Solution structure of the Kaposi's sarcoma-associated herpesvirus K3 N-terminal domain reveals a Novel E2-binding C4HC3-type RING domain

RING domains are found in a large number of eukaryotic proteins. Most function as E3 ubiquitin-protein ligases, catalyzing the terminal step in the ubiquitination process. Structurally, these domains have been characterized as binding two zinc ions in a stable cross-brace motif. The tumorigenic human gamma-herpesvirus Kaposi's sarcoma-associated herpesvirus encodes a ubiquitin-protein ligase termed K3, which functions as an immune evasion molecule by ubiquitinating major histocompatibility complex class I. K3 possesses at its N terminus a domain related to cellular RING domains but with an altered zinc ligand arrangement. This domain was initially characterized as a plant homeodomain, a structure not previously known to function as an E3. Here, it is conclusively demonstrated that the K3 N-terminal domain is a variant member of the RING domain family and not a plant homeodomain. The domain is found to interact with the cellular ubiquitin-conjugating enzymes UbcH5A to -C and UbcH13, which dock to the equivalent surface as on classical cellular RING domains. Interaction with UbcH13 suggests a possible role for K3 in catalyzing Lys(63)-linked ubiquitination.     

Long-distance signals regulating stomatal conductance and leaf growth in tomato (Lycopersicon esculentum) plants subjected to partial root-zone drying

Tomato (Lycopersicon esculentum Mill. cv. Ailsa Craig) plants were grown with roots split between two soil columns. After plant establishment, water was applied daily to one (partial root-zone drying-PRD) or both (well-watered control-WW) columns. Water was withheld from the other column in the PRD treatment, to expose some roots to drying soil. Soil and plant water status were monitored daily and throughout diurnal courses. Over 8 d, there were no treatment differences in leaf water potential (psileaf) even though soil moisture content of the upper 6 cm (theta) of the dry column in the PRD treatment decreased by up to 70%. Stomatal conductance (gs) of PRD plants decreased (relative to WW plants) when of the dry column decreased by 45%. Such closure coincided with increased xylem sap pH and did not require increased xylem sap abscisic acid (ABA) concentration ([X-ABA]). Detached leaflet ethylene evolution of PRD plants increased when of the dry column decreased by 55%, concurrent with decreased leaf elongation. The physiological significance of enhanced ethylene evolution of PRD plants was examined using a transgenic tomato (ACO1AS) with low stress-induced ethylene production. In response to PRD, ACO1AS and wild-type plants showed similar xylem sap pH, [X-ABA] and gs, but ACO1AS plants showed neither enhanced ethylene evolution nor significant reductions in leaf elongation. Combined use of genetic technologies to reduce ethylene production and agronomic technologies to sustain water status (such as PRD) may sustain plant growth under conditions where yield would otherwise be significantly reduced.     

A genomewide search finds major susceptibility loci for gallbladder disease on chromosome 1 in Mexican Americans

Gallbladder disease (GBD) is one of the major digestive diseases. Its risk factors include age, sex, obesity, type 2 diabetes, and metabolic syndrome (MS). The prevalence of GBD is high in minority populations, such as Native and Mexican Americans. Ethnic differences, familial aggregation of GBD, and the identification of susceptibility loci for gallstone disease by use of animal models suggest genetic influences on GBD. However, the major susceptibility loci for GBD in human populations have not been identified. Using ultrasound-based information on GBD occurrence and a 10-cM gene map, we performed multipoint variance-components analysis to localize susceptibility loci for GBD. Phenotypic and genotypic data from 715 individuals in 39 low-income Mexican American families participating in the San Antonio Family Diabetes/Gallbladder Study were used. Two GBD phenotypes were defined for the analyses: (1) clinical or symptomatic GBD, the cases of cholecystectomies due to stones confirmed by ultrasound, and (2) total GBD, the clinical GBD cases plus the stone carriers newly diagnosed by ultrasound. With use of the National Cholesterol Education Program/Adult Treatment Panel III criteria, five MS risk factors were defined: increased waist circumference, hypertriglyceredemia, low high-density lipoprotein cholesterol, hypertension, and high fasting glucose. The MS risk-factor score (range 0-5) for a given individual was used as a single, composite covariate in the genetic analyses. After accounting for the effects of age, sex, and MS risk-factor score, we found stronger linkage signals for the symptomatic GBD phenotype. The highest LOD scores (3.7 and 3.5) occurred on chromosome 1p between markers D1S1597 and D1S407 (1p36.21) and near marker D1S255 (1p34.3), respectively. Other genetic locations (chromosomes 2p, 3q, 4p, 8p, 9p, 10p, and 16q) across the genome exhibited some evidence of linkage (LOD >or=1.2) to symptomatic GBD. Some of these chromosomal regions corresponded with the genetic locations of Lith loci, which influence gallstone formation in mouse models. In conclusion, we found significant evidence of major genetic determinants of symptomatic GBD on chromosome 1p in Mexican Americans.     

