Effect of Soil pH on Growth and Cation Deposition in the Root Tip of <Emphasis Type="BoldItalic">Zea mays</Emphasis> L.

Abstract The effects of sandy soil pH on the distribution of growth velocities and on cation concentrations and deposition rates in root growth zones of Zea mays L. seedlings were investigated. The pH values of the rooting medium varied between 4.2 and 8.6 in sand culture (70% saturated) without external supply of nutrients. At all pH values, densities (in 7moles per g fresh weight) of potassium, magnesium, and calcium increased toward the root tip. Lower pH in the medium increased calcium tissue density fivefold and magnesium density 1.7-fold, whereas the density of potassium, the overall elongation rate, and the growth velocity distribution did not show any significant pH dependence. Throughout the growth zone the deposition rates of the divalent cations, as calculated on the basis of the continuity equation, increased with lower pH. The data are consistent with the hypothesis that the effects of pH on the cation deposition rates are due to the increase in the divalent cation concentration of the soil solution at low pH and that the abundant uronic acid residues of the young walls of the meristem provide a reservoir of storage capacity for Ca and Mg under conditions of low nutrient availability.     

Large-Scale Variations in Lumber Value Recovery of Yellow Birch and Sugar Maple in Quebec,Canada

Silvicultural restoration measures have been implemented in the northern hardwoods forests of southern Quebec, Canada, but their financial applicability is often hampered by the depleted state of the resource. To help identify sites most suited for the production of high quality timber, where the potential return on silvicultural investments should be the highest, this study assessed the impact of stand and site characteristics on timber quality in sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britt.). For this purpose, lumber value recovery (LVR), an estimate of the summed value of boards contained in a unit volume of round wood, was used as an indicator of timber quality. Predictions of LVR were made for yellow birch and sugar maple trees contained in a network of more than 22000 temporary sample plots across the Province. Next, stand-level variables were selected and models to predict LVR were built using the boosted regression trees method. Finally, the occurrence of spatial clusters was verified by a hotspot analysis. Results showed that in both species LVR was positively correlated with the stand age and structural diversity index, and negatively correlated with the number of merchantable stems. Yellow birch had higher LVR in areas with shallower soils, whereas sugar maple had higher LVR in regions with deeper soils. The hotspot analysis indicated that clusters of high and low LVR exist across the province for both species. Although it remains uncertain to what extent the variability of LVR may result from variations in past management practices or in inherent site quality, we argue that efforts to produce high quality timber should be prioritized in sites where LVR is predicted to be the highest.     

Therapeutic antibody engineering by high efficiency cell screening

In recent years, several cell-based screening technologies for the isolation of antibodies with prescribed properties emerged. They rely on the multi-copy display of antibodies or antibody fragments on a cell surface in functional form followed by high through put screening and isolation of cell clones that carry an antibody variant with the desired affinity, specificity, and stability. Particularly yeast surface display in combination with high-throughput fluorescence-activated cell sorting has proven successful in the last fifteen years as a very powerful technology that has some advantages over classical generation of monoclonals using the hybridoma technology or bacteriophage-based antibody display and screening. Cell-based screening harbours the benefit of single-cell online and real-time analysis and characterisation of individual library candidates. Moreover, when using eukaryotic expression hosts, intrinsic quality control machineries for proper protein folding and stability exist that allow for co-selection of high-level expression and stability simultaneously to the binding functionality. Recently, promising technologies emerged that directly rely on antibody display on higher eukaryotic cell lines using lentiviral transfection or direct screening on B-cells. The combination of immunisation, B-cell screening and next generation sequencing may open new avenues for the isolation of therapeutic antibodies with prescribed physicochemical and functional characteristics.     

Quantitative analysis of processive RNA degradation by the archaeal RNA exosome

RNA exosomes are large multisubunit assemblies involved in controlled RNA processing. The archaeal exosome possesses a heterohexameric processing chamber with three RNase-PH-like active sites, capped by Rrp4- or Csl4-type subunits containing RNA-binding domains. RNA degradation by RNA exosomes has not been studied in a quantitative manner because of the complex kinetics involved, and exosome features contributing to efficient RNA degradation remain unclear. Here we derive a quantitative kinetic model for degradation of a model substrate by the archaeal exosome. Markov Chain Monte Carlo methods for parameter estimation allow for the comparison of reaction kinetics between different exosome variants and substrates. We show that long substrates are degraded in a processive and short RNA in a more distributive manner and that the cap proteins influence degradation speed. Our results, supported by small angle X-ray scattering, suggest that the Rrp4-type cap efficiently recruits RNA but prevents fast RNA degradation of longer RNAs by molecular friction, likely by RNA contacts to its unique KH-domain. We also show that formation of the RNase-PH like ring with entrapped RNA is not required for high catalytic efficiency, suggesting that the exosome chamber evolved for controlled processivity, rather than for catalytic chemistry in RNA decay.     

