Microsatellite stability in the plant pathogen Botrytis cinerea after exposure to different selective pressures

The stability of microsatellite markers was investigated in the spore-producing fungus Botrytis cinerea exposed to four growth conditions. This knowledge is essential in order to differentiate mutations from genetic exchanges or recombination in population genetics studies. It is also important when using strains from collections that need to be regularly propagated on medium. Successive spore generations of four isolates of the fungus were realised in plates on different agar media: a nutrient-rich medium, a nutrient-poor medium, a medium supplemented with the antibiotic pyrrolnitrin and a medium supplemented with the fungicide iprodione. The stability of nine microsatellite markers was studied by comparing the molecular pattern obtained between the wild type parent strains and the final generations obtained. The results showed that, despite the phenotypic changes observed in some generations, no changes were observed in the allele size at nine microsatellite loci whatever the selective pressure endured by the fungus. This is the first study that reveals long-term stability of microsatellite markers of a spore-producing fungus exposed to different stresses.     

Notch signaling in intestinal homeostasis across species: the cases of Drosophila, Zebrafish and the mouse

Notch signaling has been recently shown to have a fundamental role in stem cell maintenance and control of proper homeostasis in the intestine of different species. Here, we briefly review the current literature on Notch signals in the intestine of Drosophila, Zebrafish and the mouse, and try to highlight conserved and divergent Notch functions across species. Notch signals show a remarkably conserved role in skewing cell fate choices in intestinal lineages throughout evolution. Genetic analysis demonstrates that loss of Notch signaling invariably leads to increased numbers of secretory cells and loss of enterocytes, while gain of Notch function will completely block secretory cell differentiation. Finally, we discuss the potential contribution of Notch signaling to the initiation of colorectal cancer by controlling the maintenance of the undifferentiated state of intestinal neoplastic cells and speculate on the therapeutic consequences of affecting cancer stem cells.     

Features of air masses associated with the deposition of Pseudomonas syringae and Botrytis cinerea by rain and snowfall

Clarifying the role of precipitation in microbial dissemination is essential for elucidating the processes involved in disease emergence and spread. The ecology of Pseudomonas syringae and its presence throughout the water cycle makes it an excellent model to address this issue. In this study, 90 samples of freshly fallen rain and snow collected from 2005–2011 in France were analyzed for microbiological composition. The conditions favorable for dissemination of P. syringae by this precipitation were investigated by (i) estimating the physical properties and backward trajectories of the air masses associated with each precipitation event and by (ii) characterizing precipitation chemistry, and genetic and phenotypic structures of populations. A parallel study with the fungus Botrytis cinerea was also performed for comparison. Results showed that (i) the relationship of P. syringae to precipitation as a dissemination vector is not the same for snowfall and rainfall, whereas it is the same for B. cinerea and (ii) the occurrence of P. syringae in precipitation can be linked to electrical conductivity and pH of water, the trajectory of the air mass associated with the precipitation and certain physical conditions of the air mass (i.e. temperature, solar radiation exposure, distance traveled), whereas these predictions are different for B. cinerea. These results are pertinent to understanding microbial survival, emission sources and atmospheric processes and how they influence microbial dissemination.     

Human testicular angiotensin-converting enzyme is a mixture of two molecular weight forms. Only one is similar to the seminal plasma enzyme

Two molecular weight (Mr) forms of angiotensin-converting enzyme are present in human testis. Both the high Mr 140,000 form and the low Mr 90,000 form are catalytically similar but immunologically distinct. After isoelectric focusing, the profile of sialylated Mr 140,000 isozymes resembled that of seminal plasma converting enzyme, whereas the nonsialylated Mr 90,000 isozymes were distinct. These data suggest that the Mr 140,000 testicular converting enzyme may be a source of converting enzyme in seminal plasma.     

Further Characterization of Protein Secondary Structures in Purple Membrane by Circular Dichroism and Polarized Infrared Spectroscopies

The conformation and the orientation of the protein secondary structures in purple membrane was analyzed by infrared absorption and linear dichroism of oriented membranes as well as by UV circular dichroism of bacteriorhodopsin in intact purple membrane and in lipid vesicles. A large amount (74 ± 5%) of transmembrane α-helices is detected with no significant contribution of β-sheet strands running perpendicular to the membrane plane. Thus, these data do not support the recent structural model proposed by Jap et al. (Biophys. J. 1983, 43:81-89).     

Junctional adhesion molecule C (JAM-C) dimerization aids cancer cell migration and metastasis

Most cancer deaths result from metastasis, which is the dissemination of cells from a primary tumor to distant organs. Metastasis involves changes to molecules that are essential for tumor cell adhesion to the extracellular matrix and to endothelial cells. Junctional Adhesion Molecule C (JAM-C) localizes at intercellular junctions as homodimers or more affine heterodimers with JAM-B. We previously showed that the homodimerization site (E66) in JAM-C is also involved in JAM-B binding. Here we show that neoexpression of JAM-C in a JAM-C-negative carcinoma cell line induced loss of adhesive property and pro-metastatic capacities. We also identify two critical structural sites (E66 and K68) for JAM-C/JAM-B interaction by directed mutagenesis of JAM-C and studied their implication on tumor cell behavior. JAM-C mutants did not bind to JAM-B or localize correctly to junctions. Moreover, mutated JAM-C proteins increased adhesion and reduced proliferation and migration of lung carcinoma cell lines. Carcinoma cells expressing mutant JAM-C grew slower than with JAM-C WT and were not able to establish metastatic lung nodules in mice. Overall these data demonstrate that the dimerization sites E66-K68 of JAM-C affected cell adhesion, polarization and migration and are essential for tumor cell metastasis.     

Genetic structure of natural populations of Nitrobacter in an aquatic environment

Nitrification has been essentially studied as a chemical process and the studies of the microbial population have been slightly worked out. This work constitutes a first attempt to study the diversity of Nitrobacter strains with the aim of working out the genetic structure of natural populations. The Nitrobacter population structure was compared between freshwater and sediments of the same lake. Nitrobacter isolates were identified and characterized by DNA/DNA hybridization, restriction pattern of rRNA genes, PCR/RFLP analysis of the ribosomal intergenic spacer and plasmid patterns. It was shown that this lake population was split into 3 subpopulations: a specific freshwater subpopulation, a specific sediment subpopulation and a nonspecific one. A 60 MDa plasmid was detected in 3,3% of freshwater isolates. A 37 MDa plasmid was detected in 59% of sediments isolates. This 37 MDa plasmid was not associated with a genomic group, but associated with a localization: the sediments. These results suggest that this 37 MDa plasmid could be implicated in the adaptation to sediment environment.