Double mutation in Eleusine indica α-tubulin increases the resistance of transgenic maize calli to dinitroaniline and phosphorothioamidate herbicides

The repeated use of dinitroaniline herbicides on the cotton and soybean fields of the southern United States has resulted in the appearance of resistant biotypes of one of the world's worst weeds, Eleusine indica. Two biotypes have been characterized, a highly resistant (R) biotype and an intermediate resistant (I) biotype. In both cases the resistance has been attributed to a mutation in α-tubulin, a component of the α/β tubulin dimer that is the major constituent of microtubules. We show here that the I-biotype mutation, like the R-biotype mutation shown in earlier work, can confer dinitroaniline resistance on transgenic maize calli. The level of resistance obtained is the same as that for E. indica I- or R-biotype seedlings. The combined I- and R-biotype mutations increase the herbicide tolerance of transgenic maize calli by a value close to the summation of the maximum herbicide tolerances of calli harbouring the single mutations. These data, taken together with the position of the two different mutations within the atomic structure of the α/β tubulin dimer, imply that each mutation is likely to exert its effect by a different mechanism. These mechanisms may involve increasing the stability of microtubules against the depolymerizing effects of the herbicide or changing the conformation of the α/β dimer so that herbicide binding is less effective, or a combination of both possibilities.     

Anti-stress activity of Propionibacterium freudenreichii: identification of a reactivative protein

Propionibacterium freudenreichii subsp. shermanii is known to prevent mutations caused by various agents such as N-methyl-N'-nitro-N-nitrosoguanidine, 9-aminoacridine, 4-nitro-quinoline-1-oxide and by UV radiation in both prokaryotic and eukaryotic cells. It was also shown to prevent or repair damage caused by H(2)O(2) or UV radiation in Salmonella typhimurium and Escherichia coli, a characteristic previously designated as reactivative effect. In order to characterise this effect at the molecular level, we have purified the active component from a P. freudenreichii cell-free extract using a combination of ammonium sulfate precipitation, anion-exchange and size-exclusion chromatography. The isolated 35 kDa protein was then identified using both N-terminal and internal peptide sequencing as a cysteine synthase. The latter was localised in the P. freudenreichii proteomic map. It is constitutively expressed but also clearly induced during adaptation to detergent and heat, but not acid, stresses. The biological meaning of cysteine synthase in the context of adaptation to oxidative and non-oxidative stresses is discussed.     

The growth of soybean under free air [CO<Subscript>2</Subscript>] enrichment (FACE) stimulates photosynthesis while decreasing in vivo Rubisco capacity

Down-regulation of light-saturated photosynthesis (A_sat) at elevated atmospheric CO₂ concentration, [CO₂], has been demonstrated for many C₃ species and is often associated with inability to utilize additional photosynthate and/or nitrogen limitation. In soybean, a nitrogen-fixing species, both limitations are less likely than in crops lacking an N-fixing symbiont. Prior studies have used controlled environment or field enclosures where the artificial environment can modify responses to [CO₂]. A soybean free air [CO₂] enrichment (FACE) facility has provided the first opportunity to analyze the effects of elevated [CO₂] on photosynthesis under fully open-air conditions. Potential ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation (V_c,max) and electron transport through photosystem II (J_max) were determined from the responses of A_sat to intercellular [CO₂] (C_i) throughout two growing seasons. Mesophyll conductance to CO₂ (g_m) was determined from the responses of A_sat and whole chain electron transport (J) to light. Elevated [CO₂] increased A_sat by 15–20% even though there was a small, statistically significant, decrease in V_c,max. This differs from previous studies in that V_c,max/J_max decreased, inferring a shift in resource investment away from Rubisco. This raised the C_i at which the transition from Rubisco-limited to ribulose-1,5-bisphosphate regeneration-limited photosynthesis occurred. The decrease in V_c,max was not the result of a change in g_m, which was unchanged by elevated [CO₂]. This first analysis of limitations to soybean photosynthesis under fully open-air conditions reveals important differences to prior studies that have used enclosures to elevate [CO₂], most significantly a smaller response of A_sat and an apparent shift in resources away from Rubisco relative to capacity for electron transport.Abbreviations FACE Free air [CO₂] enrichment - Rubisco Ribulose-1,5-bisphosphate carboxylase/oxygenase - RuBP Ribulose-1,5-bisphosphate - SoyFACE Soybean free air [CO₂] enrichment - VPD Vapor pressure deficit     

Hydroxylated analogues of the orally active broad spectrum antifungal, Sch 51048 (1), and the discovery of posaconazole [Sch 56592; 2 or (S,S)-5

As part of a detailed study, the syntheses, biological activities, and pharmacokinetic properties of hydroxylated analogues of the previously described broad spectrum antifungal agents, Sch 51048 (1), Sch 50001 (3), and Sch 50002 (4), are described. Based on an overall superior profile, one of the alcohols, Sch 56592 (2), was selected for clinical studies.     

Rainfall manipulation experiments as simulated by terrestrial biosphere models: Where do we stand?

