Insulin Receptor Substrate 2-mediated Phosphatidylinositol 3-kinase Signaling Selectively Inhibits Glycogen Synthase Kinase 3β to Regulate Aerobic Glycolysis

Insulin receptor substrate 1 (IRS-1) and IRS-2 are cytoplasmic adaptor proteins that mediate the activation of signaling pathways in response to ligand stimulation of upstream cell surface receptors. Despite sharing a high level of homology and the ability to activate PI3K, only Irs-2 positively regulates aerobic glycolysis in mammary tumor cells. To determine the contribution of Irs-2-dependent PI3K signaling to this selective regulation, we generated an Irs-2 mutant deficient in the recruitment of PI3K. We identified four tyrosine residues (Tyr-649, Tyr-671, Tyr-734, and Tyr-814) that are essential for the association of PI3K with Irs-2 and demonstrate that combined mutation of these tyrosines inhibits glucose uptake and lactate production, two measures of aerobic glycolysis. Irs-2-dependent activation of PI3K regulates the phosphorylation of specific Akt substrates, most notably glycogen synthase kinase 3β (Gsk-3β). Inhibition of Gsk-3β by Irs-2-dependent PI3K signaling promotes glucose uptake and aerobic glycolysis. The regulation of unique subsets of Akt substrates by Irs-1 and Irs-2 may explain their non-redundant roles in mammary tumor biology. Taken together, our study reveals a novel mechanism by which Irs-2 signaling preferentially regulates tumor cell metabolism and adds to our understanding of how this adaptor protein contributes to breast cancer progression.     

Pathway to domestic natural rubber production: a cradle-to-grave life cycle assessment of the first guayule automobile tire manufactured in the United States

The International Journal of Life Cycle Assessment - Guayule (Parthenium argentatum) is a perennial shrub that can be cultivated in the Southwestern US. It produces natural rubber that could be a...     

The effectiveness of flower strips and hedgerows on pest control,pollination services and crop yield: a quantitative synthesis

Floral plantings are promoted to foster ecological intensification of agriculture through provisioning of ecosystem services. However, a comprehensive assessment of the effectiveness of different floral plantings, their characteristics and consequences for crop yield is lacking. Here we quantified the impacts of flower strips and hedgerows on pest control (18 studies) and pollination services (17 studies) in adjacent crops in North America, Europe and New Zealand. Flower strips, but not hedgerows, enhanced pest control services in adjacent fields by 16% on average. However, effects on crop pollination and yield were more variable. Our synthesis identifies several important drivers of variability in effectiveness of plantings: pollination services declined exponentially with distance from plantings, and perennial and older flower strips with higher flowering plant diversity enhanced pollination more effectively. These findings provide promising pathways to optimise floral plantings to more effectively contribute to ecosystem service delivery and ecological intensification of agriculture in the future.     

Population Structure of Clinical and Environmental Vibrio parahaemolyticus from the Pacific Northwest Coast of the United States

Vibrio parahaemolyticus is a common marine bacterium and a leading cause of seafood-borne bacterial gastroenteritis worldwide. Although this bacterium has been the subject of much research, the population structure of cold-water populations remains largely undescribed. We present a broad phylogenetic analysis of clinical and environmental V. parahaemolyticus originating largely from the Pacific Northwest coast of the United States. Repetitive extragenic palindromic PCR (REP-PCR) separated 167 isolates into 39 groups and subsequent multilocus sequence typing (MLST) separated a subset of 77 isolates into 24 sequence types. The Pacific Northwest population exhibited a semi-clonal structure attributed to an environmental clade (ST3, N = 17 isolates) clonally related to the pandemic O3:K6 complex and a clinical clade (ST36, N = 20 isolates) genetically related to a regionally endemic O4:K12 complex. Further, the identification of at least five additional clinical sequence types (i.e., ST43, 50, 65, 135 and 417) demonstrates that V. parahaemolyticus gastroenteritis in the Pacific Northwest is polyphyletic in nature. Recombination was evident as a significant source of genetic diversity and in particular, the recA and dtdS alleles showed strong support for frequent recombination. Although pandemic-related illnesses were not documented during the study, the environmental occurrence of the pandemic clone may present a significant threat to human health and warrants continued monitoring. It is evident that V. parahaemolyticus population structure in the Pacific Northwest is semi-clonal and it would appear that multiple sequence types are contributing to the burden of disease in this region.     

