Whole-community facilitation regulates biodiversity on Patagonian rocky shores

Background

Understanding the factors that generate and maintain biodiversity is a central goal in ecology. While positive species interactions (i.e., facilitation) have historically been underemphasized in ecological research, they are increasingly recognized as playing important roles in the evolution and maintenance of biodiversity. Dominant habitat-forming species (foundation species) buffer environmental conditions and can therefore facilitate myriad associated species. Theory predicts that facilitation will be the dominant community-structuring force under harsh environmental conditions, where organisms depend on shelter for survival and predation is diminished. Wind-swept, arid Patagonian rocky shores are one of the most desiccating intertidal rocky shores ever studied, providing an opportunity to test this theory and elucidate the context-dependency of facilitation.

Methodology/Principal Findings

Surveys across 2100 km of southern Argentinean coastline and experimental manipulations both supported theoretical predictions, with 43 out of 46 species in the animal assemblage obligated to living within the matrices of mussels for protection from potentially lethal desiccation stress and predators having no detectable impact on diversity.

Conclusions/Significance

These results provide the first experimental support of long-standing theoretical predictions and reveal that in extreme climates, maintenance of whole-community diversity can be maintained by positive interactions that ameliorate physical stress. These findings have important conservation implications and emphasize that preserving foundation species should be a priority in remediating the biodiversity consequences of global climate change.     

SYTO11 staining vs FISH staining: a comparison of two methods to stain Wolbachia pipientis in cell cultures

Aims: The Aedes albopictus C7‐10 cell line was infected with Wolbachia strains wRi and wAlbB to create C7‐10R and C7‐10B cell lines, respectively. We compared two different methods, fluorescence in situ hybridization staining and SYTO11 staining, to describe these new Wolbachia infections in C7‐10. Methods and Results: Both staining methods were as efficient to stain Wolbachia. A formula was developed to quantify Wolbachia infection. The infection levels in C7‐10B and C7‐10R differed. The live stain SYTO11 was found to be useful to visualize Wolbachia in replicating host cells. Its potential cytotoxic effect at high concentration was investigated. Conclusions: C7‐10 supported two Wolbachia infections, constituting new tools to study Wolbachia–host interactions. The different infection levels suggest that wRi and wAlbB have different requirements for their survival in C7‐10 host cell line. Observation of SYTO11‐stained live cells gave new insights on Wolbachia segregation pattern during host cell mitosis. Significance and Impact of the Study: Wolbachia‐induced phenotypes in their arthropod and worm hosts could potentially be used to control pest populations. However, the mechanisms underlying these phenotypes are difficult to study because of Wolbachia’s intracellular lifestyle. The Wolbachia infections in C7‐10 described here could be used as in vitro models to investigate Wolbachia biology.     

Structure determination of a new fluorescent tricyclic nucleoside from archaebacterial tRNA.

A highly fluorescent nucleoside was detected in enzymatic digests of the extremely thermophilic archaebacterium Sulfolobus solfataricus by combined liquid chromatography-mass spectrometry (LC/MS). Following isolation, the structure was determined primarily by mass spectrometry, to be 3-(beta-D-ribofuranosyl)-4,9-dihydro-4,6,7-trimethyl-9-oxoimidazo[ 1, 2-a]purine (mimG), a new derivative of the Y (wye) nucleoside. The structural assignment was verified by comparison of the base released by acid hydrolysis with the corresponding synthetic base, using mass spectrometry, chromatography, and UV absorption and fluorescence properties. Nucleoside mimG was also detected by LC/MS in hydrolysates of the thermophiles Thermoproteus neutrophilus and Pyrodictium occultum. These results constitute the first finding of a member of the hypermodified Y family of nucleosides in archaebacteria.     

Highly purified human-derived follicle-stimulating hormone (Bravelle®) has equivalent efficacy to follitropin-beta (Follistim ®) in infertile women undergoing in vitro fertilization

Background  

These data compare the efficacy and safety of highly purified human-derived follicle-stimulating hormone (Bravelle(R)) and recombinant follitropin-β (Follistim(R)) in women undergoing in vitro fertilization.     

Cutting edge: nitrogen bisphosphonate-induced inflammation is dependent upon mast cells and IL-1

Nitrogen-containing bisphosphonates (NBPs) are taken by millions for bone disorders but may cause serious inflammatory reactions. In this study, we used a murine peritonitis model to characterize the inflammatory mechanisms of these agents. At dosages comparable to those used in humans, injection of NBPs into the peritoneum caused recruitment of neutrophils, followed by an influx of monocytes. These cellular changes corresponded to an initial increase in IL-1α, which preceded a rise in multiple other proinflammatory cytokines. IL-1R, IL-1α, and IL-1β were required for neutrophil recruitment, whereas other MyD88-dependent signaling pathways were needed for the monocyte influx. Mice deficient in mast cells, but not mice lacking lymphocytes, were resistant to NBP-induced inflammation, and reconstitution of these mice with mast cells restored sensitivity to NBPs. These results document the critical role of mast cells and IL-1 in NBP-mediated inflammatory reactions.     

