The effects of introduced plants on songbird reproductive success

The effects of non-native plants on habitat use are well studied; however, whether introduced plants negatively influence reproductive output of animal populations has received much less attention. We conducted a systematic literature review to evaluate the influence of non-native plants on reproductive performance in songbirds. Our global search resulted in 32 relevant articles, from which we compiled a dataset of 133 songbird responses to nesting in or around non-native vegetation. Reproductive metrics examined included measures of nest survival/mortality, productivity, fledgling survival, adult survival, nestling condition, and brood parasitism. Thirty-five percent of songbird reproductive responses were negative (n = 47), with 31% positive (n = 41) and 34% neutral (n = 45) responses found. Only 15% of responses were statistically significant effects (n = 20), and of these, negative effects were reported three times as often as positive effects. Non-significant trends were more prevalent (51% of responses), and the frequency of negative and positive trends was similar. The probability of finding a negative response (significant effect or non-significant trend) was higher for birds using introduced shrubs and wetland habitats. Mechanisms underlying responses were diverse, though similar drivers, such as differences in vegetation characteristics, predation pressure, and resource availability, were offered to explain both positive and negative effects. We found evidence for non-native plants as ecological traps in 39% of articles that assessed these phenomena (n = 16). This review highlights the sparsity of research targeting reproductive responses to plant invasion and synthesizes existing information to enhance our understanding of how birds respond to non-native plants. Our findings could be used to inform future research priorities in a world increasingly dominated by novel ecosystems.     

Comparing the Ecological Impacts of Wind and Oil & Gas Development: A Landscape Scale Assessment

Energy production in the United States is in transition as the demand for clean and domestic power increases. Wind energy offers the benefit of reduced emissions, yet, like oil and natural gas, it also contributes to energy sprawl. We used a diverse set of indicators to quantify the ecological impacts of oil, natural gas, and wind energy development in Colorado and Wyoming. Aerial imagery was supplemented with empirical data to estimate habitat loss, fragmentation, potential for wildlife mortality, susceptibility to invasion, biomass carbon lost, and water resources. To quantify these impacts we digitized the land-use footprint within 375 plots, stratified by energy type. We quantified the change in impacts per unit area and per unit energy produced, compared wind energy to oil and gas, and compared landscapes with and without energy development. We found substantial differences in impacts between energy types for most indicators, although the magnitude and direction of the differences varied. Oil and gas generally resulted in greater impacts per unit area but fewer impacts per unit energy compared with wind. Biologically important and policy-relevant outcomes of this study include: 1) regardless of energy type, underlying land-use matters and development in already disturbed areas resulted in fewer total impacts; 2) the number and source of potential mortality varied between energy types, however, the lack of robust mortality data limits our ability to use this information to estimate and mitigate impacts; and 3) per unit energy produced, oil and gas extraction was less impactful on an annual basis but is likely to have a much larger cumulative footprint than wind energy over time. This rapid evaluation of landscape-scale energy development impacts could be replicated in other regions, and our specific findings can help meet the challenge of balancing land conservation with society’s demand for energy.     

Mutual regulation of plant phospholipase D and the actin cytoskeleton

Membrane lipids and cytoskeleton dynamics are intimately inter‐connected in the eukaryotic cell; however, only recently have the molecular mechanisms operating at this interface in plant cells been addressed experimentally. Phospholipase D (PLD) and its product phosphatidic acid (PA) were discovered to be important regulators in the membrane–cytoskeleton interface in eukaryotes. Here we report the mechanistic details of plant PLD–actin interactions. Inhibition of PLD by n‐butanol compromises pollen tube actin, and PA rescues the detrimental effect of n‐butanol on F‐actin, showing clearly the importance of the PLD–PA interaction for pollen tube F‐actin dynamics. From various candidate tobacco PLDs isoforms, we identified NtPLDβ1 as a regulatory partner of actin, by both activity and in vitro interaction assays. Similarly to published data, the activity of tobacco PIP₂‐dependent PLD (PLDβ) is specifically enhanced by F‐actin and inhibited by G‐actin. We then identified the NtPLDβ1 domain responsible for actin interactions. Using sequence‐ and structure‐based analysis, together with site‐directed mutagenesis, we identified Asn323 and Thr382 of NtPLDβ1 as the crucial amino acids in the actin‐interacting fold. The effect of antisense‐mediated suppression of NtPLDβ1 or NtPLDδ on pollen tube F‐actin dynamics shows that NtPLDβ1 is the active partner in PLD–actin interplay. The positive feedback loop created by activation of PLDβ by F‐actin and of F‐actin by PA provides an important mechanism to locally increase membrane–F‐actin dynamics in the cortex of plant cells.     

