From genes to geography: a genetic similarity rule for arthropod community structure at multiple geographic scales

We tested the hypothesis that leaf modifying arthropod communities are correlated with cottonwood host plant genetic variation from local to regional scales. Although recent studies found that host plant genetic composition can structure local dependent herbivore communities, the abiotic environment is a stronger factor than the genetic effect at increasingly larger spatial scales. In contrast to these studies we found that dependent arthropod community structure is correlated with both the cross type composition of cottonwoods and individual genotypes within local rivers up to the regional scale of 720,000 km(2) (Four Corner States region in the southwestern USA). Across this geographical extent comprising two naturally hybridizing cottonwood systems, the arthropod community follows a simple genetic similarity rule: genetically similar trees support more similar arthropod communities than trees that are genetically dissimilar. This relationship can be quantified with or without genetic data in Populus.     

The phylogenetic potential of entire 26S rDNA sequences in plants

18S ribosomal RNA genes are the most widely used nuclear sequences for phylogeny reconstruction at higher taxonomic levels in plants. However, due to a conservative rate of evolution, 18S rDNA alone sometimes provides too few phylogenetically informative characters to resolve relationships adequately. Previous studies using partial sequences have suggested the potential of 26S or large-subunit (LSU) rDNA for phylogeny retrieval at taxonomic levels comparable to those investigated with 18S rDNA. Here we explore the patterns of molecular evolution of entire 26S rDNA sequences and their impact on phylogeny retrieval. We present a protocol for PCR amplification and sequencing of entire (approximately 3.4 kb) 26S rDNA sequences as single amplicons, as well as primers that can be used for amplification and sequencing. These primers proved useful in angiosperms and Gnetales and likely have broader applicability. With these protocols and primers, entire 26S rDNA sequences were generated for a diverse array of 15 seed plants, including basal eudicots, monocots, and higher eudicots, plus two representatives of Gnetales. Comparisons of sequence dissimilarity indicate that expansion segments (or divergence domains) evolve 6.4 to 10.2 times as fast as conserved core regions of 26S rDNA sequences in plants. Additional comparisons indicate that 26S rDNA evolves 1.6 to 2.2 times as fast as and provides 3.3 times as many phylogenetically informative characters as 18S rDNA; compared to the chloroplast gene rbcL, 26S rDNA evolves at 0.44 to 1.0 times its rate and provides 2.0 times as many phylogenetically informative characters. Expansion segment sequences analyzed here evolve 1.2 to 3.0 times faster than rbcL, providing 1.5 times the number of informative characters. Plant expansion segments have a pattern of evolution distinct from that found in animals, exhibiting less cryptic sequence simplicity, a lower frequency of insertion and deletion, and greater phylogenetic potential.      

Human whole body imaging and detection of breast tumours by n.m.r

A brief review of recent developments in line scan imaging of large objects is given, together with some representative images showing anatomical detail and a discussion of some spin-lattice relaxation time mapping results. Current progress in high speed imaging by means of the echo planar technique is reported and some preliminary results obtained at both 15.0 and 4.0 MHz are discussed.     

Plant genetics predicts intra-annual variation in phytochemistry and arthropod community structure

With the emerging field of community genetics, it is important to quantify the key mechanisms that link genetics and community structure. We studied cottonwoods in common gardens and in natural stands and examined the potential for plant chemistry to be a primary mechanism linking plant genetics and arthropod communities. If plant chemistry drives the relationship between plant genetics and arthropod community structure, then several predictions followed. We would find (i) the strongest correlation between plant genetic composition and chemical composition; (ii) an intermediate correlation between plant chemical composition and arthropod community composition; and (iii) the weakest relationship between plant genetic composition and arthropod community composition. Our results supported our first prediction: plant genetics and chemistry had the strongest correlation in the common garden and the wild. Our results largely supported our second prediction, but varied across space, seasonally, and according to arthropod feeding group. Plant chemistry played a larger role in structuring common garden arthropod communities relative to wild communities, free-living arthropods relative to leaf and stem modifiers, and early-season relative to late-season arthropods. Our results did not support our last prediction, as host plant genetics was at least as tightly linked to arthropod community structure as plant chemistry, if not more so. Our results demonstrate the consistency of the relationship between plant genetics and biodiversity. Additionally, plant chemistry can be an important mechanism by which plant genetics affects arthropod community composition, but other genetic-based factors are likely involved that remain to be measured.     

Murine Borrelia arthritis is highly dependent on ASC and caspase-1, but independent of NLRP3

Introduction

The protein platform called the NOD-like-receptor -family member (NLRP)-3 inflammasome needs to be activated to process intracellular caspase-1. Active caspase-1 is able to cleave pro-Interleukin (IL)-1β, resulting in bioactive IL-1β. IL-1β is a potent proinflammatory cytokine, and thought to play a key role in the pathogenesis of Lyme arthritis, a common manifestation of Borrelia burgdorferi infection. The precise pathways through which B. burgdorferi recognition leads to inflammasome activation and processing of IL-1β in Lyme arthritis has not been elucidated. In the present study, we investigated the contribution of several pattern recognition receptors and inflammasome components in a novel murine model of Lyme arthritis.

