The Scirtothrips dorsalis Species Complex: Endemism and Invasion in a Global Pest

Invasive arthropods pose unique management challenges in various environments, the first of which is correct identification. This apparently mundane task is particularly difficult if multiple species are morphologically indistinguishable but accurate identification can be determined with DNA barcoding provided an adequate reference set is available. Scirtothrips dorsalis is a highly polyphagous plant pest with a rapidly expanding global distribution and this species, as currently recognized, may be comprised of cryptic species. Here we report the development of a comprehensive DNA barcode library for S. dorsalis and seven nuclear markers via next-generation sequencing for identification use within the complex. We also report the delimitation of nine cryptic species and two morphologically distinguishable species comprising the S. dorsalis species complex using histogram analysis of DNA barcodes, Bayesian phylogenetics, and the multi-species coalescent. One member of the complex, here designated the South Asia 1 cryptic species, is highly invasive, polyphagous, and likely the species implicated in tospovirus transmission. Two other species, South Asia 2, and East Asia 1 are also highly polyphagous and appear to be at an earlier stage of global invasion. The remaining members of the complex are regionally endemic, varying in their pest status and degree of polyphagy. In addition to patterns of invasion and endemism, our results provide a framework both for identifying members of the complex based on their DNA barcode, and for future species delimiting efforts.     

Coupling scanning electron microscopy with DNA bar coding: a novel approach for thrips identification

The small size and cryptic nature of thrips pests often make their monitoring and the identification process difficult. With the aim to obtain accurate identification of various pest species in the order Thysanoptera, a pilot study was conducted on an invasive thrips species Scirtothrips dorsalis Hood in Florida. The specific objective of this pilot study was to assess if the thrips specimens processed to be observed under scanning electron microscopy (SEM) can be further utilized for DNA based assays. Larvae and adults of S. dorsalis were subjected to traditional morphological identification using high resolution SEM prior to their DNA extraction. Sequence results of both mtCO1 and ITS rDNA of individual larva and adult S. dorsalis were found to be in agreement with the taxonomic identification conducted using SEM and each result confirmed the other technique. Our results suggest that steps involved during specimen preparation and observation under SEM does not impact DNA analysis of the sample. The two techniques together could be used for the correct identification of various thrips species using the same specimen. The proof of concept was further tested on three other important thrips species Frankliniella occidentalis (Pergande), F. schultzei (Trybom) and Thrips palmi Karny, which confirmed the robustness of the technique. The technique has broader significance for different areas under entomological sciences especially medical, forensic and taxonomic studies where the samples put under a high beam of ions for investigation are often required for DNA analysis.     

CD44 expression is developmentally regulated in the mouse lens and increases in the lens epithelium after injury

Hyaluronan is an oligosaccharide found in the pericellular matrix of numerous cell types and hyaluronan-induced signaling is known to facilitate fibrosis and cancer progression in some tissues. Hyaluronan is also commonly instilled into the eye during cataract surgery to protect the corneal endothelium from damage. Despite this, little is known about the distribution of hyaluronan or its receptors in the normal ocular lens. In this study, hyaluronan was found throughout the mouse lens, with apparently higher concentrations in the lens epithelium. CD44, a major cellular receptor for hyaluronan, is expressed predominately in mouse secondary lens fiber cells born from late embryogenesis into adulthood. Surgical removal of lens fiber cells from adult mice resulted in a robust upregulation of CD44 protein, which preceded the upregulation of α-smooth muscle actin expression typically used as a marker of epithelial–mesenchyma transition in this model of lens epithelial cell fibrosis. Mice lacking the CD44 gene had morphologically normal lenses with a response to lens fiber cell removal similar to wildtype, although they exhibited an increase in cell-associated hyaluronan. Overall, these data suggest that lens cells have a hyaluronan-containing pericellular matrix whose structure is partially regulated by CD44. Further, these data indicate that CD44 upregulation in the lens epithelium may be an earlier marker of lens injury responses in the mouse lens than the upregulation of α-smooth muscle actin.     