Changes in rainfall amounts and patterns have been observed and are expected to continue in the near future with potentially significant ecological and societal consequences. Modelling vegetation responses to changes in rainfall is thus crucial to project water and carbon cycles in the future. In this study, we present the results of a new model‐data intercomparison project, where we tested the ability of 10 terrestrial biosphere models to reproduce the observed sensitivity of ecosystem productivity to rainfall changes at 10 sites across the globe, in nine of which, rainfall exclusion and/or irrigation experiments had been performed. The key results are as follows: (a) Inter‐model variation is generally large and model agreement varies with timescales. In severely water‐limited sites, models only agree on the interannual variability of evapotranspiration and to a smaller extent on gross primary productivity. In more mesic sites, model agreement for both water and carbon fluxes is typically higher on fine (daily–monthly) timescales and reduces on longer (seasonal–annual) scales. (b) Models on average overestimate the relationship between ecosystem productivity and mean rainfall amounts across sites (in space) and have a low capacity in reproducing the temporal (interannual) sensitivity of vegetation productivity to annual rainfall at a given site, even though observation uncertainty is comparable to inter‐model variability. (c) Most models reproduced the sign of the observed patterns in productivity changes in rainfall manipulation experiments but had a low capacity in reproducing the observed magnitude of productivity changes. Models better reproduced the observed productivity responses due to rainfall exclusion than addition. (d) All models attribute ecosystem productivity changes to the intensity of vegetation stress and peak leaf area, whereas the impact of the change in growing season length is negligible. The relative contribution of the peak leaf area and vegetation stress intensity was highly variable among models.     

Behavioral cues associated with oviposition by Trioza eugeniae

Trioza eugeniae oviposited significantly more eggs on Syzygium paniculatum leaves free of eggs compared to leaves with pre-existing eggs in a choice experiment, suggesting that females modify oviposition based on cues associated with the presence of eggs. In separate experiments, females avoided ovipositing on parts of leaves where eggs were present, but readily oviposited on areas of the same leaf without eggs. Epideictic pheromones are apparently not used by this species because females readily oviposited on areas of a leaf from which eggs had previously been removed. Females laid 57% of all their eggs along the margins of normal leaves, but also oviposited on artificial margins produced by cutting the leaves. The preference for natural margins over artificial margins was eliminated when the entire margin was coated with an antitranspirant compound to mask the damaged edge. These studies show that ovipositing psyllids respond both to the presence of eggs and to the suitability of the substrate.     

Perspectives of taste reception

Summary Ion: solute cotransporters frequency are incapable of achieving equilibrium between the solute accumulation and the transmembrane difference of the electrochemical potential of the ion. The presence of uncoupled flows of ion and solutes (leaks) is often advanced as an explanation. Here an alternative is discussed. The net accumulation of solute may be so slow that equilibrium can never be attained at finite times (e.g., several hours). Cotransporters may exhibit strong product inhibition, and the net influx of solute approaches zero far from equilibrium. The inherent slowness of net transport under these conditions is termed catalytic inefficiency. The likelihood that galactoside: H⁺ cotransport inEscherichia coli, hexose: H⁺ cotransport inChlorella vulgaris, andd-glucose: Na⁺ cotransport in brush-border membranes exhibit catalytic inefficiency is examined. The existence of strong product inhibition complicates the determination of the stoichiometry of cotransport and the characterization of chemically modified or mutant cotransporters.     

Long-term cathode performance and the microbial communities that develop in microbial fuel cells fed different fermentation endproducts

To better understand how cathode performance and substrates affected communities that evolved in these reactors over long periods of time, microbial fuel cells were operated for more than 1 year with individual endproducts of lignocellulose fermentation (acetic acid, formic acid, lactic acid, succinic acid, or ethanol). Large variations in reactor performance were primarily due to the specific substrates, with power densities ranging from 835 ± 21 to 62 ± 1 mW/m³. Cathodes performance degraded over time, as shown by an increase in power of up to 26% when the cathode biofilm was removed, and 118% using new cathodes. Communities that developed on the anodes included exoelectrogenic families, such as Rhodobacteraceae, Geobacteraceae, and Peptococcaceae, with the Deltaproteobacteria dominating most reactors. Pelobacter propionicus was the predominant member in reactors fed acetic acid, and it was abundant in several other MFCs. These results provide valuable insights into the effects of long-term MFC operation on reactor performance.     

The production of artemisinin precursors in tobacco

Artemisinin, in the form of artemisinin‐based combination therapies (ACTs), is currently the most important compound in the treatment of malaria. The current commercial source of artemisinin is Artemisia annua, but this represents a relatively expensive source for supplying the developing world. In this study, the possibility of producing artemisinin in genetically modified plants is investigated, using tobacco as a model. Heterologous expression of A. annua amorphadiene synthase and CYP71AV1 in tobacco led to the accumulation of amorphadiene and artemisinic alcohol, but not artemisinic acid. Additional expression of artemisinic aldehyde Δ11(13) double‐bond reductase (DBR2) with or without aldehyde dehydrogenase 1 (ALDH1) led to the additional accumulation dihydroartemisinic alcohol. The above‐mentioned results and in vivo metabolic experiments suggest that amorphane sesquiterpenoid aldehydes are formed, but conditions in the transgenic tobacco cells favour reduction to alcohols rather than oxidation to acids. The biochemical and biotechnological significance of these results are discussed.