Local adaptation to temperature in populations and clonal lineages of the Irish potato famine pathogen Phytophthora infestans

Environmental factors such as temperature strongly impact microbial communities. In the current context of global warming, it is therefore crucial to understand the effects of these factors on human, animal, or plant pathogens. Here, we used a common‐garden experiment to analyze the thermal responses of three life‐history traits (latent period, lesion growth, spore number) in isolates of the potato late blight pathogen Phytophthora infestans from different climatic zones. We also used a fitness index (FI) aggregating these traits into a single parameter. The experiments revealed patterns of local adaptation to temperature for several traits and for the FI, both between populations and within clonal lineages. Local adaptation to temperature could result from selection for increased survival between epidemics, when isolates are exposed to more extreme climatic conditions than during epidemics. We also showed different thermal responses among two clonal lineages sympatric in western Europe, with lower performances of lineage 13_A2 compared to 6_A1, especially at low temperatures. These data therefore stress the importance of thermal adaptation in a widespread, invasive pathogen, where adaptation is usually considered almost exclusively with respect to host plants. This must now be taken into account to explain, and possibly predict, the global distribution of specific lineages and their epidemic potential.     

Spindle assembly checkpoint genes reveal distinct as well as overlapping expression that implicates MDF-2/Mad2 in postembryonic seam cell proliferation in Caenorhabditis elegans

Background

The spindle assembly checkpoint (SAC) delays anaphase onset by inhibiting the activity of the anaphase promoting complex/cyclosome (APC/C) until all of the kinetochores have properly attached to the spindle. The importance of SAC genes for genome stability is well established; however, the roles these genes play, during postembryonic development of a multicellular organism, remain largely unexplored.

Results

We have used GFP fusions of 5' upstream intergenic regulatory sequences to assay spatiotemporal expression patterns of eight conserved genes implicated in the spindle assembly checkpoint function in Caenorhabditis elegans. We have shown that regulatory sequences for all of the SAC genes drive ubiquitous GFP expression during early embryonic development. However, postembryonic spatial analysis revealed distinct, tissue-specific expression of SAC genes with striking co-expression in seam cells, as well as in the gut. Additionally, we show that the absence of MDF-2/Mad2 (one of the checkpoint genes) leads to aberrant number and alignment of seam cell nuclei, defects mainly attributed to abnormal postembryonic cell proliferation. Furthermore, we show that these defects are completely rescued by fzy-1(h1983)/CDC20, suggesting that regulation of the APC/C^CDC20 by the SAC component MDF-2 is important for proper postembryonic cell proliferation.

Conclusion

Our results indicate that SAC genes display different tissue-specific expression patterns during postembryonic development in C. elegans with significant co-expression in hypodermal seam cells and gut cells, suggesting that these genes have distinct as well as overlapping roles in postembryonic development that may or may not be related to their established roles in mitosis. Furthermore, we provide evidence, by monitoring seam cell lineage, that one of the checkpoint genes is required for proper postembryonic cell proliferation. Importantly, our research provides the first evidence that postembryonic cell division is more sensitive to SAC loss, in particular MDF-2 loss, than embryonic cell division.     

Context-dependent memory: colour versus odour

An olfactory stimulus and a visual stimulus were employed in a context- dependent memory study using a prose passage as the to-be-remembered item. Ninety-five university students (aged 17-35 years) learned the passage of prose in the presence of one of the stimuli and were then asked to recall the passage with the original context either reinstated or not reinstated. The results revealed a significant context-dependent memory effect for the olfactory cue but not for the visual cue. They demonstrate support for the effectiveness of odours as context cues and it is suggested that context-dependent memory processes may underlie the formation and retrieval of odour-evoked autobiographical memories.      

SdFFF monitoring of cellular apoptosis induction by diosgenin and different inducers in the human 1547 osteosarcoma cell line

Apoptosis is one of the most important phenomena of cellular biology. Sedimentation field flow fractionation (SdFFF) has been described as an effective tool for cell separation, respecting integrity and viability. Because SdFFF takes advantage of intrinsic properties of eluted cells (size, density, shape or rigidity), we investigated the capacity of SdFFF in monitoring the early and specific biophysical modifications which occurred during cellular apoptosis induction. Then, we used, as an in vitro cellular apoptosis model, the association between human 1547 osteosarcoma cells and diosgenin, a plant steroid known to induce apoptosis. Four other molecules were studied: hecogenin, tigogenin, staurosporine and MG132. Our results demonstrated a correlation between SdFFF elution profile changes (peak shape modification and retention ratio evolution) and effective apoptosis induction. For the first time, we demonstrated that SdFFF could be used to monitor apoptosis induction as early as 6 h incubation, suggesting different applications such as screening series of molecules to evaluate their ability to induce apoptosis, or sorting apoptotic cells to study apoptosis pathway.     

Pt(II) and Ag(I) complexes with acesulfame: Crystal structure and a study of their antitumoral, antimicrobial and antiviral activities

Two new complexes of platinum(II) and silver(I) with acesulfame were synthesized. Acesulfame is in the anionic form acesulfamate (ace). The structures of both complexes were determined by X-ray crystallography. For K₂[PtCl₂(ace)₂] the platinum atom is coordinated to two Cl⁻ and two N-acesulfamate atoms forming a trans-square planar geometry. Each K⁺ ion interacts with two oxygen atoms of the S(O)₂ group of each acesulfamate. For the polymeric complex [Ag(ace)]_n the water molecule bridges between two crystallographic equivalent Ag1 atoms which are related each other by a twofold symmetry axis. Two Ag1 atoms, related to each other by a symmetry centre, make bond contact with two equivalent oxygen atoms. These bonds give rise to infinite chains along the unit cell diagonal in the ac plane. The in vitro cytotoxic analyses for the platinum complex using HeLa (human cervix cancer) cells show its low activity when compared to the vehicle-treated cells. The Ag(I) complex submitted to in vitro antimycobacterial tests, using the Microplate Alamar Blue (MABA) method, showed a good activity against Mycobacterium tuberculosis, responsible for tuberculosis, with a minimal inhibitory concentration (MIC) value of 11.6 μM. The Ag(I) complex also presented a promising activity against Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive (Enterococcus faecalis) microorganisms. The complex K₂[PtCl₂(ace)₂] was also evaluated for antiviral properties against dengue virus type 2 (New Guinea C strain) in Vero cells and showed a good inhibition of dengue virus type 2 (New Guinea C strain) replication at 200 μM, when compared to vehicle-treated cells.