The ubiquitous presence of exopolygalacturonase in maize suggests a fundamental cellular function for this enzyme

Exopolygalacturonase (exoPG) is a pectin-degrading enzyme abundant in maize pollen. Using immunochemistry and in situ hybridization it is shown that in addition to its presence in pollen, exoPG is also present in sporophytic tissues, such as the tapetum and mesophyll cells. The enzyme is located in the cytoplasm of pollen and of some mesophyll cells. In other mesophyll cells, the tapetum and the pollen tube, exoPG is located in the cell wall. The measurement of enzyme activity shows that exoPG is ubiquitous in the vegetative organs. These results suggest a general function for exoPG in cell wall edification or degradation. ExoPG is encoded by a closely related multigene family. The regulation of the expression of one of the exoPG genes was analyzed in transgenic tobacco. Reporter GUS activity was detected in anthers, seeds and stems but not in leaves or roots of transgenic plants. This strongly suggests that the ubiquitous presence of exoPG in maize is the result of the expression of different exoPG genes.     

Potent inhibitors of CDK5 derived from roscovitine: Synthesis,biological evaluation and molecular modelling

Cyclin dependent kinase 5 (CDK5) is a serine/threonine kinase belonging to the cyclin dependent kinase (CDK) family. CDK5 is involved in numerous neuronal diseases (including Alzheimer’s or Parkinson’s diseases, stroke, traumatic brain injury), pain signaling and cell migration. In the present Letter, we describe syntheses and biological evaluations of new 2,6,9-trisubstituted purines, structurally related to roscovitine, a promising CDK inhibitor currently in clinical trials (CDK1/Cyclin B, IC₅₀ = 350 nM; CDK5/p25, IC₅₀ = 200 nM). These new molecules were synthesized using an original Buchwald–Hartwig catalytic procedure; several compounds (3j, 3k, 3l, 3e, 4k, 6b, 6c) displayed potent kinase inhibitory potencies against CDK5 (IC₅₀ values ranging from 17 to 50 nM) and showed significant cell death inducing activities (IC₅₀ values ranging from 2 to 9 μM on SH-SY5Y). The docking of the inhibitors into the ATP binding domain of the CDK5 catalytic site highlighted the discriminatory effect of a hydrogen bond involving the CDK5 Lys-89. In addition, the calculated final energy balances for complexation measured for several inhibitors is consistent with the ranking of the IC₅₀ values. Lastly, we observed that several compounds exhibit submicromolar activities against DYRK1A (dual specificity, tyrosine phosphorylation regulated kinase 1A), a kinase involved in Down syndrome and Alzheimer’s disease (3g, 3h, 4m; IC₅₀ values ranging from 300 to 400 nM).     

Simultaneous suppression of multiple genes by single transgenes. Down-regulation of three unrelated lignin biosynthetic genes in tobacco

Many reports now describe the manipulation of plant metabolism by suppressing the expression of single genes. The potential of such work could be greatly expanded if multiple genes could be coordinately suppressed. In the work presented here, we test a novel method for achieving this by using single chimeric constructs incorporating partial sense sequences for multiple genes to target suppression of two or three lignin biosynthetic enzymes. We compare this method with a more conventional approach to achieving the same end by crossing plants harboring different antisense transgenes. Our results indicate that crossing antisense plants is less straightforward and predictable in outcome than anticipated. Most progeny had higher levels of target enzyme activity than predicted and had lost the expected modifications to lignin structure. In comparison, plants transformed with the chimeric partial sense constructs had more consistent high level suppression of target enzymes and had significant changes to lignin content, structure, and composition. It was possible to suppress three target genes coordinately using a single chimeric construct. Our results indicate that chimeric silencing constructs offer great potential for the rapid and coordinate suppression of multiple genes on diverse biochemical pathways and that the technique therefore deserves to be adopted by other researchers.     