Methods

Lyme arthritis was elicited by live B. burgdorferi, injected intra-articularly in knee joints of mice. To identify the relevant pathway components, the model was applied to wild-type, NLRP3-/-, ASC-/-, caspase-1-/-, NOD1-/-, NOD2-/-, and RICK-/- mice. As a control, TLR2-/-, Myd88-/- and IL-1R-/- mice were used. Peritoneal macrophages and bone marrow-derived macrophages were used for in vitro cytokine production and inflammasome activation studies. Joint inflammation was analyzed in synovial specimens and whole knee joints. Mann-Whitney U tests were used to detect statistical differences.

Results

We demonstrate that ASC/caspase-1-driven IL-1β is crucial for induction of B. burgdorferi-induced murine Lyme arthritis. In addition, we show that B. burgdorferi-induced murine Lyme arthritis is less dependent on NOD1/NOD2/RICK pathways while the TLR2-MyD88 pathway is crucial.

Conclusions

Murine Lyme arthritis is strongly dependent on IL-1 production, and B. burgdorferi induces inflammasome-mediated caspase-1 activation. Next to that, murine Lyme arthritis is ASC- and caspase-1-dependent, but NLRP3, NOD1, NOD2, and RICK independent. Also, caspase-1 activation by B. burgdorferi is dependent on TLR2 and MyD88. Based on present results indicating that IL-1 is one of the major mediators in Lyme arthritis, there is a rationale to propose that neutralizing IL-1 activity may also have beneficial effects in chronic Lyme arthritis.     

Tuning the Cellular Trafficking of the Lysosomal Peptide Transporter TAPL by its N‐terminal Domain

The homodimeric ATP‐binding cassette (ABC) transport complex TAPL (transporter associated with antigen processing‐like, ABCB9) translocates a broad spectrum of peptides from the cytosol into the lumen of lysosomes. The presence of an extra N‐terminal transmembrane domain (TMD0) lacking any sequence homology to known proteins distinguishes TAPL from most other ABC transporters of its subfamily. By dissecting TAPL, we could assign distinct functions to the core complex and TMD0. The core‐TAPL complex, composed of six predicted transmembrane helices and a nucleotide‐binding domain, is sufficient for peptide transport, showing that the core transport complex is correctly targeted to and assembled in the membrane. Strikingly, in contrast to the full‐length transporter, the core translocation complex is targeted preferentially to the plasma membrane. However, TMD0 alone, comprising a putative four transmembrane helix bundle, traffics to lysosomes. Upon coexpression, TMD0 forms a stable non‐covalently linked complex with the core translocation machinery and guides core‐TAPL into lysosomal compartments. Therefore, TMD0 represents a unique domain, which folds independently and encodes the information for lysosomal targeting. These outcomes are discussed in respect of trafficking, folding and function of TAPL.     

Native and exotic plants of fragments of sagebrush steppe produced by geomorphic processes versus land use

Habitat fragmentation and invasion by exotic species are regarded as major threats to the biodiversity of many ecosystems. We surveyed the plant communities of two types of remnant sagebrush-steppe fragments from nearby areas on the Snake River Plain of southeastern Idaho, USA. One type resulted from land use (conversion to dryland agriculture; hereafter AG Islands) and the other from geomorphic processes (Holocene volcanism; hereafter kipukas). We assessed two predictions for the variation in native plant species richness of these fragments, using structural equation models (SEM). First, we predicted that the species richness of native plants would follow the MacArthur–Wilson (M–W) hypothesis of island biogeography, as often is expected for the communities of habitat fragments. Second, we predicted a negative relationship between native and exotic plants, as would be expected if exotic plants are decreasing the diversity of native plants. Finally, we assessed whether exotic species were more strongly associated with the fragments embedded in the agricultural landscape, as would be expected if agriculture had facilitated the introduction and naturalization of non-native species, and whether the communities of the two types of fragments were distinct. Species richness of native plants was not strongly correlated with M–W characteristics for either the AG Islands or the **kipukas. The AG Islands had more species and higher cover of exotics than the kipukas, and exotic plants were good predictors of native plant species richness. Our results support the hypothesis that proximity to agriculture can increase the diversity and abundance of exotic plants in native habitat. In combination with other information, the results also suggest that agriculture and exotic species have caused loss of native diversity and reorganization of the sagebrush-steppe plant community.     

Unique arthropod communities on different host-plant genotypes results in greater arthropod diversity

Studies on the effect of plant-species diversity on various ecological processes has led to the study of the effects of plant-genetic diversity in the context of community genetics. Arthropod diversity can increase with plant-species or plant-genetic diversity (Wimp et al. in Ecol Lett 7:776–780, 2004). Plant diversity effects can be difficult to separate from other ecological processes, for example, complementarity. We asked three basic questions: (1) Are arthropod communities unique on different host-plant genotypes? (2) Is arthropod diversity greater when associated with greater plant-genetic diversity? (3) Are arthropod communities more closely associated with host-plant genetics than the plant neighborhood? We studied canopy arthropods on Populus fremontii trees randomly planted in a common garden. All trees were planted in a homogeneous matrix, which helped to reduce P. fremontii neighborhood effects. One sample was comprised of few P. fremontii genotypes with many clones. A second sample was comprised of many P. fremontii genotypes with few clones. A second data set was used to examine the relationships between the arthropod community with P. fremontii genetic composition and the neighborhood composition of the focal host plant. Unique arthropod communities were associated with different P. fremontii genotypes, and arthropod community diversity was greater in the sample with greater P. fremontii genotypic diversity. Arthropod community similarity was negatively correlated with P. fremontii genetic distance, but arthropod community similarity was not related to the neighborhood of the P. fremontii host plant.