Efficacy and non-target effects of herbicides in foothills grassland restoration are short-lived

Questions

Selective herbicides are frequently used in ecological restoration to control invasive non-native forbs and recover plant communities. However, the long-term efficacy of this practice, its non-target effects on native plants, and its role in facilitating secondary invasions are not well understood. Similarly, little is known about the extent to which herbicide drift may affect native plant communities.

Location

Foothills grasslands of Montana, USA.

Methods

We conducted a 6-year experiment to investigate changes in the abundance of a target invasive plant, knapweed (Centaurea stoebe subsp. micranthos) and plant community structure in response to the herbicides Tordon® (picloram) and Milestone® (aminopyralid), applied at a recommended rate and a diluted rate that simulated drift.

Results

Knapweed cover and the richness of native and non-native forb species declined in the first 3 years in response to treatment at recommended rates, but not drift rates. Secondary invasion by non-native monocots was significant but weak. The cover of native forbs and the cover and richness of native monocots did not differ among treatments but changed significantly with the year. Surprisingly, 6 years after treatments, there were no differences among treatments in the cover of the target invasive plant or community structure.

Conclusions

Our results demonstrate that the efficacy and non-target effects of herbicides in grassland restoration can be short-lived and idiosyncratic because of year effects. Restoration of knapweed invasions might require other active interventions, such as seeding or repeated spraying. Our study supports previous calls for long-term monitoring of herbicides application in ecological restoration.     

The value of cytogenetic monitoring versus film dosimetry in the hot zone of a nuclear power plant.

Cytogenetic analysis was carried out in 41 workers prior to and following regular maintenance work in a nuclear power plant. Although film dosimetry did not show the maximal annual permitted dose in any of the examined subjects, cytogenetic analysis carried out following the work detected dicentric chromosomes in peripheral blood lymphocytes of 20 workers. According to our findings smoking habits and previous exposure to ionizing radiation had no effect on the increased number of chromosomal aberrations.     

Peptide-protein complex from cattle sclera: Structural aspects and chaperone activity

The influence of temperature and chaotropic agents on the spatial organization of the peptide-protein complex isolated from cattle sclera at the level of secondary structure was studied by UV, CD spectroscopy, and dynamic light scattering. It is shown that this complex has high conformational thermostability. The point of conformational thermal transition (65 °C) was determined, after which the peptide-protein complex passes into a denatured stable state. It was found that the peptide-protein complex in aqueous solutions forms thermostable nanosized particles. It was shown that the peptide-protein complex isolated from cattle sclera shows the properties of chaperone, an inhibitor of model protein aggregation induced by dithiothreitol.     

The obstetrical dilemma hypothesis: there's life in the old dog yet

The term ‘obstetrical dilemma’ was coined by Washburn in 1960 to describe the trade-off between selection for a larger birth canal, permitting successful passage of a big-brained human neonate, and the smaller pelvic dimensions required for bipedal locomotion. His suggested solution to these antagonistic pressures was to give birth prematurely, explaining the unusual degree of neurological and physical immaturity, or secondary altriciality, observed in human infants. This proposed trade-off has traditionally been offered as the predominant evolutionary explanation for why human childbirth is so challenging, and inherently risky, compared to that of other primates. This perceived difficulty is likely due to the tight fit of fetal to maternal pelvic dimensions along with the convoluted shape of the birth canal and a comparatively low degree of ligamentous flexibility. Although the ideas combined under the obstetrical dilemma hypothesis originated almost a century ago, they have received renewed attention and empirical scrutiny in the last decade, with some researchers advocating complete rejection of the hypothesis and its assumptions. However, the hypothesis is complex because it presently captures several, mutually non-exclusive ideas: (i) there is an evolutionary trade-off resulting from opposing selection pressures on the pelvis; (ii) selection favouring a narrow pelvis specifically derives from bipedalism; (iii) human neonates are secondarily altricial because they are born relatively immature to ensure that they fit through the maternal bony pelvis; (iv) as a corollary to the asymmetric selection pressure for a spacious birth canal in females, humans evolved pronounced sexual dimorphism of pelvic shape. Recently, the hypothesis has been challenged on both empirical and theoretical grounds. Here, we appraise the original ideas captured under the ‘obstetrical dilemma’ and their subsequent evolution. We also evaluate complementary and alternative explanations for a tight fetopelvic fit and obstructed labour, including ecological factors related to nutrition and thermoregulation, constraints imposed by the stability of the pelvic floor or by maternal and fetal metabolism, the energetics of bipedalism, and variability in pelvic shape. This reveals that human childbirth is affected by a complex combination of evolutionary, ecological, and biocultural factors, which variably constrain maternal pelvic form and fetal growth. Our review demonstrates that it is unwarranted to reject the obstetrical dilemma hypothesis entirely because several of its fundamental assumptions have not been successfully discounted despite claims to the contrary. As such, the obstetrical dilemma remains a tenable hypothesis that can be used productively to guide evolutionary research.     

