Monoterpene Variation Mediated Attack Preference Evolution of the Bark Beetle Dendroctonus valens

Several studies suggest that some bark beetle like to attack large trees. The invasive red turpentine beetle (RTB), Dendroctonus valens LeConte, one of the most destructive forest pests in China, is known to exhibit this behavior. Our previous study demonstrated that RTBs preferred to attack large-diameter trees (diameter at breast height, DBH ≥30 cm) over small-diameter trees (DBH ≤10 cm) in the field. In the current study, we studied the attacking behavior and the underlying mechanisms in the laboratory. Behavioral assays showed that RTBs preferred the bark of large-DBH trees and had a higher attack rate on the bolts of these trees. Y-tube assays showed that RTBs preferred the volatiles released by large-DBH trees to those released by small-DBH trees. Subsequent analysis revealed that both large- and small-DBH trees had the same composition of monoterpenes, but the concentration of each component differed; thus it appeared that the concentrations acted as cues for RTBs to locate the right-sized host which was confirmed by further behavioral assays. Moreover, large-DBH pine trees provided more spacious habitat and contained more nutrients, such as nitrogen, than did small-DBH pine trees, which benefited RTBs' fecundity and larval development. RTBs seem to have evolved mechanisms to locate those large hosts that will allow them to maximize their fitness. Monoterpene variation mediated attack preference implies the potential for the management of RTB

Characterization of a putative NsrR homologue in Streptomyces venezuelae reveals a new member of the Rrf2 superfamily

Members of the Rrf2 superfamily of transcription factors are widespread in bacteria but their functions are largely unexplored. The few that have been characterized in detail sense nitric oxide (NsrR), iron limitation (RirA), cysteine availability (CymR) and the iron sulfur (Fe-S) cluster status of the cell (IscR). In this study we combined ChIP-seq with in vitro biochemistry to characterize a putative NsrR homologue in the model organism Streptomyces venezuelae. ChIP seq analysis revealed that rather than regulating the nitrosative stress response like NsrR, Sven6563 binds to a different, much larger regulon of genes with a diverse range of functions, including a range of regulators, genes required for glutamine synthesis, NADH/NAD(P)H metabolism, as well as general DNA/RNA and amino acid/protein turn over. Our biochemical experiments further show that Sven6563 has a [2Fe-2S] cluster and that the switch between oxidized and reduced cluster controls its DNA binding activity in vitro. To our knowledge, both the sensing domain and the target gene regulon are novel for an Rrf2 protein, suggesting Sven6563 represents a new member of the Rrf2 superfamily. Given the redox sensitivity of its Fe-S cluster we have tentatively named the protein RsrR for Redox sensitive response Regulator

Beetroot supplementation improves the physiological responses to incline walking

The final publication is available at Springer via http://dx.doi.org/10.1007/s00421-018-3843-xPurpose: We investigated the effects of an acute 24-h nitrate-rich beetroot juice supplement (BR) on the energy cost, exercise efficiency and blood pressure responses to intermittent walking at different gradients. Methods: In a double-blind, cross-over design, eight participants were provided with a total of 350 ml of nitrate-rich (~20.5 mmol nitrate) BR or placebo (PLA) across 24-h before completing intermittent walking at 3 km/h on treadmill at gradients of 1%, 5%, 10%, 15% and 20%. Results: Resting mean arterial pressure (MAP) was ~4.1% lower after BR (93 vs. 89 mmHg; P = 0.001), as well as during exercise (102 vs. 99 mmHg; P = 0.011) and recovery (97 vs. 94 mmHg; P = 0.001). Exercising (1227 vs. 1129 ml/min P < 0.001) and end-stage (1404 vs. 1249 ml/min; P = 0.002) oxygen uptake (O2) was lower in BR compared to PLA, which was accompanied by an average reduction in phase II ̇O2 amplitude (1067 vs. 940 ml/min; P = 0.025). Similarly, recovery O2 (509 vs. 458 ml/min; P = 0.001) was lower in BR. Whole-blood potassium concentration increased from pre-post exercise in PLA (4.1 ± 0.3 vs. 4.5 ± 0.3 mmol/L; P = 0.013) but not BR (4.1 ± 0.31 vs. 4.3 ± 0.2 mmol/L; P = 0.188). Conclusions: Energy cost of exercise, recovery of O2, MAP and blood markers were ameliorated after BR. Previously reported mechanisms explain these findings, which are more noticeable during less efficient walking at steep gradients (15-20%). These findings have practical implications for hill-walkers