Inositol 1,4,5-trisphosphate may mediate closure of K+ channels by light and darkness in Samanea saman motor cells

Leaflet movements of Samanea saman (Jacq.) Merr. depend in part upon circadian-rhythmic, light-regulated K⁺ fluxes across the plasma membranes of extensor and flexor cells in opposing regions of the leaf-moving organ, the pulvinus. We previously showed that blue light appears to close open K⁺ channels in flexor protoplasts during the dark period (subjective night) (Kim et al., 1992, Plant Physiol 99: 1532–1539). In contrast, transfer to darkness apparently closes open K⁺ channels in extensor protoplasts during the light period (subjective day) (Kim et al., 1993, Science 260: 960–962). We now report that both these channel-closing stimuli increase inositol 1,4,5-trisphosphate [Ins(1,4,5)P₃] levels in the appropriate protoplasts. If extensor cells are given a pulse of red light followed by transfer to darkness, channels still apparently close (Kim et al. 1993) but changes in Ins(1,4,5)P₃ levels are complex with an initial decrease under red light followed by accumulation. Neomycin, an inhibitor of polyphosphoinositide hydrolysis, inhibits both blue-light-induced Ins(1,4,5)P₃ production and K⁺-channel closure in flexor protoplasts and both dark-induced Ins(1,4,5)P₃ production and K⁺ channel closure in extensor protoplasts. The G-protein activator, mastoparan, mimics blue light and darkness in that it both increases Ins(1,4,5)P₃ levels and closes K⁺ channels in the appropriate cell type at the appropriate time. These results indicate that phospholipase C-catalyzed hydrolysis of phosphoinositides, possibly activated by a G protein, is an early step in the signal-transduction pathway by which blue light and darkness close K⁺ channels in S. saman pulvinar cells.Abbreviations DiS-C₃-(5) 3,3-dipropylthiadicarbocyanine iodide - F measure change in Dis-C₃-(5) fluorescence - F_o initial Dis-C₃-(5) fluorescence - Ins(1,4,5)P₃ inositol 1,4,5-trisphosphate - PtdIns(4,5)P₂ phosphatidylinositol 4,5-bisphosphate - rbc red blood cell Supported by grants from NSF (IBN 9206179 and MCB 9305154) and U.S.-Israel Binational Agricultural Research and Development Fund (IS-1670-90RC) to R.C.C. We thank the University of Connecticut Biotechnology Center for the use of a fluorescent spectrophotometer.     

Cutting edge: ectopic expression of the IL-12 receptor-beta 2 in developing and committed Th2 cells does not affect the production of IL-4 or induce the production of IFN-gamma

The IL-12 receptor-beta 2 (IL-12R beta 2) chain is expressed on Th1 cells and lost upon differentiation to the Th2 phenotype. This has been suggested as the basis for commitment of Th1 cells, because early differentiated Th2 cells do not reverse their phenotype and do not produce IFN-gamma on restimulation in the presence of IL-12. In this study, we ectopically expressed the IL-12 receptor-beta 2 (IL-12R beta 2) bicistronically with enhanced green fluorescent protein by retroviral infection in developing and committed Th2 cells. Restimulation of Th2 cells expressing this ectopic IL-12R beta 2 in the presence of IL-12 led to levels of IL-4 production similar to those in control Th2 cells. The expression of IL-12R beta 2 in Th2 cells did not lead to significant levels of IFN-gamma production, although IL-12-mediated STAT signaling and proliferation were restored. Thus, although the IL-12R beta 2 and IL-12-dependent STAT4 activation are required for Th1 responses, activation of this pathway is not sufficient to restore a Th1 phenotype in developing or committed Th2 cells.     

Stomatal Opening Is Induced in Epidermal Peels of Commelina communis L. by GTP Analogs or Pertussis Toxin

Pretreatment with pertussis toxin or microinjection of guanosine- 5[prime]-(3-thiotriphosphate) (GTP-[gamma]-S) into guard cells in peeled epidermis of Commelina communis L. promoted stomatal opening under subsaturating white light. Guanosine-5[prime]-(2-thiodiphosphate) (GDP-[beta]-S) and adenosine-5[prime]-(3-thiotriphosphate) (ATP-[gamma]-S) did not change stomatal aperture under identical conditions. These results indicate that G proteins may be involved in the regulation of stomatal opening.