Ecological and evolutionary implications of dinosaur feeding behaviour

Dinosaurs had a wide variety of feeding mechanisms that strongly impacted on their ecology and evolution. Here, we show how novel application of technologies borrowed from medicine and engineering, such as CT scanning and Finite Element Analysis, have recently been combined with traditional approaches to result in significant advances in our understanding of dinosaur palaeobiology. Taxon-specific studies are providing quantitative data that can be used to generate and test functional hypotheses relating to jaw mechanics and feeding behaviour. In turn, these data form a basis for investigating larger scale patterns of ecological and macroevolutionary change, such as possible coevolutionary interactions and the influence of feeding adaptations on species richness, which are of more general interest to ecologists and evolutionary biologists.     

Protein profiling of epidermal bladder cells from the halophyte Mesembryanthemum crystallinum

Plant epidermal trichomes are as varied in morphology as they are in function. In the halophyte Mesembryanthemum crystallinum, specialized trichomes called epidermal bladder cells (EBC) line the surface of leaves and stems, and increase dramatically in size and volume upon plant salt-treatment. These cells have been proposed to have roles in plant defense and UV protection, but primarily in sodium sequestration and as water reservoirs. To gain further understanding into the roles of EBC, a cell-type-specific proteomics approach was taken in which precision single-cell sampling of cell sap from individual EBC was combined with shotgun peptide sequencing (LC-MS/MS). Identified proteins showed diverse biological functions and cellular locations, with a high representation of proteins involved in H(+) -transport, carbohydrate metabolism, and photosynthesis. The proteome of EBC provides insight into the roles of these cells in ion and water homeostasis and raises the possibility that they are photosynthetically active and functioning in Crassulacean acid metabolism.     

Mannose Binding Lectin Is Required for Alphavirus-Induced Arthritis/Myositis

Mosquito-borne alphaviruses such as chikungunya virus and Ross River virus (RRV) are emerging pathogens capable of causing large-scale epidemics of virus-induced arthritis and myositis. The pathology of RRV-induced disease in both humans and mice is associated with induction of the host inflammatory response within the muscle and joints, and prior studies have demonstrated that the host complement system contributes to development of disease. In this study, we have used a mouse model of RRV-induced disease to identify and characterize which complement activation pathways mediate disease progression after infection, and we have identified the mannose binding lectin (MBL) pathway, but not the classical or alternative complement activation pathways, as essential for development of RRV-induced disease. MBL deposition was enhanced in RRV infected muscle tissue from wild type mice and RRV infected MBL deficient mice exhibited reduced disease, tissue damage, and complement deposition compared to wild-type mice. In contrast, mice deficient for key components of the classical or alternative complement activation pathways still developed severe RRV-induced disease. Further characterization of MBL deficient mice demonstrated that similar to C3^−/− mice, viral replication and inflammatory cell recruitment were equivalent to wild type animals, suggesting that RRV-mediated induction of complement dependent immune pathology is largely MBL dependent. Consistent with these findings, human patients diagnosed with RRV disease had elevated serum MBL levels compared to healthy controls, and MBL levels in the serum and synovial fluid correlated with severity of disease. These findings demonstrate a role for MBL in promoting RRV-induced disease in both mice and humans and suggest that the MBL pathway of complement activation may be an effective target for therapeutic intervention for humans suffering from RRV-induced arthritis and myositis.     

Testing microstructural adaptation in the earliest dental tools

Conodont elements are the earliest vertebrate dental structures. The dental tools on elements responsible for food fracture—cusps and denticles—are usually composed of lamellar crown tissue (a putative enamel homologue) and the enigmatic tissue known as ‘white matter’. White matter is unique to conodonts and has been hypothesized to be a functional adaptation for the use of elements as teeth. We test this quantitatively using finite-element analysis. Our results indicate that white matter allowed cusps and denticles to withstand greater tensile stresses than do cusps comprised solely of lamellar crown tissue. Microstructural variation is demonstrably associated with dietary and loading differences in teeth, so secondary loss of white matter through conodont phylogeny may reflect changes in diet and element occlusal kinematics. The presence, development and distribution of white matter could thus provide constraints on function in the first vertebrate dental structures.     

In vitro mutagenesis of Bacillus subtilis by using a modified Tn7 transposon with an outward-facing inducible promoter

A Tn7 donor plasmid, pTn7SX, was constructed for use with the model gram-positive bacterium Bacillus subtilis. This new mini-Tn7, mTn7SX, contains a spectinomycin resistance cassette and an outward-facing, xylose-inducible promoter, thereby allowing for the regulated expression of genes downstream of the transposon. We demonstrate that mTn7SX inserts are obtained at a high frequency and occur randomly throughout the B. subtilis genome. The utility of this system was demonstrated by the selection of mutants with increased resistance to the antibiotic fosfomycin or duramycin.     

Assessment of transgenic maize events produced by particle bombardment or Agrobacterium-mediated transformation

Particle bombardment and Agrobacterium-mediated transformation are two popular methods currently used for producing transgenic maize. Agrobacterium-mediated transformation is expected to produce transformants carrying fewer copies of the transgene and a more predictable pattern of integration. These putative advantages, however, tradeoff with transformation efficiency in maize when a standard binary vector transformation system is used. Using Southern, northern, real-time PCR, and real-time RT-PCR techniques, we compared transgene copy numbers and RNA expression levels in R₁ and R₂ generations of transgenic maize events generated using the above two gene delivery methods. Our results demonstrated that the Agrobacterium-derived maize transformants have lower transgene copies, and higher and more stable gene expression than their bombardment-derived counterparts. In addition, we showed that more than 70% of transgenic events produced from Agrobacterium-mediated transformation contained various lengths of the bacterial plasmid backbone DNA sequence, indicating that the Agrobacterium-mediated transformation was not as precise as previously perceived, using the current binary vector system.