Evolution and Diversity of a Fungal Self/Nonself Recognition Locus

Self/nonself discrimination is an essential feature for pathogen recognition and graft rejection and is a ubiquitous phenomenon in many organisms. Filamentous fungi, such as Neurospora crassa, provide a model for analyses of population genetics/evolution of self/nonself recognition loci due to their haploid nature, small genomes and excellent genetic/genomic resources. In N. crassa, nonself discrimination during vegetative growth is determined by 11 heterokaryon incompatibility (het) loci. Cell fusion between strains that differ in allelic specificity at any of these het loci triggers a rapid programmed cell death response.In this study, we evaluated the evolution, population genetics and selective mechanisms operating at a nonself recognition complex consisting of two closely linked loci, het-c (NCU03493) and pin-c (NCU03494). The genomic position of pin-c next to het-c is unique to Neurospora/Sordaria species, and originated by gene duplication after divergence from other species within the Sordariaceae. The het-c pin-c alleles in N. crassa are in severe linkage disequilibrium and consist of three haplotypes, het-c1/pin-c1, het-c2/pin-c2 and het-c3/pin-c3, which are equally frequent in population samples and exhibit trans-species polymorphisms. The absence of recombinant haplotypes is correlated with divergence of the het-c/pin-c intergenic sequence. Tests for positive and balancing selection at het-c and pin-c support the conclusion that both of these loci are under non-neutral balancing selection; other regions of both genes appear to be under positive selection. Our data show that the het-c2/pin-c2 haplotype emerged by a recombination event between the het-c1/pin-c1 and het-c3/pin-c3 approximately 3-12 million years ago.These results support models by which loci that confer nonself discrimination form by the association of polymorphic genes with genes containing HET domains. Distinct allele classes can emerge by recombination and positive selection and are subsequently maintained by balancing selection and divergence of intergenic sequence resulting in recombination blocks between haplotypes

Four advances in carbon-carbon materials technology

Carbon-carbon composites are a specialty class of materials having many unique properties making these composites attractive for a variety of demanding engineering applications. Chief among these properties are exceptional retention of mechanical properties at temperatures as high as 4000 F, excellent creep resistance, and low density (1.6 to 1.8 g/cu cm). Although carbon-carbon composites are currently in service in a variety of applications, much development work remains to be accomplished before these materials can be considered to be fully mature, realizing their full potential. Four recent technology advances holding particular promise for overcoming current barriers to the wide-spread commercialization of carbon-carbon composites are described. These advances are: markedly improved interlaminar strengths (more than doubled) of two dimensional composites achieved by whiskerization of the fabric reinforcing plies, simultaneously improved oxidation resistance and mechanical properties achieved by the incorporation of matrix-phase oxidation inhibitors based on carborane chemistry, improved oxidation resistance achieved by compositionally graded oxidation protective coatings, and markedly reduced processing times (hours as opposed to weeks or months) accomplished through a novel process of carbon infiltration and coatings deposition based on the use of liquid-phase precursor materials

Neurospora crassa transcriptomics reveals oxidative stress and plasma membrane homeostasis biology genes as key targets in response to chitosan

Chitosan is a natural polymer with antimicrobial activity. Chitosan causes plasma membrane permeabilization and induction of intracellular reactive oxygen species (ROS) in Neurospora crassa. We have determined the transcriptional profile of N. crassa to chitosan and identified the main gene targets involved in the cellular response to this compound. Global network analyses showed membrane, transport and oxidoreductase activity as key nodes affected by chitosan. Activation of oxidative metabolism indicates the importance of ROS and cell energy together with plasma membrane homeostasis in N. crassa response to chitosan. Deletion strain analysis of chitosan susceptibility pointed NCU03639 encoding a class 3 lipase, involved in plasma membrane repair by lipid replacement, and NCU04537 a MFS monosaccharide transporter related to assimilation of simple sugars, as main gene targets of chitosan. NCU10521, a glutathione S-transferase-4 involved in the generation of reducing power for scavenging intracellular ROS is also a determinant chitosan gene target. Ca2+ increased tolerance to chitosan in N. crassa. Growth of NCU10610 (fig 1 domain) and SYT1 (a synaptotagmin) deletion strains was significantly increased by Ca2+ in the presence of chitosan. Both genes play a determinant role in N. crassa membrane homeostasis. Our results are of paramount importance for developing chitosan as an antifungal.This work was supported by the National Institutes of Health (USA) grant GM060468 to NLG and Spanish Ministry of Economy and Competitiveness Grant AGL 2011-29297/AGR to LVLL

The regulatory and transcriptional landscape associated with carbon utilization in a filamentous fungus.

