Indigenous demosponge spicules in a Late Devonian stromatoporoid basal skeleton from the Frasnian of Belgium

This paper records the first example of a demosponge spicule framework in a single specimen of a Devonian stromatoporoid from the Frasnian of southern Belgium. The small sample (2.5 × 2 cm) is a component in a brecciated carbonate from a carbonate mound in La Boverie Quarry 30 km east of Dinant. Because of the small size of the sample, generic identification is not confirmed, but the stromatoporoid basal skeleton is similar to the genus Stromatopora. The spicules are arranged in the calcified skeleton, but not in the gallery space, and are recrystallized as multi-crystalline calcite. The spicules fall into two size ranges: 10-20 μm diameter and 500-2000 μm long for the large ones and between 5-15 μm diameter and 50-100 μm length for the small ones. In tangential section, the spicules are circular, they have a simple structure, and no axial canal has been preserved. The large spicules are always monaxons, straight or slightly curved styles or strongyles. The spicules most closely resemble halichondrid/axinellid demosponge spicules and are important rare evidence of the existence of spicules in Palaeozoic stromatoporoids, reinforcing the interpretation that stromatoporoids were sponges. The basal skeleton may have had an aragonitic spherulitic mineralogy. Furthermore, the spicules indicate that this stromatoporoid sample is a demosponge. © 2014 Lethaia Foundation. Published by John Wiley & Sons Ltd

EVALUATING THE USE OF SECOND LIFE\u3csup\u3eTM\u3c/sup\u3e FOR VIRTUAL TEAM-BASED LEARNING IN AN ONLINE UNDERGRADUATE ANATOMY COURSE

Team-based learning (TBL) is one strategy for improving team-work and critical thinking skills. It has proven to be an engaging teaching pedagogy in face-to-face classes, however, to our knowledge, has never been implemented online in a 3-D virtual world. We implemented virtual TBLs in an online undergraduate anatomy course using Second LifeTM, and evaluated whether it engaged students. This study was conducted over 2 semesters with 39 total students. Surveys and content analysis of transcripts were used to evaluate student engagement. Our results indicate virtual TBLs were engaging for most students. The average engagement score was 7.8 out of 10 with 89.2% of students reporting a score of 6 or above. Students exhibited high levels of cognitive engagement during the clinical application portion of the TBL process. Males felt more emotionally engaged than females, however, most measures of engagement indicated no differences between groups of students (mode of communication, previous technology experience, gender, and performance); therefore, virtual TBLs may be engaging for a broad range of students. 95% of students agreed that this was a worthwhile experience. In light of this evidence, we feel that virtual TBL sessions are valuable, and could be implemented in other online courses

Population Genomic Analysis Reveals Differential Evolutionary Histories and Patterns of Diversity across Subgenomes and Subpopulations of Brassica napus L.

The allotetraploid species Brassica napus L. is a global crop of major economic importance, providing canola oil (seed) and vegetables for human consumption and fodder and meal for livestock feed. Characterizing the genetic diversity present in the extant germplasm pool of B. napus is fundamental to better conserve, manage and utilize the genetic resources of this species. We used sequence-based genotyping to identify and genotype 30,881 SNPs in a diversity panel of 782 B. napus accessions, representing samples of winter and spring growth habits originating from 33 countries across Europe, Asia and America. We detected strong population structure broadly concordant with growth habit and geography, and identified three major genetic groups: spring (SP), winter Europe (WE), and winter Asia (WA). Subpopulation-specific polymorphism patterns suggest enriched genetic diversity within the WA group and a smaller effective breeding population for the SP group compared to WE. Interestingly, the two subgenomes of B. napus appear to have different geographic origins, with phylogenetic analysis placing WE and WA as basal clades for the other subpopulations in the C and A subgenomes, respectively. Finally, we identified 16 genomic regions where the patterns of diversity differed markedly from the genome-wide average, several of which are suggestive of genomic inversions. The results obtained in this study constitute a valuable resource for worldwide breeding efforts and the genetic dissection and prediction of complex B. napus traits

Field-based high-throughput plant phenotyping reveals the temporal patterns of quantitative trait loci associated with stress-responsive traits in cotton

The application of high-throughput plant phenotyping (HTPP) to continuously study plant populations under relevant growing conditions creates the possibility to more efficiently dissect the genetic basis of dynamic adaptive traits. Towards this end, we employed a field-based HTPP system that deployed sets of sensors to simultaneously measure canopy temperature, reflectance, and height on a cotton (Gossypium hirsutum L.) recombinant inbred line mapping population. The evaluation trials were conducted under well-watered and water-limited conditions in a replicated field experiment at a hot, arid location in central Arizona, with trait measurements taken at different times on multiple days across three years. Canopy temperature, normalized difference vegetation index (NDVI), height, and leaf area index (LAI) displayed moderate to high broad-sense heritabilities as well as varied interactions among genotypes with water regime and time of day. Distinct temporal patterns of quantitative trait loci (QTL) expression were mostly observed for the more dynamic HTPP canopy traits, canopy temperature and NDVI, and varied across plant developmental stages. In addition, the strength of correlation between HTPP canopy and agronomic traits such as lint yield displayed a time-dependent relationship. We also found that the position of some QTL controlling HTPP canopy traits were shared with agronomic and physiological traits. This work demonstrates the novel use of a field-based, HTPP system to study the genetic basis of stress-adaptive traits in cotton, and these results have the potential to facilitate the development of stress-resilient cotton cultivars