Coccinellid immigration to infested host patches influences suppression of Aphis glycines in soybean

Generalist natural enemies may be well adapted to annual crop systems in which pests and natural enemies re-colonize fields each year. In addition, for patchily-distributed pests, a natural enemy must disperse within a crop field to arrive at infested host patches. As they typically have longer generation times than their prey, theory suggests that generalist natural enemies need high immigration rates to and within fields to effectively suppress pest populations. The soybean aphid, Aphis glycines Matsumura, is a pest of an annual crop and is predominantly controlled by coccinellids. To test if rates of coccinellid arrival at aphid-infested patches are crucial for soybean aphid control, we experimentally varied coccinellid immigration to 1 m² soybean patches using selective barriers and measured effects on A. glycines populations. In a year with low ambient aphid pressure, naturally-occurring levels of coccinellid immigration to host patches were sufficient to suppress aphid populations, while decreasing coccinellid immigration rates resulted in large increases in soybean aphid populations within infested patches. Activity of other predators was low in this year, suggesting that most of the differences in aphid population growth were due to changes in coccinellid immigration. Alternatively, in a year in which alate aphids continually colonized plots, aphid suppression was incomplete and increased activity of other predatory taxa contributed to adult coccinellid predation of A. glycines. Our results suggest that in a system in which natural enemy populations cannot track pest populations through reproduction, immigration of natural enemies to infested patches can compensate and result in pest control.     

Pre-release monitoring of Alliaria petiolata (garlic mustard) invasions and the impacts of extant natural enemies in southern Michigan forests

Monitoring of populations of a target weed species prior to releasing natural enemies has the potential to improve the rigor and safety of biological control and to determine the invader’s impacts on native communities while creating a reference point for evaluating the efficacy of subsequent biocontrol agent releases. Eight populations of garlic mustard, Alliaria petiolata (M. Bieb) Cavara and Grande (Brassicaceae), an invasive weed in southern Michigan, were monitored in anticipation of releases of classical biological control agents. The A. petiolata populations were shown to be expanding with 44.4% of initially uninvaded sampling quadrats becoming invaded after four years. While 88.2% of quadrats with A. petiolata showed evidence of foliar damage from pathogens and browsing by mammals, insects and other invertebrates, levels of damage were low and had little impact on rosette or seedling survival. Contrary to expectations, damage was positively correlated with A. petiolata fecundity (P = 0.0465). Given the continued expansion of A. petiolata and the lack of significant herbivore damage by acquired natural enemies, a biological control program should be considered against this invasive plant. If biological control agents are released, the results of this study will provide a benchmark for evaluating their performance.     

Uncertainty in the Extrapolation from Individual Effects to Impacts upon Landscapes

Uncertainty is inherent in extrapolating from effects upon the individual to alterations in ecological structure or function. Subtle differences in individuals within a population can give rise to significant evolutionary events. Populations are part of ecological structures, systems that are clearly complex, requiring an understanding of the interacting components, stochastic inputs and spatial scales. A series of patch-dynamic models is used to illustrate the importance of spatial arrangement and initial population size in predicting effects at a landscape level. The importance of understanding the spatial structure of a population in uncertainty reduction is addressed.     

Regional Risk Assessment of a Brazilian Rain Forest Reserve

The objective of this study was to identify subareas inside and near an Atlantic Rain Forest reserve, the Parque Estadual Turístico do Alto Ribeira (PETAR), most likely to be affected by land use in the vicinity of the area. In addition, the study aimed to compare risks per stressor source (agriculture, human settlements and mining) to both epigean (surface) and hypogean (subterranean) aquatic fauna. The methodological approach included the relative vulnerability of endpoints to the stressors (pesticides, metals, nutrients, and particles) and ranking of stressor sources and habitats (epigean and hypogean streams) based on their relative distribution in 14 subareas within the catchment areas of the main rivers that cross PETAR: Pilões, Betari and Iporanga. Four subareas presented high risk for both epigean and hypogean fauna. Three of those areas were located inside the Betari catchment area, where most of the settlements and abandoned lead mines are located. The fourth area was situated in the headwaters of the Pilões River, where agricultural activities are intense. Agriculture and human settlements were the activities most likely to cause impacts on aquatic ecosystems. Uses of risk assessment results include management of the PETAR and communication to stakeholders by the Park Administration.