A Cdc42 Activation Cycle Coordinated by PI 3-Kinase during Fc Receptor-mediated Phagocytosis

Fcγ Receptor (FcR)-mediated phagocytosis by macrophages requires phosphatidylinositol 3-kinase (PI3K) and activation of the Rho-family GTPases Cdc42 and Rac1. Cdc42 is activated at the advancing edge of the phagocytic cup, where actin is concentrated, and is deactivated at the base of the cup. The timing of 3′ phosphoinositide (3′PI) concentration changes in cup membranes suggests a role for 3′PIs in deactivation of Cdc42. This study examined the relationships between PI3K and the patterns of Rho-family GTPase signaling during phagosome formation. Inhibition of PI3K resulted in persistently active Cdc42 and Rac1, but not Rac2, in stalled phagocytic cups. Patterns of 3′PIs and Rho-family GTPase activities during phagocytosis of 5- and 2-μm-diameter microspheres indicated similar underlying mechanisms despite particle size–dependent sensitivities to PI3K inhibition. Expression of constitutively active Cdc42(G12V) increased 3′PI concentrations in plasma membranes and small phagosomes, indicating a role for Cdc42 in PI3K activation. Cdc42(G12V) inhibited phagocytosis at a later stage than inhibition by dominant negative Cdc42(N17). Together, these studies identified a Cdc42 activation cycle organized by PI3K, in which FcR-activated Cdc42 stimulates PI3K and actin polymerization, and the subsequent increase of 3′PIs in cup membranes inactivates Cdc42 to allow actin recycling necessary for phagosome formation.     

Study on the Variations of Mineral Elements in Swertia speciosa (G. Don)

Variations of micro- and macrominerals concentration in Swertia speciosa were determined by atomic absorption spectroscopy. The mineral elements showed significant changes in roots and leaves collected from different altitudes. Among all the elements, highest concentration (more than 2,000 mg/kg) of Ca and K were recorded in S. speciosa and the concentration of other elements analyzed in the study decreased in the order Fe>Na>Zn>Co>Li>Cu>Mn.     

Isolation and characterisation of EfeM, a periplasmic component of the putative EfeUOBM iron transporter of Pseudomonas syringae pv. syringae

The EfeM protein is a component of the putative EfeUOBM iron-transporter of Pseudomonas syringae pathovar syringae and is thought to act as a periplasmic, ferrous-iron binding protein. It contains a signal peptide of 34 amino acid residues and a C-terminal ‘Peptidase_M75’ domain of 251 residues. The C-terminal domain contains a highly conserved ‘HXXE’ motif thought to act as part of a divalent cation-binding site. In this work, the gene (efeM or ‘Psyr_3370’) encoding EfeM was cloned and over-expressed in Escherichia coli, and the mature protein was purified from the periplasm. Mass spectrometry confirmed the identity of the protein (M_W 27,772 Da). Circular dichroism spectroscopy of EfeM indicated a mainly α-helical structure, consistent with bioinformatic predictions. Purified EfeM was crystallised by hanging-drop vapor diffusion to give needle-shaped crystals that diffracted to a resolution of 1.6 Å. This is the first molecular study of a peptidase M75 domain with a presumed iron transport role.     

Observation and kinematic description of long actin tracks induced by spherical beads

We report an in vitro study comparing the growth of long actin tails induced by spherical beads coated with the verprolin central acidic domain of the polymerization enzyme N-WASP to that induced by Listeria monocytogenes in similar cellular extracts. The tracks behind the beads show characteristic differences in shape and curvature from those left by the bacteria, which have an elongated shape and a similar polymerization-inducing enzyme distributed only on the rear surface of the cell. The experimental tracks are simulated using a generalized kinematic model, which incorporates three modes of bead rotation with respect to the tail. The results show that the trajectories of spherical beads are mechanically deterministic rather than random, as suggested by stochastic models. Assessment of the bead rotation and its mechanistic basis offers insights into the biological function of actin-based motility.