In earlier studies, the assimilation of selenate by plants appeared to be limited by its reduction, a step that is thought to be mediated by ATP sulfurylase. Here, the Arabidopsis APS1 gene, encoding a plastidic ATP sulfurylase, was constitutively overexpressed in Indian mustard (Brassica juncea). Compared with that in untransformed plants, the ATP sulfurylase activity was 2-to 2.5-fold higher in shoots and roots of transgenic seedlings, and 1.5-to 2-fold higher in shoots but not roots of selenate-supplied mature ATP-sulfurylaseoverexpressing (APS) plants. The APS plants showed increased selenate reduction: x-ray absorption spectroscopy showed that root and shoot tissues of mature APS plants contained mostly organic Se (possibly selenomethionine), whereas wild-type plants accumulated selenate. The APS plants were not able to reduce selenate when shoots were removed immediately before selenate was supplied. In addition, Se accumulation in APS plants was 2-to 3-fold higher in shoots and 1.5-fold higher in roots compared with wild-type plants, and Se tolerance was higher in both seedlings and mature APS plants. These studies show that ATP sulfurylase not only mediates selenate reduction in plants, but is also rate limiting for selenate uptake and assimilation.

Interest is increasing in using wetland plants in constructed wetlands to remove toxic elements from polluted wastewater. To identify those wetland plants that hyperaccumulate trace elements, 12 plant species were tested for their efficiency to bioconcentrate 10 potentially toxic trace elements including As, B, Cd, Cr, Cu, Pb, Mn, Hg, Ni, and Se. Individual plants were grown under carefully controlled conditions and supplied with 1 mg L−1 of each trace element individually for 10 d. Except B, all elements accumulated to much higher concentrations in roots than in shoots. Highest shoot tissue concentrations (mg kg−1 DW) of the various trace elements were attained by the following species: umbrella plant (Cyperus alternifolius L.) for Mn (198) and Cr (44); water zinnia (Wedelia trilobata Hitchc.) for Cd (148) and Ni (80); smartweed (Polygonum hydropiperoides Michx.) for Cu (95) and Pb (64); water lettuce (Pistia stratiotes L.) for Hg (92), As (34), and Se (39); and mare's tail (Hippuris vulgaris L.) for B (1132). Whereas, the following species attained the highest root tissue concentrations (mg kg−1 DW): stripped rush (Baumia rubiginosa) for Mn (1683); parrot's feather (Myriophyllum brasiliense Camb.) for Cd (1426) and Ni (1077); water lettuce for Cu (1038), Hg (1217), and As (177); smartweed for Cr (2980) and Pb (1882); mare's tail B (1277); and monkey flower (Mimulus guttatus Fisch.) for Se (384). From a phytoremediation perspective, smartweed was probably the best plant species for trace element removal from wastewater due to its faster growth and higher plant density.

Water is the natural medium of molecules in the cell and plays an important role in protein structure, function and interaction with small molecule ligands. However, the widely used molecular mechanics Poisson-Boltzmann surface area (MM/PBSA) method for binding energy calculation does not explicitly take account of water molecules that mediate key protein-ligand interactions. We have developed a protocol to include water molecules that mediate ligand-protein interactions as part of the protein structure in calculation of MM/PBSA binding energies (a method we refer to as water-MM/PBSA) for a series of JNK3 kinase inhibitors. Improved correlation between water-MM/PBSA binding energies and experimental IC50 values was obtained compared to that obtained from classical MM/PBSA binding energy. This improved correlation was further validated using sets of neuraminidase and avidin inhibitors. The observed improvement, however, appears to be limited to systems in which there are water-mediated ligand-protein hydrogen bond interactions. We conclude that the water-MM/PBSA method performs better than classical MM/PBSA in predicting binding affinities when water molecules play a direct role in mediating ligand-protein hydrogen bond interactions.

Background: Rheumatoid arthritis (RA) is an autoimmune disease that may be associated with gut microbiota via the aryl hydrocarbon receptor (AhR). Human umbilical mesenchymal stem cells (HUMSCs) have therapeutic potential against RA, but the underlying mechanism has not been fully elucidated. The purpose of this study was to explore the mechanism of action of HUMSCs in rats with collagen-induced arthritis (CIA). Method: HUMSCs (1 × 10 6) were transplanted into each rat with CIA. The tissue localization of HUMSCs and the therapeutic effects in the ankles were assessed. The immune status and expression of immune-related genes and proteins in related lymphoid tissues were subsequently tested. Furthermore, the levels of immune-related factors in serum and the changes in gut microbiota in the ileum were detected, and the levels of indole and their derivatives in plasma and the levels of AhR in the ileum were evaluated. Results: HUMSCs homed to the popliteal lymph node (PLN), mesenteric lymph node (MLN), ankle cartilage, and ileum mucosa in rats with CIA. The transplantation of HUMSCs reduced the pathology scores and the degree of bone damage in the ankles. The immune status of T regulatory cells (Tregs) and T helper (Th)17 cells and the gene expression levels of interleukin (IL)-10, transforming growth factor (TGF)-β1, and IL-17A were altered in the PLN, which is the lymph tissue closest to the nidus, and the MLN, which is one of the gut-associated lymphoid tissues (GALTs). The proportion and function of B cells, Tregs, and Th17 cells were regulated in other GALTs, namely,