Mitochondrial defects and oxidative damage in patients with peripheral arterial disease

Abnormal mitochondrial function is present in patients with peripheral arterial disease and may contribute to its clinical manifestations. However, the specific biochemical mitochondrial defects and their association with increased oxidative stress have not been fully characterized. Gastrocnemius muscle was obtained from peripheral arterial disease patients (n = 25) and age-matched controls (n = 16) and mitochondrial parameters were measured. Complexes I through IV of the electron transport chain were individually evaluated to assess for isolated defects. Muscle was also evaluated for protein and lipid oxidative changes by measuring the levels of protein carbonyls, lipid hydroperoxides, and total 4-hydroxy-2-nonenal binding and for the activities of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase. Mitochondrial electron transport chain complexes I, III, and IV in arterial disease patients demonstrated significant reductions in enzymatic activities and mitochondrial respiration compared to controls. Oxidative stress biomarker analysis demonstrated significantly increased levels of protein carbonyls, lipid hydroperoxides, and 4-hydroxy-2-nonenal compared to control muscle. Antioxidant enzyme activities were altered, with a significant decrease in superoxide dismutase activity and significant increases in catalase and glutathione peroxidase. Peripheral arterial disease is associated with abnormal mitochondrial function and evidence of significant oxidative stress.     

Selective loss of synaptic proteins in Alzheimer's disease: evidence for an increased severity with APOE varepsilon4

A pathological feature of Alzheimer's disease (AD) is an area-specific neuronal loss that may be caused by excitotoxicity-related synaptic dysfunction. Relative expression levels of synaptophysin, dynamin I, complexins I and II, N-cadherin, and alphaCaMKII were analysed in human brain tissue from AD cases and controls in hippocampus, and inferior temporal and occipital cortices. Synaptophysin and dynamin I are presynaptic terminal proteins not specific to any neurotransmitter system whereas complexin II, N-cadherin, and alphaCaMKII are specific for excitatory synapses. Complexin I is a presynaptic protein localised to inhibitory synapses. There were no significant differences in synaptophysin, dynamin I, N-cadherin, or alphaCaMKII protein levels between AD cases and controls. The complexin proteins were both markedly lower in AD cases than in controls (P < 0.01). Cases were also categorised by APOE genotype. Averaged across areas there was a 36% lowering of presynaptic proteins in AD cases carrying at least one epsilon4 allele compared with in AD cases lacking the epsilon4 allele. We infer that synaptic protein level is not indicative of neuronal loss, but the synaptic dysfunction may result from the marked relative loss of the complexins in AD, and lower levels of presynaptic proteins in AD cases with the APOE epsilon4 allele.     

