Sensory evaluation of character impact components in an apple model mixture

Food aromas generally are complex mixtures of volatiles. In the present study, we investigated the joint effects of hexyl acetate, trans-2-hexenal and 1-hexanol on the multi-attribute perception of an apple aroma. The first two substances were identified earlier as positive contributors to the apple aroma (high character impact), whereas the third component was identified as an irrelevant or negative contributor (low character impact). Aroma quality was quantified using a set of eight graphic rating scales. All three components had significant effects on the aroma profiles. These effects consist mainly of an effect of each component on the attribute that described its individual character and an effect of all three components on ratings on the main character attribute 'apple'. As expected, the high impact components increased 'apple' ratings, whereas the low character impact component decreased 'apple' ratings. Furthermore, intensity ratings on the attribute that corresponded with the odour of the low impact component were suppressed by the presence of high impact components. These results indicate that the contributions of odorants to the mixture's aroma are not linear combinations of separate odour intensities, because sensory interactions were observed. In addition, humans detect components in complex mixtures more accurately than studies on identification performance have suggested. We conclude that for an adequate assessment of the effects of multiple mixture components on changes in aroma perception, it is sufficient to employ multiple response scales measuring intensities of attributes that are distinctive with respect to the expected qualitative changes. Results of this approach should be subjected to multivariate methods of statistical analysis.     

Binding to serine 65‐phosphorylated ubiquitin primes Parkin for optimal PINK1‐dependent phosphorylation and activation

Mutations in the mitochondrial protein kinase PINK1 are associated with autosomal recessive Parkinson disease (PD). We and other groups have reported that PINK1 activates Parkin E3 ligase activity both directly via phosphorylation of Parkin serine 65 (Ser⁶⁵)—which lies within its ubiquitin‐like domain (Ubl)—and indirectly through phosphorylation of ubiquitin at Ser⁶⁵. How Ser⁶⁵‐phosphorylated ubiquitin (ubiquitin^{Phospho‐Ser65}) contributes to Parkin activation is currently unknown. Here, we demonstrate that ubiquitin^{Phospho‐Ser65} binding to Parkin dramatically increases the rate and stoichiometry of Parkin phosphorylation at Ser⁶⁵ by PINK1 in vitro. Analysis of the Parkin structure, corroborated by site‐directed mutagenesis, shows that the conserved His302 and Lys151 residues play a critical role in binding of ubiquitin^{Phospho‐Ser65}, thereby promoting Parkin Ser⁶⁵ phosphorylation and activation of its E3 ligase activity in vitro. Mutation of His302 markedly inhibits Parkin Ser⁶⁵ phosphorylation at the mitochondria, which is associated with a marked reduction in its E3 ligase activity following mitochondrial depolarisation. We show that the binding of ubiquitin^{Phospho‐Ser65} to Parkin disrupts the interaction between the Ubl domain and C‐terminal region, thereby increasing the accessibility of Parkin Ser⁶⁵. Finally, purified Parkin maximally phosphorylated at Ser⁶⁵ in vitro cannot be further activated by the addition of ubiquitin^{Phospho‐Ser65}. Our results thus suggest that a major role of ubiquitin^{Phospho‐Ser65} is to promote PINK1‐mediated phosphorylation of Parkin at Ser⁶⁵, leading to maximal activation of Parkin E3 ligase activity. His302 and Lys151 are likely to line a phospho‐Ser⁶⁵‐binding pocket on the surface of Parkin that is critical for the ubiquitin^{Phospho‐Ser65} interaction. This study provides new mechanistic insights into Parkin activation by ubiquitin^{Phospho‐Ser65}, which could aid in the development of Parkin activators that mimic the effect of ubiquitin^{Phospho‐Ser65}.     

Hemlock Declines Rapidly with Hemlock Woolly Adelgid Infestation: Impacts on the Carbon Cycle of Southern Appalachian Forests

The recent infestation of southern Appalachian eastern hemlock stands by hemlock woolly adelgid (HWA) is expected to have dramatic and lasting effects on forest structure and function. We studied the short-term changes to the carbon cycle in a mixed stand of hemlock and hardwoods, where hemlock was declining due to either girdling or HWA infestation. We expected that hemlock would decline more rapidly from girdling than from HWA infestation. Unexpectedly, in response to both girdling and HWA infestation, hemlock basal area increment (BAI) reduced substantially compared to reference hardwoods in 3 years. This decline was concurrent with moderate increases in the BAI of co-occurring hardwoods. Although the girdling treatment resulted in an initial pulse of hemlock needle inputs, cumulative litter inputs and O horizon mass did not differ between treatments over the study period. Following girdling and HWA infestation, very fine root biomass declined by 20–40% in 2 years, which suggests hemlock root mortality in the girdling treatment, and a reduction in hemlock root production in the HWA treatment. Soil CO₂ efflux (E _soil) declined by approximately 20% in 1 year after both girdling and HWA infestation, even after accounting for the intra-annual variability of soil temperature and moisture. The reduction in E _soil and the concurrent declines in BAI and standing very fine root biomass suggest rapid declines in hemlock productivity from HWA infestation. The accelerated inputs of detritus resulting from hemlock mortality are likely to influence carbon and nutrient fluxes, and dictate future patterns of species regeneration in these forest ecosystems. AEN performed research and analyzed data; NW performed research, analyzed data, and wrote the article; CRF contributed new methods, analyzed data, and wrote the article; RLH designed the study; JMV conceived of and designed the study; and BDK performed research.     