Filamentous fungi, such as Neurospora crassa, are very efficient in deconstructing plant biomass by the secretion of an arsenal of plant cell wall-degrading enzymes, by remodeling metabolism to accommodate production of secreted enzymes, and by enabling transport and intracellular utilization of plant biomass components. Although a number of enzymes and transcriptional regulators involved in plant biomass utilization have been identified, how filamentous fungi sense and integrate nutritional information encoded in the plant cell wall into a regulatory hierarchy for optimal utilization of complex carbon sources is not understood. Here, we performed transcriptional profiling of N. crassa on 40 different carbon sources, including plant biomass, to provide data on how fungi sense simple to complex carbohydrates. From these data, we identified regulatory factors in N. crassa and characterized one (PDR-2) associated with pectin utilization and one with pectin/hemicellulose utilization (ARA-1). Using in vitro DNA affinity purification sequencing (DAP-seq), we identified direct targets of transcription factors involved in regulating genes encoding plant cell wall-degrading enzymes. In particular, our data clarified the role of the transcription factor VIB-1 in the regulation of genes encoding plant cell wall-degrading enzymes and nutrient scavenging and revealed a major role of the carbon catabolite repressor CRE-1 in regulating the expression of major facilitator transporter genes. These data contribute to a more complete understanding of cross talk between transcription factors and their target genes, which are involved in regulating nutrient sensing and plant biomass utilization on a global level

Hermetic SiC-SiC composite tubes

SiC-SiC composites have good potential for structural applications but are limited by expensive forming techniques. A high purity {beta}-SiC fiber produced by MER, and a polymer derived SiC matrix were used to fabricate small diameter hermetic SiC-SiC tubes. The process was optimized to prevent the formation of a brittle structure while rapidly forming a dense matrix. This tube was made hermetic by first coating the surface of the tube with a silicon carbide particle filled polymer slurry, followed by a Chemical Vapor Infiltration/Deposition (CVI/CVD) SiC deposition which was performed to close any residual porosity on the composite tube surface. X-ray diffraction and Transmission Electron Microscopy (TEM) examination was performed to determine the fiber and matrix structures. These tubes were found to be impermeable to helium with leak rates below 10{sup {minus}9} cc/sec as determined by testing similar to MIL-STD-883D, method 1014.10. This high level of impermeability was sustained following thermal cycling between room temperature and 1,520 C

Kinetic viscoelasticity modeling applied to degradation during carbon–carbon composite processing

Kinetic viscoelasticity modeling has been successfully utilized to describe phenomena during cure of thermoset based carbon fiber reinforced matrices. The basic difference from classic viscoelasticity is that the fundamental material descriptors change as a result of reaction kinetics. Accordingly, we can apply the same concept for different kinetic phenomena with simultaneous curing and degradation. The application of this concept can easily be utilized in processing and manufacturing of carbon–carbon composites, where phenolic resin matrices are cured degraded and reinfused in a carbon fiber bed. This work provides a major step towards understanding complex viscoelastic phenomena that go beyond simple thermomechanical descriptors.United States. Air Force Office of Scientific ResearchNational Science Foundation (U.S.) (Joint U.S.-Greece Program

Genomic organization and complete sequence of the human gene encoding the β-subunit of the cGMP phosphodiesterase and its localisation to 4p16.3

As part of the search for the Huntington disease (HD) gene we have cloned and sequenced 34 kb of genomic DNA containing the full-length gene for the β-subunit of the human cGMP phosphodiesterase (β-cGMP PDE). This gene is localized to 4p16.3 about 700 kb proximal to the 4p telomere and represents the most telomeric gene characterized on 4p to date. We show that this gene is comprised of 22 exons spanning approximately 43 kb of genomic DNA. We also provide 400 bp immediately 5′ to the putative initiator methionine and 700 bp of 3′ flanking sequences. Northern blot analysis of several human tissues revealed a highly abundant 3.5 kb transcript and a minor signal of 4.5 kb in retinal tissue. Alignment of the deduced amino acid sequence to the previously identified β-subunits of the cGMP PDEs of mouse and cow demonstrates highly significant similarities and, therefore, confirms the identity of the cloned gene. A defect in the β-subunit of the cGMP PDE gene has been shown recently to be the cause for the retinal degeneration in the rd mouse. The cloning of the human homolog and the knowledge of its genomic organization with exon/intron boundaries will allow rapid assessment of the role of this gene in the causation of human retinopathies

‘GET LIT!’: EXAMINING LITERATURE SELECTION AND PROGRAMMATIC METHOD BASED ON THEMES OBSERVED BETWEEN TEACHER AND STUDENT PERSPECTIVE OF WHAT MAKES MERITORIOUS WIND BAND LITERATURE.

This study is qualitative in nature and explores the felt experiences of high school and university wind band educators and students from various demographic groups regarding their perspectives on what qualifies a piece of wind band literature as meritorious. The study included a survey, for both director and student participants, which examined the preferences of both directors and students and offered an opportunity to voice their opinion of what is quality wind band literature in their own words. Through the process of surveying high school and university wind band directors and students, four major themes emerged that directors in current practice and pre-professionals in training can apply to their wind band literature selection