Different native arbuscular mycorrhizal fungi influence the coexistence of two plant species in a highly alkaline anthropogenic sediment

Different species of arbuscular mycorrhizal fungi (AMF) can produce different amounts of extraradical mycelium (ERM) with differing architectures. They also have different efficiencies in gathering phosphate from the soil. These differences in phosphate uptake and ERM length or architecture may contribute to differential growth responses of plants and this may be an important contributor to plant species coexistence. The effects of the development of the ERM of AMF on the coexistence of two co-occurring plant species were investigated in root-free hyphal chambers in a rhizobox experimental unit. The dominant shrub (Salix atrocinerea Brot.) and herbaceous (Conyza bilbaoana J. Rémy) plant species found in a highly alkaline anthropogenic sediment were studied in symbiosis with four native AMF species (Glomus intraradices BEG163, Glomus mosseae BEG198, Glomus geosporum BEG199 and Glomus claroideum BEG210) that were the most abundant members of the AMF community found in the sediment. Different AMF species did not influence total plant productivity (sum of the biomass of C. bilbaoana and S. atrocinerea), but had a great impact on the individual biomass of each plant species. The AMF species with greater extracted ERM lengths (G. mosseae BEG198, G. claroideum BEG210 and the four mixed AMF) preferentially benefited the plant species with a high mycorrhizal dependency (C. bilbaoana), while the AMF species with the smallest ERM length (G. geosporum BEG199) benefited the plant species with a low mycorrhizal dependency (S. atrocinerea). Seed production of C. bilbaoana was only observed in plants inoculated with G. mosseae BEG198, G. claroideum BEG210 or the mixture of the four AMF. Our results show that AMF play an important role in the reproduction of C. bilbaoana coexisting with S. atrocinerea in the alkaline sediment and have the potential to stimulate or completely inhibit seed production. The community composition of native AMF and the length of the mycelium they produce spreading from roots into the surrounding soil can be determinant of the coexistence of naturally co-occurring plant species.     

Occurrence of sep insecticidal toxin complex genes in Serratia spp. and Yersinia frederiksenii

Some strains of Serratia entomophila and S. proteamaculans cause amber disease of the grass grub Costelytra zealandica (Coleoptera: Scarabaeidae). Three genes required for virulence, sepABC, are located on a large plasmid, pADAP. Sequence analysis suggests that the sepABC gene cluster may be part of a horizontally mobile region. This study presents evidence for the putative mobility of the sep genes of pADAP. Southern blot analysis showed that orthologues of the sep genes reside on plasmids within S. entomophila, S. liquefaciens, S. proteamaculans, and a plasmid from Yersinia frederiksenii. Three plasmids hybridized to the pADAP sep virulence-associated region but not the pADAP replication and conjugation regions. Subsequent DNA sequence analysis of the Y. frederiksenii sep-like genes, designated tcYF1 and tcYF2, showed that they had 88% and 87% DNA identity to sepA and sepB, respectively. These results indicate that the sep genes are part of a discrete horizontally mobile region.     

Biodiversity vs. biocontrol: positive and negative effects of alternative prey on control of slugs by carabid beetles

Environment-friendly farming techniques seek to increase invertebrate biodiversity in part with the intention of encouraging greater numbers of predators that will help to control crop pests. However, in theory, this effect may be negated if the availability of a greater abundance and diversity of alternative prey diverts predators away from feeding on pests. The hypothesis that access to alternative prey can lead to reduced pest suppression under semi-field conditions was tested. Alternative prey type and diversity were manipulated in 70 mesocosms over 7+ weeks in the presence of the carabid Pterostichus melanarius (Illiger), a known predator of slugs, and reproducing populations of the slug Deroceras reticulatum (Müller). Significantly fewer slugs survived where no alternative prey were provided. Maximum slug numbers and biomass were found in treatments containing either carabids plus a high diversity of alternative prey (many species of earthworm and three of Diptera larvae) or a single additional prey (blowfly larvae, Calliphora vomitoria Linnaeus). In these treatments slug numbers and biomass were as high as in plots lacking predators. The effects of alternative prey were taxon-specific. Alternative prey strongly affected carabid fitness in terms of biomass and egg load. The fittest predators (those with access to high alternative prey diversity or C. vomitoria larvae) reduced slug numbers the least. The mean individual slug weights were greater in treatments with alternative prey than where no alternative prey were provided to the carabids. These results suggest that pests may survive and reproduce more rapidly in patches where predators have access to alternative prey.