Effect of floods on the δ13C values in plant leaves: a study of willows in Northeastern Siberia

Although stable carbon isotopic composition (δ13C) of plants has been widely used to indicate different water regimes in terrestrial ecosystems over the past four decades, the changes in the plant δ13C value under waterlogging have not been sufficiently clarified. With the enhanced global warming in recent years, the increasing frequency and severity of river floods in Arctic regions lead to more waterlogging on willows that are widely distributed in river lowland. To investigate the δ13C changes in plants under different water conditions (including waterlogging), we measured the δ13C values in the leaves of willows with three species, Salix boganidensis, S. glauca, and S. pulchra, and also monitored changes in plant physiology, under several major flooding conditions in Northeastern Siberia. The foliar δ13C values of willows varied, ranging from −31.6 to −25.7‰ under the different hydrological status, which can be explained by: (i) under normal conditions, the foliar δ13C values decrease from dry (far from a river) to wet (along a river bank) areas; (ii) the δ13C values increase in frequently waterlogged areas owing to stomatal closure; and (iii) after prolonged flooding periods, the δ13C values again decrease, probably owing to the effects of not only the closure of stomata but also the reduction of foliar photosynthetic ability under long period of waterlogging. Based on these results, we predict that plant δ13C values are strongly influenced by plant physiological responses to diverse hydrological conditions, particularly the long periods of flooding, as occurs in Arctic regions

Cytochromec−Crown Ether Complexes as Supramolecular Catalysts: Cold-Active Synzymes for Asymmetric Sulfoxide Oxidation in Methanol

A series of supramolecular complexes of various cytochrome c proteins with 18-crown-6 derivatives behave as cold-active synzymes in the H_2O_2 oxidation of racemic sulfoxides. This interesting behavior contrasts with native functionality, where the employed proteins act as electron transfer carriers. ESI-MS, UV, CD, and Raman spectroscopic characterizations reveal that four or five 18-crown-6 molecules strongly bind to the surface of the cytochrome c and also that nonnatural low-spin hexacoordinate heme structures are induced in methanol. Significantly, crown ether complexation can convert catalytically inactive biological forms to catalytically active artificial forms. Horse heart, pigeon breast, and yeast cytochromes c all stereoselectively oxidize (S)-isomers of methyl tolyl sulfoxide and related sulfoxides upon crown ether complexation. These supramolecular catalysts show the highest efficiency and enantiomer selectivity at −40 °C in the H_2O_2-dependent sulfoxide oxidation, while oxidative decomposition of the heme moieties predominantly occurs at room temperature. The oxidation reactivity of the employed sulfoxides is apparently related to steric constraints and electrochemical oxidation potentials of their S O bonds. Among the cytochrome c complexes, yeast cytochrome c demonstrates the lowest catalytic activity and degradation reactivity. It has a significantly different protein sequence, suggesting that crown ether complexation effectively activates heme coordination but may additionally alter the native backbone structure. The proper combination of cytochrome c proteins, 18-crown-6 receptors, and external circumstances can be used to successfully generate “protein-based supramolecular catalysts” exhibiting nonbiological reactivities

Inter-annual variation in CH4 efflux and the associated processes with reference to delta-13C-, delta-D-CH4 at the Lowland of Indigirka River in Northeastern Siberia

第6回極域科学シンポジウム分野横断セッション：[IA] 急変する北極気候システム及びその全球的な影響の総合的解明―GRENE北極気候変動研究事業研究成果報告2015―11月19日（木）　国立極地研究所１階交流アトリウ

Regional and interannual variation of snow cover and melting at the GRENE Arctic observation sites - Analysis of forest, tundra, glacier area, river area in Siberia -

第3回極域科学シンポジウム/特別セッション「これからの北極研究」11月28日（水） 国立極地研究所 2階大会議

Methane Oxidation Potential of Arctic Wetland Soil of a Taiga-Tundra Ecotone in Northeastern Siberia

第6回極域科学シンポジウム分野横断セッション：[IA] 急変する北極気候システム及びその全球的な影響の総合的解明―GRENE北極気候変動研究事業研究成果報告2015―11月19日（木）　国立極地研究所１階交流アトリウ

Arctic challenge - our research strategy for Arctic climate change

第3回極域科学シンポジウム/特別セッション「これからの北極研究」11月28日（水） 国立極地研究所 2階大会議

The brain-derived neurotrophic factor Val66Met polymorphism increases segregation of structural correlation networks in healthy adult brains

Background Although structural correlation network (SCN) analysis is an approach to evaluate brain networks, the neurobiological interpretation of SCNs is still problematic. Brain-derived neurotrophic factor (BDNF) is well-established as a representative protein related to neuronal differentiation, maturation, and survival. Since a valine-to-methionine substitution at codon 66 of the BDNF gene (BDNF Val66Met single nucleotide polymorphism (SNP)) is well-known to have effects on brain structure and function, we hypothesized that SCNs are affected by the BDNF Val66Met SNP. To gain insight into SCN analysis, we investigated potential differences between BDNF valine (Val) homozygotes and methionine (Met) carriers in the organization of their SCNs derived from inter-regional cortical thickness correlations. / Methods Forty-nine healthy adult subjects (mean age = 41.1 years old) were divided into two groups according to their genotype (n: Val homozygotes = 16, Met carriers = 33). We obtained regional cortical thickness from their brain T1 weighted images. Based on the inter-regional cortical thickness correlations, we generated SCNs and used graph theoretical measures to assess differences between the two groups in terms of network integration, segregation, and modularity. / Results The average local efficiency, a measure of network segregation, of BDNF Met carriers’ network was significantly higher than that of the Val homozygotes’ (permutation p-value = 0.002). Average shortest path lengths (a measure of integration), average local clustering coefficient (another measure of network segregation), small-worldness (a balance between integration and segregation), and modularity (a representative measure for modular architecture) were not significantly different between group (permutation p-values ≧ 0.01). / Discussion and Conclusion Our results suggest that the BDNF Val66Met polymorphism may potentially influence the pattern of brain regional morphometric (cortical thickness) correlations. Comparing networks derived from inter-regional cortical thickness correlations, Met carrier SCNs have denser connections with neighbors and are more distant from random networks than Val homozygote networks. Thus, it may be necessary to consider potential effects of BDNF gene mutations in SCN analyses. This is the first study to demonstrate a difference between Val homozygotes and Met carriers in brain SCNs

A spatio-temporal pattern of past tree response to climate changes deduced from tree-ring width, delta-13C and a DGVM over the pan-Arctic ecosystems

第6回極域科学シンポジウム分野横断セッション：[IA] 急変する北極気候システム及びその全球的な影響の総合的解明―GRENE北極気候変動研究事業研究成果報告2015―11月19日（木）　国立極地研究所 2階 大会議

Current status of pan-Arctic terrestrial ecosystem and its possible changes

第6回極域科学シンポジウム特別セッション：[S] 北極温暖化とその影響 ―GRENE 北極気候変動プロジェクトと新しい方向性―11月18日（水）　国立極地研究所 2階 大会議