Fitness costs of key point mutations that underlie acaricide target-site resistance in the two-spotted spider mite Tetranychus urticae

The frequency of insecticide/acaricide target-site resistance is increasing in arthropod pest populations and is typically underpinned by single point mutations that affect the binding strength between the insecticide/acaricide and its target-site. Theory predicts that although resistance mutations clearly have advantageous effects under the selection pressure of the insecticide/acaricide, they might convey negative pleiotropic effects on other aspects of fitness. If such fitness costs are in place, target-site resistance is thus likely to disappear in the absence of insecticide/acaricide treatment, a process that would counteract the spread of resistance in agricultural crops. Hence, there is a great need to reliably quantify the various potential pleiotropic effects of target-site resistance point mutations on arthropod fitness. Here, we used near-isogenic lines of the spider mite pest Tetranychus urticae that carry well-characterized acaricide target-site resistance mutations to quantify potential fitness costs. Specifically, we analyzed P262T in the mitochondrial cytochrome b, the combined G314D and G326E substitutions in the glutamate-gated chloride channels, L1024V in the voltage-gated sodium channel, and I1017F in chitin synthase 1. Five fertility life table parameters and nine single-generation life-history traits were quantified and compared across a total of 15 mite lines. In addition, we monitored the temporal resistance level dynamics of populations with different starting frequency levels of the chitin synthase resistant allele to further support our findings. Three target-site resistance mutations, I1017F and the co-occurring G314D and G326E mutations, were shown to significantly and consistently alter certain fitness parameters in T. urticae. The other two mutations (P262T and L1024V) did not result in any consistent change in a fitness parameter analyzed in our study. Our findings are discussed in the context of the global spread of T. urticae pesticide resistance and integrated pest management

Extensive Copy-Number Variation of Young Genes across Stickleback Populations

MM received funding from the Max Planck innovation funds for this project. PGDF was supported by a Marie Curie European Reintegration Grant (proposal nr 270891). CE was supported by German Science Foundation grants (DFG, EI 841/4-1 and EI 841/6-1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Patterns and rates of intron divergence between humans and chimpanzees

BACKGROUND: Introns, which constitute the largest fraction of eukaryotic genes and which had been considered to be neutral sequences, are increasingly acknowledged as having important functions. Several studies have investigated levels of evolutionary constraint along introns and across classes of introns of different length and location within genes. However, thus far these studies have yielded contradictory results. RESULTS: We present the first analysis of human-chimpanzee intron divergence, in which differences in the number of substitutions per intronic site (K(i)) can be interpreted as the footprint of different intensities and directions of the pressures of natural selection. Our main findings are as follows: there was a strong positive correlation between intron length and divergence; there was a strong negative correlation between intron length and GC content; and divergence rates vary along introns and depending on their ordinal position within genes (for instance, first introns are more GC rich, longer and more divergent, and divergence is lower at the 3' and 5' ends of all types of introns). CONCLUSION: We show that the higher divergence of first introns is related to their larger size. Also, the lower divergence of short introns suggests that they may harbor a relatively greater proportion of regulatory elements than long introns. Moreover, our results are consistent with the presence of functionally relevant sequences near the 5' and 3' ends of introns. Finally, our findings suggest that other parts of introns may also be under selective constraints

The evolution of metazoan extracellular matrix

The modular domain structure of extracellular matrix (ECM) proteins and their genes has allowed extensive exon/domain shuffling during evolution to generate hundreds of ECM proteins. Many of these arose early during metazoan evolution and have been highly conserved ever since. Others have undergone duplication and divergence during evolution, and novel combinations of domains have evolved to generate new ECM proteins, particularly in the vertebrate lineage. The recent sequencing of several genomes has revealed many details of this conservation and evolution of ECM proteins to serve diverse functions in metazoa.Howard Hughes Medical Institut

WNT/β-Catenin Signalling and Epithelial Patterning in the Homoscleromorph Sponge Oscarella

Sponges branch basally in the metazoan phylogenetic tree and are thus well positioned to provide insights into the evolution of mechanisms controlling animal development, likely to remain active in adult sponges. Of the four sponge clades, the Homoscleromorpha are of particular interest as they alone show the “true” epithelial organization seen in other metazoan phyla (the Eumetazoa). We have examined the deployment in sponges of Wnt signalling pathway components, since this pathway is an important regulator of many developmental patterning processes. We identified a reduced repertoire of three divergent Wnt ligand genes in the recently-sequenced Amphimedon queenslandica (demosponge) genome and two Wnts from our EST collection from the homoscleromorph Oscarella lobularis, along with well-conserved genes for intracellular pathway components (β-catenin, GSK3β). Remarkably, the two O. lobularis Wnt genes showed complementary expression patterns in relation to the evenly spaced ostia (canal openings) of the exopinacoderm (ectoderm), highly reminiscent of Wnt expression during skin appendage formation in vertebrates. Furthermore, experimental activation of the Wnt/β-catenin pathway using GSK3β inhibitors provoked formation of ectopic ostia, as has been shown for epithelial appendages in Eumetazoa. We thus suggest that deployment of Wnt signalling is a common and perhaps ancient feature of metazoan epithelial patterning and morphogenesis