Fine root length production,mortality and standing root crop dynamics in an intensively managed sweetgum (Liquidambar styraciflua L.) coppice

We used minirhizotrons and micro-video technology to study fine root production, mortality and standing root crop dynamics in an intensively managed sweetgum (Liquidambar styraciflua L.) coppice. The experiment was a split-plot design with two levels of fertilization. Low-level treatment plots received 560 kg ha-1 yr-1 fertilizer (19:9:19 NPK) via a drip irrigation system and high-level treatment plots received twice this amount. Approximately 150 cm yr-1 irrigation was applied to all treatments. There were no significant treatment differences in daily average fine root production or mortality. The phenology of fine root production and mortality, however, was characterized by strongly seasonal asynchrony. Production increased throughout the summer, peaked in September and declined sharply over the winter. Root mortality was not observed in either treatment until August, and then increased significantly throughout the winter months. There were also no significant treatment differences in standing fine root length. Standing live root length was greatest in the fall and dead root length was greatest over the winter. Roots in the upper 25 cm of the soil profile appeared to be significantly more dynamic (i.e. greater production and mortality) than deeper roots in both treatments. High levels of fertilization apparently do not alter fine root dynamics at our sites, in contrast to fertilization responses observed in other, more nutrient-poor environments.     

DNA methylation pattern of CALCA in preterm neonates with bacterial sepsis as a putative epigenetic biomarker

Diagnosis of bacterial sepsis in preterm neonates can be difficult when using serum markers that rely on physiological changes because these changes may not necessarily be the result of bacterial infections alone. This retrospective investigation explores the potential use of the DNA methylation pattern of CpG sites in the promoter region of the calcitonin-related polypeptide α (CALCA) gene as an epigenetic biomarker for bacterial sepsis in preterm newborns. Four novel changes in the DNA methylation of eight CpG sites were detected in this gene and are present only in neonates with bacterial sepsis: (1) partial methylation at -769 CpG in gram-negative or gram-positive early onset sepsis (EOS) and late onset sepsis (LOS) episodes; (2) demethylation of 8 CpGs in gram-negative EOS followed by LOS (ELS) and in gram-negative EOS; (3) demethylation of 7 CpGs in gram-positive ELS and gram-positive EOS; (4) -771 C:G > T:A; 5′ de novo -778 CpG mutation on both alleles in EOS. These changes were not detected in birth weight and gestational age matched controls or in newborns with isolated infections. Our results indicate that the DNA methylation pattern of the promoter region of the CALCA gene varies in different types of bacterial preterm sepsis, thus suggesting a potential use as an epigenetic biomarker. A prospective confirmation of these results is essential.     

Comparative Genomic Analysis of Mannheimia haemolytica from Bovine Sources

Bovine respiratory disease is a common health problem in beef production. The primary bacterial agent involved, Mannheimia haemolytica, is a target for antimicrobial therapy and at risk for associated antimicrobial resistance development. The role of M. haemolytica in pathogenesis is linked to serotype with serotypes 1 (S1) and 6 (S6) isolated from pneumonic lesions and serotype 2 (S2) found in the upper respiratory tract of healthy animals. Here, we sequenced the genomes of 11 strains of M. haemolytica, representing all three serotypes and performed comparative genomics analysis to identify genetic features that may contribute to pathogenesis. Possible virulence associated genes were identified within 14 distinct prophage, including a periplasmic chaperone, a lipoprotein, peptidoglycan glycosyltransferase and a stress response protein. Prophage content ranged from 2–8 per genome, but was higher in S1 and S6 strains. A type I-C CRISPR-Cas system was identified in each strain with spacer diversity and organization conserved among serotypes. The majority of spacers occur in S1 and S6 strains and originate from phage suggesting that serotypes 1 and 6 may be more resistant to phage predation. However, two spacers complementary to the host chromosome targeting a UDP-N-acetylglucosamine 2-epimerase and a glycosyl transferases group 1 gene are present in S1 and S6 strains only indicating these serotypes may employ CRISPR-Cas to regulate gene expression to avoid host immune responses or enhance adhesion during infection. Integrative conjugative elements are present in nine of the eleven genomes. Three of these harbor extensive multi-drug resistance cassettes encoding resistance against the majority of drugs used to combat infection in beef cattle, including macrolides and tetracyclines used in human medicine. The findings here identify key features that are likely contributing to serotype related pathogenesis and specific targets for vaccine design intended to reduce the dependency on antibiotics to treat respiratory infection in cattle.     

Phenotypic and genetic differentiation among yellow monkeyflower populations from thermal and non-thermal soils in Yellowstone National Park

In flowering plants, soil heterogeneity can generate divergent natural selection over fine spatial scales, and thus promote local adaptation in the absence of geographic barriers to gene flow. Here, we investigate phenotypic and genetic differentiation in one of the few flowering plants that thrives in both geothermal and non-thermal soils in Yellowstone National Park (YNP). Yellow monkeyflowers (Mimulus guttatus) growing at two geothermal ("thermal") sites in YNP were distinct in growth form and phenology from paired populations growing nearby (<500?m distant) in non-thermal soils. In simulated thermal and non-thermal environments, thermal plants remained significantly divergent from non-thermal plants in vegetative, floral, mating system, and phenological traits. Plants from both thermal populations flowered closer to the ground, allocated relatively more to sexual reproduction, were more likely to initiate flowering under short daylengths, and made smaller flowers that could efficiently self-fertilize without pollinators. These shared differences are consistent with local adaptation to life in the ephemeral window for growth and reproduction created by winter and spring snowmelt on hot soils. In contrast, habitat type (thermal vs. non-thermal) explained little of the genetic variation at neutral markers. Instead, we found that one thermal population (Agrostis Headquarters; AHQ-T) was strongly differentiated from all other populations (all F (ST)?>?0.34), which were only weakly differentiated from each other (all F (ST)?相似文献