Spatial,temporal and interindividual epigenetic variation of functionally important DNA methylation patterns

DNA methylation is an epigenetic modification that plays an important role in gene regulation. It can be influenced by stochastic events, environmental factors and developmental programs. However, little is known about the natural variation of gene-specific methylation patterns. In this study, we performed quantitative methylation analyses of six differentially methylated imprinted genes (H19, MEG3, LIT1, NESP55, PEG3 and SNRPN), one hypermethylated pluripotency gene (OCT4) and one hypomethylated tumor suppressor gene (APC) in chorionic villus, fetal and adult cortex, and adult blood samples. Both average methylation level and range of methylation variation depended on the gene locus, tissue type and/or developmental stage. We found considerable variability of functionally important methylation patterns among unrelated healthy individuals and a trend toward more similar methylation levels in monozygotic twins than in dizygotic twins. Imprinted genes showed relatively little methylation changes associated with aging in individuals who are >25 years. The relative differences in methylation among neighboring CpGs in the generally hypomethylated APC promoter may not only reflect stochastic fluctuations but also depend on the tissue type. Our results are consistent with the view that most methylation variation may arise after fertilization, leading to epigenetic mosaicism.     

Respiratory proteins in Sipunculus nudus — Implications for phylogeny and evolution of the hemerythrin family

Three major classes of respiratory proteins are known, hemoglobin, molluscan and arthropod hemocyanin, and hemerythrin (Hr). Similar to hemoglobin, respiratory Hr is packed into erythrocytes floating in the coelomic fluid and is only known from sipunculids, brachiopods, and priapulids. Owing to this scattered distribution, the presence of Hr is generally assumed to be the plesiomorphic condition without phylogenetic importance. By sequencing 2000 Expressed Sequence Tags (ESTs) from Sipunculus nudus, we found 75 Hr-coding ESTs assembled to 20 cDNA contigs classified as four distinct Hr isoforms: three polymeric Hrs (subunit A, A', and B) and the monomeric myo-hemerythrin (myoHr). Phylogenetic analyses revealed a clade of annelid and sipunculan monomeric Hrs, distinct from polymeric Hrs. Monomeric Hrs from annelids and sipunculids can be clustered together using Maximum Likelihood tree-building and network analyses, as well as applying Bayesian methods. Three distinct Hr clusters were found for S. nudus, suggesting a new monomeric Hr isoform.     

In vivo and in vitro SAR of tetracyclic MAPKAP-K2 (MK2) inhibitors. Part II

Spirocyclopropane- and spiroazetidine-substituted tetracycles 13D–E and 16A are described as orally active MK2 inhibitors. The spiroazetidine derivatives are potent MK2 inhibitors with IC₅₀ <3 nM and inhibit the release of TNFα (IC₅₀<0.3 μM) from hPBMCs and hsp27 phosphorylation in anisomycin stimulated THP-1 cells. The spirocyclopropane analogues are less potent against MK2 (IC₅₀ = 0.05–0.23 μM), less potent in cells (IC₅₀ <1.1 μM), but show good oral absorption. Compound 13E (100 mg/kg po; bid) showed oral activity in rAIA and mCIA, with significant reduction of swelling and histological score.     

Transgenic apple plants overexpressing the Lc gene of maize show an altered growth habit and increased resistance to apple scab and fire blight

Transgenic apple plants (Malus × domestica cv. ‘Holsteiner Cox’) overexpressing the Leaf Colour (Lc) gene from maize (Zea mays) exhibit strongly increased production of anthocyanins and flavan-3-ols (catechins, proanthocyanidins). Greenhouse plants investigated in this study exhibit altered phenotypes with regard to growth habit and resistance traits. Lc-transgenic plants show reduced size, transversal gravitropism of lateral shoots, reduced trichome development, and frequently reduced shoot diameter and abnormal leaf development with fused leaves. Such phenotypes seem to be in accordance with a direct or an indirect effect on polar-auxin-transport in the transgenic plants. Furthermore, leaves often develop necrotic lesions resembling hypersensitive response lesions. In tests, higher resistance against fire blight (caused by the bacterium Erwinia amylovora) and against scab (caused by the fungus Venturia inaequalis) is observed. These phenotypes are discussed with respect to the underlying altered physiology of the Lc-transgenic plants. The results are expected to be considered in apple breeding strategies.     

The likely impact of elevated [CO2], nitrogen deposition, increased temperature and management on carbon sequestration in temperate and boreal forest ecosystems: a literature review

Temperate and boreal forest ecosystems contain a large part of the carbon stored on land, in the form of both biomass and soil organic matter. Increasing atmospheric [CO2], increasing temperature, elevated nitrogen deposition and intensified management will change this C store. Well documented single-factor responses of net primary production are: higher photosynthetic rate (the main [CO2] response); increasing length of growing season (the main temperature response); and higher leaf-area index (the main N deposition and partly [CO2] response). Soil organic matter will increase with increasing litter input, although priming may decrease the soil C stock initially, but litter quality effects should be minimal (response to [CO2], N deposition, and temperature); will decrease because of increasing temperature; and will increase because of retardation of decomposition with N deposition, although the rate of decomposition of high-quality litter can be increased and that of low-quality litter decreased. Single-factor responses can be misleading because of interactions between factors, in particular those between N and other factors, and indirect effects such as increased N availability from temperature-induced decomposition. In the long term the strength of feedbacks, for example the increasing demand for N from increased growth, will dominate over short-term responses to single factors. However, management has considerable potential for controlling the C store.