Nitrogen response efficiency of a managed and phytodiverse temperate grassland

Aims

Our goal was to assess how management and sward functional diversity affect nitrogen response efficiency (NRE), the ratio of plant biomass production to supply of available nitrogen (N) in temperate grassland.

Methods

A three-factorial design was employed: three sward compositions, two mowing frequencies, and two fertilization treatments.

Results

NRE was largely influenced by fertilization followed by mowing frequency and sward composition. NRE was larger in unfertilized than fertilized plots, in plots cut thrice than plots cut once per year, and in control swards than in monocot- or dicot-enhanced swards. Fertilization decreased NRE through decreases in both N uptake efficiency (plant N uptake per supply of available N) and N use efficiency (NUE, biomass produced per plant N uptake) whereas mowing frequency and sward composition affected NRE through N uptake efficiency rather than NUE. The largest NRE in the control sward with 70 % monocots and 30 % dicots attests that these proportions of functional groups were best adapted in this grassland ecosystem.

Conclusions

Optimum NRE may not be a target of most farmers, but it is an appropriate tool to evaluate the consequences of grassland management practices, which farmers may employ to maximize profit, on environmental quality.     

Low sodium isocyanurate concentrations as a substitute to medium autoclaving in plant tissue culture

Plant Cell, Tissue and Organ Culture (PCTOC) - An optimization for a medium sterilization method, capable of substituting autoclaving, was developed using low concentrations of sodium isocyanurate...     

Ecological dynamics of emerging bat virus spillover

Viruses that originate in bats may be the most notorious emerging zoonoses that spill over from wildlife into domestic animals and humans. Understanding how these infections filter through ecological systems to cause disease in humans is of profound importance to public health. Transmission of viruses from bats to humans requires a hierarchy of enabling conditions that connect the distribution of reservoir hosts, viral infection within these hosts, and exposure and susceptibility of recipient hosts. For many emerging bat viruses, spillover also requires viral shedding from bats, and survival of the virus in the environment. Focusing on Hendra virus, but also addressing Nipah virus, Ebola virus, Marburg virus and coronaviruses, we delineate this cross-species spillover dynamic from the within-host processes that drive virus excretion to land-use changes that increase interaction among species. We describe how land-use changes may affect co-occurrence and contact between bats and recipient hosts. Two hypotheses may explain temporal and spatial pulses of virus shedding in bat populations: episodic shedding from persistently infected bats or transient epidemics that occur as virus is transmitted among bat populations. Management of livestock also may affect the probability of exposure and disease. Interventions to decrease the probability of virus spillover can be implemented at multiple levels from targeting the reservoir host to managing recipient host exposure and susceptibility.     

Mechanisms of rapid induction of interleukin-22 in activated T cells and its modulation by cyclosporin a

IL-22 is an immunoregulatory cytokine displaying pathological functions in models of autoimmunity like experimental psoriasis. Understanding molecular mechanisms driving IL-22, together with knowledge on the capacity of current immunosuppressive drugs to target this process, may open an avenue to novel therapeutic options. Here, we sought to characterize regulation of human IL22 gene expression with focus on the established model of Jurkat T cells. Moreover, effects of the prototypic immunosuppressant cyclosporin A (CsA) were investigated. We report that IL-22 induction by TPA/A23187 (T/A) or αCD3 is inhibited by CsA or related FK506. Similar data were obtained with peripheral blood mononuclear cells or purified CD3(+) T cells. IL22 promoter analysis (-1074 to +156 bp) revealed a role of an NF-AT (-95/-91 nt) and a CREB (-194/-190 nt) binding site for gene induction. Indeed, binding of CREB and NF-ATc2, but not c-Rel, under the influence of T/A to those elements could be proven by ChIP. Because CsA has the capability to impair IκB kinase (IKK) complex activation, the IKKα/β inhibitor IKKVII was evaluated. IKKVII likewise reduced IL-22 induction in Jurkat cells and peripheral blood mononuclear cells. Interestingly, transfection of Jurkat cells with siRNA directed against IKKα impaired IL22 gene expression. Data presented suggest that NF-AT, CREB, and IKKα contribute to rapid IL22 gene induction. In particular the crucial role of NF-AT detected herein may form the basis of direct action of CsA on IL-22 expression by T cells, which may contribute to therapeutic efficacy of the drug in autoimmunity.     

