wide range of size fractions as food (pico- to microplankton), they mostly ingested small (2–5 μm) nanoflagellates (5–63 × 10³ cells nauplius⁻¹ day⁻¹). No ingestion on microplankton was detected, and picoplankton was mainly ingested when it was the only food available. Daily carbon (C) uptake by the nauplii ranged between 28 and 775 ng C nauplius⁻¹, representing an overall mean of 378% of their body C. Our relatively high ingestion rate estimates can be explained by methodological constraints in previous studies on naupliar feeding, including those dealing with “over-crowding” and “edge” effects. Overall, the grazing impact of the Oithona spp. nauplii on the prey C standing stocks amounts up to 21% (average = 13%) for picoplankton and 54% (average = 28%) for nanoplankton. These estimates imply that the nauplii of the most dominant cyclopoid copepods exert a significant control on the abundances of nanoplankton assemblages and, thereby, represent an important trophic link between the classical and microbial food webs in this coastal upwelling system.     

Spatial and temporal variation in distribution and protein ubiquitination for <Emphasis Type="Italic">Mytilus</Emphasis> congeners in the California hybrid zone

Along the west coast of North America, the invasive mussel Mytilus galloprovincialis and a native congener M. trossulus overlap in range and compete for habitat in an extensive hybrid zone along central California. The two species have been shown to exhibit differential abiotic tolerances in laboratory studies, yet little is known about how such tolerances affect spatial and temporal patterns of geographic distribution, particularly in areas of competition. We examined distributions of the two congeners and their hybrids in neighboring intertidal and subtidal habitats in Bodega Bay, CA over 2 years, and compared shell length and seasonal ubiquitin (Ub) conjugates to estimate protein turnover and physiological stress for the species at each site. The two species were spatially segregated, with M. galloprovincialis dominating the subtidal habitat, and M. trossulus constituting a majority of the intertidal mussel population. Hybrid individuals appeared in low numbers at both sites. For each habitat, there was no statistical difference between shell lengths of M. galloprovincialis and hybrids but M. trossulus mussels were statistically smaller than the other two. In regards to physiological performance, ubiquitin conjugate values showed different seasonal cycles for the two species, suggesting different periods of peak environmental stress. The highest levels of Ub-conjugated proteins were observed in winter for M. galloprovincialis and in summer for M. trossulus, consistent with the respective range edges for their distributions since Bodega Bay is near the northern range edge of the invader and the southern edge of the native species. These findings suggest that future assessments of Mytilus populations along the California coast may need to consider vertical distributions and seasonal cycles as part of monitoring and research activities.