Significant transcriptional changes in mature daughter Varroa destructor mites during infestation of different developmental stages of honeybees

Background: Varroa destructor is considered a major cause of honeybee (Apis mellifera) colony losses worldwide. Although V. destructor mites exhibit preference behavior for certain honeybee lifecycle stages, the mechanism underlying host finding and preference remains largely unknown. Results: By using a de novo transcriptome assembly strategy, we sequenced the mature daughter V. destructor mite transcriptome during infestation of different stages of honeybees (brood cells, newly emerged bees and adult bees). A total of 132 779 unigenes were obtained with an average length of 2745 bp and N50 of 5706 bp. About 63.1% of the transcriptome could be annotated based on sequence homology to the predatory mite Metaseiulus occidentalis proteins. Expression analysis revealed that mature daughter mites had distinct transcriptome profiles after infestation of different honeybee stages, and that the majority of the differentially expressed genes (DEGs) of mite infesting adult honeybees were down-regulated compared to that infesting the sealed brood cells. Gene ontology and KEGG pathway enrichment analyses showed that a large number of DEGs were involved in cellular process and metabolic process, suggesting that Varroa mites undergo metabolic adjustment to accommodate the cellular, molecular and/or immune response of the honeybees. Interestingly, in adult honeybees, some mite DEGs involved in neurotransmitter biosynthesis and transport were identified and their levels of expression were validated by quantitative polymerase chain reaction (qPCR). Conclusion: These results provide evidence for transcriptional reprogramming in mature daughter Varroa mites during infestation of honeybees, which may be relevant to understanding the mechanism underpinning adaptation and preference behavior of these mites for honeybees. © 2020 Society of Chemical Industry

An Indirect Simulation-Optimization Model for Determining Optimal TMDL Allocation under Uncertainty

An indirect simulation-optimization model framework with enhanced computational efficiency and risk-based decision-making capability was developed to determine optimal total maximum daily load (TMDL) allocation under uncertainty. To convert the traditional direct simulation-optimization model into our indirect equivalent model framework, we proposed a two-step strategy: (1) application of interval regression equations derived by a Bayesian recursive regression tree (BRRT v2) algorithm, which approximates the original hydrodynamic and water-quality simulation models and accurately quantifies the inherent nonlinear relationship between nutrient load reductions and the credible interval of algal biomass with a given confidence interval; and (2) incorporation of the calibrated interval regression equations into an uncertain optimization framework, which is further converted to our indirect equivalent framework by the enhanced-interval linear programming (EILP) method and provides approximate-optimal solutions at various risk levels. The proposed strategy was applied to the Swift Creek Reservoir’s nutrient TMDL allocation (Chesterfield County, VA) to identify the minimum nutrient load allocations required from eight sub-watersheds to ensure compliance with user-specified chlorophyll criteria. Our results indicated that the BRRT-EILP model could identify critical sub-watersheds faster than the traditional one and requires lower reduction of nutrient loadings compared to traditional stochastic simulation and trial-and-error (TAE) approaches. This suggests that our proposed framework performs better in optimal TMDL development compared to the traditional simulation-optimization models and provides extreme and non-extreme tradeoff analysis under uncertainty for risk-based decision making

Carbon dioxide concentration can limit the identification of C-4 plants by stable isotope composition

The global expansion of C-4 plants during the Late Cenozoic is an important event in the Earth's environmental-ecosystem evolution. Taking into account the nonglobal expansion of C-4 plants, the CO2 concentration is not the only prerequisite for C-4 expansion. The direct driving factors for C-4 expansion may be associated with regional arid and/or warm seasonal precipitation and temperature variations. However, a large change in the CO2 concentration occurred, varying from 100 similar to 300 to > 2000 ppm during geological history; thus, it is necessary to understand the impact of such changes in the atmospheric CO2 concentration on the delta C-13 values of C-3 and C-4 plants during different geological periods. In this article, we analyzed the delta C-13 values for seven C-4 and C-3 plants grown under different CO2 concentrations for 10, 20, and 30 days. According to our study, the delta C-13 records for all the C-3 and C-4 plants show a rapid decrease followed by a slowly stable decreased trend with increasing CO2 concentration when the plants were grown for 10, 20, and 30 days. Comparing with the value averaging about -26 to -27 parts per thousand for C-3 plants and about -12 parts per thousand for C-4 plants, when the CO2 levels reach 20,000 ppm, all of the delta C-13 values of C-4 plants become more negative, varying from -27.5 to -36.1 parts per thousand, which fall into the range of delta C-13 values for C-3 plants. Namely, the increase of carbon dioxide can limit the identification of C-4 plants by carbon isotope composition. Thus, the expansion of C-4 plants as reconstructed from the geological records of carbon isotopes possibly does not reflect the origin and expansion of C-4 plants when atmospheric CO2 concentration was reduced to a threshold value, as previously thought. However, another possible explanation is that the atmospheric CO2 concentration was reduced to a threshold value from which the carbon isotope values of C-3 and C-4 plants can be distinguished. Therefore, we suggest that it is necessary to understand the delta C-13 range for C-3 and C-4 plants, to accurately evaluate the origin and expansion of C-4 plants, for geological periods when a high CO2 concentration occurred

Review of the East Palaearctic and North Oriental Psyttalia Walker, with the description of three new species (Hymenoptera, Braconidae, Opiinae)

Volume: 629Start Page: 103End Page: 15