A dissipative particle dynamics model of carbon nanotubes

A mesoscale dissipative particle dynamics model of single wall carbon nanotubes (CNTs) is designed and demonstrated. The coarse-grained model is produced by grouping together carbon atoms and by bonding the new lumped particles through pair and triplet forces. The mechanical properties of the simulated tube are determined by the bonding forces, which are derived by virtual experiments. Through the introduction of van der Waals interactions, tube–tube interactions were studied. Owing to the reduced number of particles, this model allows the simulation of relatively large systems. The applicability of the presented scheme to model CNT based mechanical devices is discussed.     

Cobalt(2+) binding to human and tomato copper chaperone for superoxide dismutase: implications for the metal ion transfer mechanism

The copper chaperone for superoxide dismutase (CCS) gene encodes a protein that is believed to deliver copper ions specifically to copper-zinc superoxide dismutase (CuZnSOD). CCS proteins from different organisms share high sequence homology and consist of three distinct domains; a CuZnSOD-like central domain 2 flanked by domains 1 and 3, which contain putative metal-binding motifs. We report deduced protein sequences from tomato and Arabidopsis, the first functional homologues of CCS identified in plants. We have purified recombinant human (hCCS) and tomato (tCCS) copper chaperone proteins, as well as a truncated version of tCCS containing only domains 2 and 3. Their cobalt(2+) binding properties in the presence and absence of mercury(2+) were characterized by UV-vis and circular dichroism spectroscopies and it was shown that hCCS has the ability to bind two spectroscopically distinct cobalt ions whereas tCCS binds only one. The cobalt binding site that is common to both hCCS and tCCS displayed spectroscopic characteristics of cobalt(2+) bound to four or three cysteine ligands. There are only four cysteine residues in tCCS, two in domain 1 and two in domain 3; all four are conserved in other CCS sequences including hCCS. Thus, an interaction between domain 1 and domain 3 is concluded, and it may be important in the copper chaperone mechanism of these proteins.     

Pharmacokinetic Study of 14-(3-Methylbenzyl)matrine and 14-(4-Methylbenzyl)matrine in Rat Plasma Using Liquid Chromatography-Tandem Mass Spectrometry

A rapid, sensitive and selective high-performance liquid chromatography-tandem mass spectrometric method (HPLC-MS) was developed and validated to determine the 14-(3-methylbenzyl)matrine (3MBM) and 14-(4-methylbenzyl)matrine (4MBM) levels in rat plasma in the present study. The analytes were separated using a C18 column (1.9 μm, 2.1 mm × 100 mm) equipped with a Security Guard C18 column (5 μm, 2.1 mm × 10 mm), followed by detection via triple-quadrupole mass spectrometry using an electrospray ionization (ESI) source. Sample pretreatment involved one-step protein precipitation with isopropanol:ethyl acetate (v/v, 25:75), and pseudoephedrine hydrochloride was used as an internal standard. The method was linear in the concentration range of 5–2000 ng/ml for both compounds. The intra-day and inter-day relative standard deviations (RSDs) were less than 15%, and all relative errors (REs) were within 15%. The proposed method enables the unambiguous identification and quantification of these two compounds in vivo. This study is the first to determine the 3MBM and 4MBM levels in rat plasma after oral administration of these compounds. These results provide a meaningful basis for evaluating the clinical applications of these medicines.     

Aluminum ions alter the function of non-specific phospholipase C through the changes in plasma membrane physical properties

The first indication of the aluminum (Al) toxicity in plants growing in acidic soils is the cessation of root growth, but the detailed mechanism of Al effect is unknown. Here we examined the impact of Al stress on the activity of non-specific phospholipase C (NPC) in the connection with the processes related to the plasma membrane using fluorescently labeled phosphatidylcholine. We observed a rapid and significant decrease of labeled diacylglycerol (DAG), product of NPC activity, in Arabidopsis seedlings treated with AlCl₃. Interestingly, an application of the membrane fluidizer, benzyl alcohol, restored the level of DAG during Al treatment. Our observations suggest that the activity of NPC is affected by Al-induced changes in plasma membrane physical properties.