MgSlt2, a cellular integrity MAP kinase gene of the fungal wheat pathogen Mycosphaerella graminicola, is dispensable for penetration but essential for invasive growth

Among expressed sequence tag libraries of Mycosphaerella graminicola isolate IPO323, we identified a full-length cDNA clone with high homology to the mitogen-activated protein (MAP) kinase Slt2 in Saccharomyces cerevisiae. This MAP kinase consists of a 1242-bp open reading frame, and encodes a 414-amino-acid protein. We designated this homolog MgSlt2, generated MgSlt2 knockout strains in M. graminicola isolate IPO323, and found several altered phenotypes in vitro as well as in planta. In yeast glucose broth, MgSlt2 disruptants showed a defective polarized growth in the tip cells upon aging, causing substantial local enlargements culminating in large swollen cells containing two to four nuclei. The MgSlt2 disruptants showed a significantly increased sensitivity to several fungicides, including miconazole (2x), bifonazole (>4x), imazalil (5x), and cyproconazole (10x), and were hypersensitive to glucanase. Unlike the wild type, MgSlt2 disruptants did not produce aerial mycelia and did not melanize on potato dextrose agar. Although cytological analysis in planta showed normal penetration of wheat stomata by the germ tubes of the MgSlt2 disruptants, subsequently formed hyphal filaments frequently were unable to branch out and establish invasive growth resulting in highly reduced virulence, and prevented pycnidia formation. Therefore, we conclude that MgSlt2 is a new pathogenicity factor in M. graminicola.     

The magnum-isthmus junction of the fowl oviduct participates in the formation of the avian-type shell membrane

Avian eggs possess a shell membrane in the shape of an asymmetrical ellipsoid and with a limiting membrane that is a smooth layer of homogeneous, dense materials. We describe the role of the magnum-isthmus junction (MIJ) of the oviduct in the formation of the avian-type shell membrane in the domestic fowl Gallus domesticus. The narrow width of the lumen at the MIJ indirectly participates in the determination of the asymmetrical ellipsoid shape of eggs that are encased by the egg-white layer and subsequently by the peri-albumen layer (PL) and the shell membrane. The PL reacts with Alcian blue and exists between the egg white and the limiting membrane. It is added to the ovulating egg at the MIJ and covers the outermost surface of the egg-white layer. The function of the PL is to provide a smooth surface by covering the irregular surface of the egg-white layer. The materials of the PL consist of an Alcian blue-positive polysaccharide (or glycoprotein) of 240 kDa and five proteins of 135, 116, 72, 49, and 46 kDa. The isolated materials have an affinity to bind with the egg-white mass. An antiserum against quail PL materials stains the domestic fowl PL and secretory cells of the luminal epithelium at the MIJ, and cross-reacts with the molecules of 240, 135, and 116 kDa.     

Molecular markers in management of ex situ PGR – A case study

Worldwide germplasm collections contain about 7.4 million accessions of plant genetic resources for food and agriculture. One of the 10 largest ex situ genebanks of our globe is located at the Leibniz Institute of Plant Genetics and Crop Plant Research in Gatersleben, Germany. Molecular tools have been used for various gene bank management practices including characterization and utilization of the germplasm. The results on genetic integrity of long-term-stored gene bank accessions of wheat (self-pollinating) and rye (open-pollinating) cereal crops revealed a high degree of identity for wheat. In contrast, the out-pollinating accessions of rye exhibited shifts in allele frequencies. The genetic diversity of wheat and barley germplasm collected at intervals of 40 to 50?years in comparable geographical regions showed qualitative rather than a quantitative change in diversity. The inter- and intraspecific variation of seed longevity was analysed and differences were detected. Genetic studies in barley, wheat and oilseed rape revealed numerous QTL, indicating the complex and quantitative nature of seed longevity. Some of the loci identified were in genomic regions that co-localize with genes determining agronomic traits such as spike architecture or biotic and abiotic stress response. Finally, a genome-wide association mapping analysis of a core collection of wheat for flowering time was performed using diversity array technology (DArT) markers. Maker trait associations were detected in genomic regions where major genes or QTL have been described earlier. In addition, new loci were also detected, providing opportunities to monitor genetic variation for crop improvement.     

Multifunction of autophagy-related genes in filamentous fungi

Autophagy (macroautophagy), a highly conserved eukaryotic mechanism, is a non-selective degradation process, helping to maintain a balance between the synthesis, degradation and subsequent recycling of macromolecules to overcome various stress conditions. The term autophagy denotes any cellular process which involves the delivery of cytoplasmic material to the lysosome for degradation. Autophagy, in filamentous fungi plays a critical role during cellular development and pathogenicity. Autophagy, like the mitogen-activated protein (MAP) kinase cascade and nutrient-sensing cyclic AMP (cAMP) pathway, is also an important process for appressorium turgor accumulation in order to penetrate the leaf surface of host plant and destroy the plant defense. Yeast, an autophagy model, has been used to compare the multi-valued functions of ATG (autophagy-related genes) in different filamentous fungi. The autophagy machinery in both yeast and filamentous fungi is controlled by Tor kinase and both contain two distinct phosphatidylinositol 3-kinase complexes. In this review, we focus on the functions of ATG genes during pathogenic development in filamentous fungi.     

Boron δ-doped (111) diamond solution gate field effect transistors

A solution gate field effect transistor (SGFET) using an oxidised boron δ-doped channel on (111) diamond is presented for the first time. Employing an optimised plasma chemical vapour deposition (PECVD) recipe to deposit δ-layers, SGFETs show improved current-voltage (I-V) characteristics in comparison to previous similar devices fabricated on (100) and polycrystalline diamond, where the device is shown to operate in the enhancement mode of operation, achieving channel pinch-off and drain-source current saturation within the electrochemical window of diamond. A maximum gain and transconductance of 3 and 200μS/mm are extracted, showing comparable figures of merit to hydrogen-based SGFET. The oxidised device shows a site-binding model pH sensitivity of 36 mV/pH, displaying fast temporal responses. Considering the biocompatibility of diamond towards cells, the device's highly mutable transistor characteristics, pH sensitivity and stability against anodic oxidation common to hydrogen terminated diamond SGFET, oxidised boron δ-doped diamond SGFETs show promise for the recording of action potentials from electrogenic cells.     

Pistagremic acid a new leishmanicidal triterpene isolated from Pistacia integerrima Stewart

The present study was designed to investigate the whole plant of Pistacia integerrima Stewart in order to examine the pharmacological basis of the use of the plant in folk medicine for the treatment of infectious diseases and disorder. Phytochemical and pharmacological studies led to the isolation of a new triterpene pistagremic acid (3-methyl-7-(4,4,10,13,14-pentamethyl-3-2,3,4,5,6,7,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-17-yl)-oct-3-enoic). Pistagremic acid showed significant leishmanicidal activity (IC(50): 6.71 ± 0.09 μM) against Leishmania major (DESTO) promastigotes in comparison to standard compound amphotericin B (IC(50): 0.21 ± 0.06 μM).     

Cysteine 195 Has a Critical Functional Role in Catalysis by Isocitrate Lyase from Escherichia coli

Cysteine 195 in isocitrate lyase from Escherichia coli has been replaced by directed mutagenesis. Substitution by Ser yields enzyme with a k_cat that is 0.03% that of wild type, and substitution by Ala, Gly, Thr, or Val yields completely inactive enzyme. The present results are consistent with a functional role of Cys 195. Received: 26 March 1997 / Accepted: 29 April 1997