Evidence for statistical epistasis between catechol-<Emphasis Type="Italic">O</Emphasis>-methyltransferase (COMT) and polymorphisms in RGS4, G72 (DAOA), GRM3, and DISC1: influence on risk of schizophrenia

Catechol-O-methyltransferase (COMT) regulates dopamine degradation and is located in a genomic region that is deleted in a syndrome associated with psychosis, making it a promising candidate gene for schizophrenia. COMT also has been shown to influence prefrontal cortex processing efficiency. Prefrontal processing dysfunction is a common finding in schizophrenia, and a background of inefficient processing may modulate the effect of other candidate genes. Using the NIMH sibling study (SS), a non-independent case-control set, and an independent German (G) case-control set, we performed conditional/unconditional logistic regression to test for epistasis between SNPs in COMT (rs2097603, Val158Met (rs4680), rs165599) and polymorphisms in other schizophrenia susceptibility genes. Evidence for interaction was evaluated using a likelihood ratio test (LRT) between nested models. SNPs in RGS4, G72, GRM3, and DISC1 showed evidence for significant statistical epistasis with COMT. A striking result was found in RGS4: three of five SNPs showed a significant increase in risk [LRT P-values: 90387 = 0.05 (SS); SNP4 = 0.02 (SS), 0.02 (G); SNP18 = 0.04 (SS), 0.008 (G)] in interaction with COMT; main effects for RGS4 SNPs were null. Significant results for SNP4 and SNP18 were also found in the German study. We were able to detect statistical interaction between COMT and polymorphisms in candidate genes for schizophrenia, many of which had no significant main effect. In addition, we were able to replicate other studies, including allelic directionality. The use of epistatic models may improve replication of psychiatric candidate gene studies.     

Hfq Influences Multiple Transport Systems and Virulence in the Plant Pathogen Agrobacterium tumefaciens

The Hfq protein mediates gene regulation by small RNAs (sRNAs) in about 50% of all bacteria. Depending on the species, phenotypic defects of an hfq mutant range from mild to severe. Here, we document that the purified Hfq protein of the plant pathogen and natural genetic engineer Agrobacterium tumefaciens binds to the previously described sRNA AbcR1 and its target mRNA atu2422, which codes for the substrate binding protein of an ABC transporter taking up proline and γ-aminobutyric acid (GABA). Several other ABC transporter components were overproduced in an hfq mutant compared to their levels in the parental strain, suggesting that Hfq plays a major role in controlling the uptake systems and metabolic versatility of A. tumefaciens. The hfq mutant showed delayed growth, altered cell morphology, and reduced motility. Although the DNA-transferring type IV secretion system was produced, tumor formation by the mutant strain was attenuated, demonstrating an important contribution of Hfq to plant transformation by A. tumefaciens.     

The Histochemical Localization of Cholesterol in Formalin-Fixed and Fresh Frozen Sections

The premixed cholesterol reagent (acetic acid, sulphuric acid, ferric chloride and phosphoric acid) employed in a spectrophotometric method for serum cholesterol determinations was applied to frozen sections of various rat and rabbit tissues. The histochemical reaction was compared with the results obtained by the classical Schultz reaction. The same bluish-green color was observed after treatment of formalin-fixed and fresh cryostat sections incubated in 2.5% iron alum at 37 C for 3 days. The premixed cholesterol reagent is stable for years at room temperature if stored in a brown bottle and is thus readily available for routine use.