Quantitative analysis of cell surface antigen-antibody interaction using Gaussia princeps luciferase antibody fusion proteins

Cell surface antigen-specific antibodies are of substantial diagnostic and therapeutic importance. The binding properties of such antibodies are usually evaluated by cell-free assays, in particular surface plasmon resonance (SPR) analysis, or flow cytometry. SPR analyses allow the detailed quantitative and dynamic evaluation of the binding properties of antibodies, but need purified, typically recombinantly produced antigens. It can, however, be difficult to produce the required antigen. Furthermore, cellular factors influencing the antigen-antibody interaction are not considered by this method. Flow cytometry-based analyses do not have these limitations, but require elaborated calibration controls for absolute quantification of bound molecules. To overcome the limitations of SRP and flow cytometry in the characterization of cell surface antigen-specific antibodies, we developed Fn14-specific antibody 18D1 as an example of an antibody fusion protein format that includes the luciferase of Gaussia princeps (GpL), which enables very simple and highly sensitive cellular binding studies. We found that GpL-tagging of the C-terminus of the antibody light chain does not affect the interaction of 18D1-IgG1 with its antigen and Fc-gamma receptors (FcγRs). In accordance with this, the GpL_(LC-CT)-18D1-IgG1 antibody fusion protein showed basically the same FcγR-dependent agonistic properties as the parental 18D1 antibody. Similar results were obtained with isotype switch variants of 18D1 and antibodies specific for CD95, LTβR and CD40. In sum, we demonstrate that antibody GpL fusion proteins are easily manageable and versatile tools for the characterization of cell surface antigen-antibody interactions that have the potential to considerably extend the instrumentarium for the evaluation of antibodies.     

Channelling carbon flux through the meta-cleavage route for improved poly(3-hydroxyalkanoate) production from benzoate and lignin-based aromatics in Pseudomonas putida H

Lignin-based aromatics are attractive raw materials to derive medium-chain length poly(3-hydroxyalkanoates) (mcl-PHAs), biodegradable polymers of commercial value. So far, this conversion has exclusively used the ortho-cleavage route of Pseudomonas putida KT2440, which results in the secretion of toxic intermediates and limited performance. Pseudomonas putida H exhibits the ortho- and the meta-cleavage pathways where the latter appears promising because it stoichiometrically yields higher levels of acetyl-CoA. Here, we created a double-mutant H-ΔcatAΔA2 that utilizes the meta route exclusively and synthesized 30% more PHA on benzoate than the parental strain but suffered from catechol accumulation. The single deletion of the catA2 gene in the H strain provoked a slight attenuation on the enzymatic capacity of the ortho route (25%) and activation of the meta route by nearly 8-fold, producing twice as much mcl-PHAs compared to the wild type. Inline, the mutant H-ΔcatA2 showed a 2-fold increase in the intracellular malonyl-CoA abundance – the main precursor for mcl-PHAs synthesis. As inferred from flux simulation and enzyme activity assays, the superior performance of H-ΔcatA2 benefited from reduced flux through the TCA cycle and malic enzyme and diminished by-product formation. In a benzoate-based fed-batch, P. putida H-ΔcatA2 achieved a PHA titre of 6.1 g l^–1 and a volumetric productivity of 1.8 g l^–1 day^–1. Using Kraft lignin hydrolysate as feedstock, the engineered strain formed 1.4 g l^{- 1} PHA. The balancing of carbon flux between the parallel catechol-degrading routes emerges as an important strategy to prevent intermediate accumulation and elevate mcl-PHA production in P. putida H and, as shown here, sets the next level to derive this sustainable biopolymer from lignin hydrolysates and aromatics.     

Determination of the molecular reach of the protein tyrosine phosphatase SHP-1

Immune receptors signal by recruiting (or tethering) enzymes to their cytoplasmic tails to catalyze reactions on substrates within reach. This is the case for the phosphatase SHP-1, which, upon tethering to inhibitory receptors, dephosphorylates diverse substrates to control T cell activation. Precisely how tethering regulates SHP-1 activity is incompletely understood. Here, we measure binding, catalysis, and molecular reach for tethered SHP-1 reactions. We determine the molecular reach of SHP-1 to be 13.0 nm, which is longer than the estimate from the allosterically active structure (5.3 nm), suggesting that SHP-1 can achieve a longer reach by exploring multiple active conformations. Using modeling, we show that when uniformly distributed, receptor-SHP-1 complexes can only reach 15% of substrates, but this increases to 90% when they are coclustered. When within reach, we show that membrane recruitment increases the activity of SHP-1 by a 1000-fold increase in local concentration. The work highlights how molecular reach regulates the activity of membrane-recruited SHP-1 with insights applicable to other membrane-tethered reactions.