Brown‐midrib maize (bm1) – a mutation affecting the cinnamyl alcohol dehydrogenase gene

Brown-midrib (bm) mutants of maize have modified lignin of reddish-brown colour. Although four independent bm loci are known, only one of the mutant genes has been previously identified. We report here that maize bm1, one of the less characterised mutants, shows severely reduced CAD activity in lignified tissues, resulting in the production of a modified lignin. Both the total lignin content and the structure of the polymer are altered by the mutation. We further describe the isolation and characterisation of the maize CAD cDNA and mapping of the CAD gene. CAD maps very closely to the known location of bm1 and co-segregates with the bm1 locus in two independent recombinant inbred populations. These data strongly support the premise that maize bm1 directly affects expression of the CAD gene.     

Phylodynamics and human-mediated dispersal of a zoonotic virus

Understanding the role of humans in the dispersal of predominantly animal pathogens is essential for their control. We used newly developed Bayesian phylogeographic methods to unravel the dynamics and determinants of the spread of dog rabies virus (RABV) in North Africa. Each of the countries studied exhibited largely disconnected spatial dynamics with major geopolitical boundaries acting as barriers to gene flow. Road distances proved to be better predictors of the movement of dog RABV than accessibility or raw geographical distance, with occasional long distance and rapid spread within each of these countries. Using simulations that bridge phylodynamics and spatial epidemiology, we demonstrate that the contemporary viral distribution extends beyond that expected for RABV transmission in African dog populations. These results are strongly supportive of human-mediated dispersal, and demonstrate how an integrated phylogeographic approach will turn viral genetic data into a powerful asset for characterizing, predicting, and potentially controlling the spatial spread of pathogens.     

Caractérisation probable du Sinémurien près de Telouat (Haut-Atlas,Maroc): Datation palynologique

The liassic beds of the High-Atlas of Marrakech are rarely fossiliferous so all paleontological discoveries must be reported in order to give more biostratigraphical precisions for the interpretations of the sourcestrata basin. Palynological investigations in section composed of marl and dolomites with gypsum yield assemblages which the overall composition is characterized by the general dominance of Corollina in combination with relatively rare occurence of others nonsaccate pollen grains. Because the comparison of the associations previously described from the Lower Jurassic of Morocco and Sahara and the fact that the richness of Corollina has no stratigraphical value, the assemblages from the Telouat' section can be reasonably regarded to be indicative of a Sinemurian age.     

McRAPD as a new approach to rapid and accurate identification of pathogenic yeasts

Despite advances in antifungal prophylaxis and therapy, morbidity and mortality incurred by yeasts remain a significant burden. As pathogenic yeast species vary in their susceptibilities to antifungal agents, clinical microbiology laboratories face an important challenge to identify them rapidly and accurately. Although a vast array of phenotyping and genotyping methods has been developed, these are either unable to cover the whole spectrum of potential yeast pathogens or can do this only in a rather costly or laborious way. Random amplified polymorphic DNA (RAPD) fingerprinting was repeatedly demonstrated to be a convenient tool for species identification in pathogenic yeasts. However, its wider acceptance has been limited mainly due to special expertise and software needed for analysis and comparison of the resulting banding patterns. Based on a pilot study, we demonstrate here that a simple and rapid melting curve analysis of RAPD products can provide data for identification of five of the most medically important Candida species. We have termed this new approach melting curve of random amplified polymorphic DNA (McRAPD) to emphasize its rapidity and potential for automation, highly desirable features for a routine laboratory test.     

Secreted aspartate proteinases,a virulence factor of<Emphasis Type="Italic">Candida</Emphasis> spp.: Occurrence among clinical isolates

Production of secreted aspartate proteinases was determined in a set of 646 isolates of Candida and non-Candida yeast species collected from 465 patients of the University Hospital in Olomouc (Czechia) in the period 1995-2002, and Candida samples obtained from 64 healthy volunteers using solid media developed for this purpose. Using random amplified polymorphic DNA analysis (RAPD) 79 Candida isolates from blood were analyzed to show potential relationships between clustering of the fingerprints and extracellular proteolytic activity of these strains. C. albicans, C. tropicalis and C. parapsilosis possess always proteolytic activity while non-Candida species did not display any proteolysis. A tight relationship between fingerprints and extracellular proteolysis in the Candida isolates was not shown. A remarkable consistency between fingerprint clusters and proteolysis occurred in a subset of C. parapsilosis samples. Suboptimal pH of the growth medium was shown to facilitate the investigation of potential co-incidence of genotypic and phenotypic traits.