Edaphic and Climatic Regulation of Microbial Carbon-Use Efficiency in Managed Semi-Arid Systems

In agricultural systems, an increasingly prevalent goal is to promote carbon sequestration into stable, mineral-associated soil organic matter, as increases in soil organic matter have been linked to increases in soil water-holding capacity and increases in nutrient availability. Because microbially-produced compounds are the foundation of soil organic matter, understanding interactions between management strategies and abiotic controls on microbial activity can prove invaluable for producers and ranchers interested in building soil organic matter and safeguarding production systems under a changing climate. The ability of microorganisms to contribute to growing soil organic matter stocks is dictated by their carbon-use efficiency, which is the proportion of carbon incorporated into their biomass relative to the total carbon they consume. In effect, higher values of microbial carbon-use efficiency reflect an increased potential for building microbially-derived soil organic matter. In an effort to better understand controls on microbial physiology and its role in soil organic matter formation, irrigation, plant functional type, and fertilization effects on carbon-use efficiency were evaluated in a water-limited system over the course of growing season. Results from our experiments indicated that moisture played a fundamental role in regulating microbial carbon-use efficiency, with low moistures decreasing carbon-use efficiency and thus decreasing the potential for soil organic matter formation. Conversely, other management strategies (e.g., plant functional type and fertilization) exerted little control on microbial carbon-use efficiency, especially when soil moisture was exceedingly low. Even with irrigation to supplement low moisture conditions during a growing season, microbial carbon-use efficiency still declined, likely resulting from increased water deficits as precipitation declined and evapotranspiration increased as the growing season progressed. Results from our experiments indicate that carbon-use efficiency may be intrinsically low in semi-arid systems compared to other systems without water limitations. By consequence, building soil organic matter stocks that can buffer the effects of climate change and improve water and nutrient retention may be difficult in semi-arid systems despite management techniques intended to promote soil organic matter formation

Learning with Diagrams: Effects on Inferences and the Integration of Information

Abstract. Students studied materials about the human heart and circulatory system using either (a) text only, (b) text with simple diagrams, or (c) text with detailed diagrams. During learning, students self-explained [1] the materials. Explanations were transcribed, separated into propositions, and analyzed according to the type of learning process they represented. Results demonstrated that diagrams promoted inference generation but did not affect other learning processes (such as elaboration or comprehension monitoring). However, only simple diagrams promoted generation of inferences that integrated domain information. Results indicate that diagrams may be useful because they guide the learner to engage in the cognitive processes required for deep understanding

Species Discrimination, Population Structure and Linkage Disequilibrium in Eucalyptus camaldulensis and Eucalyptus tereticornis Using SSR Markers

Eucalyptus camaldulensis and E. tereticornis are closely related species commonly cultivated for pulp wood in many tropical countries including India. Understanding the genetic structure and linkage disequilibrium (LD) existing in these species is essential for the improvement of industrially important traits. Our goal was to evaluate the use of simple sequence repeat (SSR) loci for species discrimination, population structure and LD analysis in these species. Investigations were carried out with the most common alleles in 93 accessions belonging to these two species using 62 SSR markers through cross amplification. The polymorphic information content (PIC) ranged from 0.44 to 0.93 and 0.36 to 0.93 in E. camaldulensis and E. tereticornis respectively. A clear delineation between the two species was evident based on the analysis of population structure and species-specific alleles. Significant genotypic LD was found in E. camaldulensis, wherein out of 135 significant pairs, 17 pairs showed r2≥0.1. Similarly, in E. tereticornis, out of 136 significant pairs, 18 pairs showed r2≥0.1. The extent of LD decayed rapidly showing the significance of association analyses in eucalypts with higher resolution markers. The availability of whole genome sequence for E. grandis and the synteny and co-linearity in the genome of eucalypts, will allow genome-wide genotyping using microsatellites or single nucleotide polymorphims

International genome-wide meta-analysis identifies new primary biliary cirrhosis risk loci and targetable pathogenic pathways.

Primary biliary cirrhosis (PBC) is a classical autoimmune liver disease for which effective immunomodulatory therapy is lacking. Here we perform meta-analyses of discovery data sets from genome-wide association studies of European subjects (n=2,764 cases and 10,475 controls) followed by validation genotyping in an independent cohort (n=3,716 cases and 4,261 controls). We discover and validate six previously unknown risk loci for PBC (Pcombined<5 × 10(-8)) and used pathway analysis to identify JAK-STAT/IL12/IL27 signalling and cytokine-cytokine pathways, for which relevant therapies exist

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Biological Response to Sulfate Salinity in Richland County, North Dakota

Soil salinization is a major threat to agricultural ecosystems. Consequently, an understanding of agro-ecosystem functions affected by increasing levels of soil salinity is critical for land management. The purpose of this research was to determine the effects of soil salinity on corn and soybean growth and soil microbial activity in southeastern North Dakota soils with naturally occurring soil salinity. A field study assessed corn and soybean yield, and a laboratory study assessed microbial respiration in response to increasing salinization. Both corn and soybean yield were significantly impacted by salinity in sandy loam soils, declining after a threshold of 4.57 dS m-1 and 2.98 dS m-1, respectively. These thresholds are higher and lower than previously established threshold tolerances for corn and soybean, respectively. Microbial respiration in sandy loam soils could not be significantly explained by ECe, potentially indicating a community composition that has acclimated to sulfate-based salinity in these soils