ALBERT

Description: The cotyledon of legume seeds is a storage organ that provides nutrients for seed germination and seedling growth. The spatial and temporal control of the degradation processes within cotyledons has not been elucidated. Calcium oxalate (CaOx) crystals, a common calcium deposit in plants, have often been reported to be present in legume seeds. In this study, micro-computed tomography (micro-CT) was employed at the SPring-8 facility to examine the three-dimensional distribution of crystals inside cotyledons during seed maturation and germination of Lotus miyakojimae (previously Lotus japonicus accession Miyakojima MG-20). Using this technique, we could detect the outline of the embryo, void spaces in seeds and the cotyledon venation pattern. We found several sites that strongly inhibited X-ray transmission within the cotyledons. Light and polarizing microscopy confirmed that these areas corresponded to CaOx crystals. Three-dimensional observations of dry seeds indicated that the CaOx crystals in the L. miyakojimae cotyledons were distributed along lateral veins; however, their distribution was limited to the abaxial side of the procambium. The CaOx crystals appeared at stage II (seed-filling stage) of seed development, and their number increased in dry seeds. The number of crystals in cotyledons was high during germination, suggesting that CaOx crystals are not degraded for their calcium supply. Evidence for the conservation of CaOx crystals in cotyledons during the L. miyakojimae germination process was also supported by the biochemical measurement of oxalic acid levels.

Description: In all eukaryotes, transcribed precursor tRNAs are maturated by processing and modification processes in nucleus and are transported to the cytoplasm. The cytoplasmic export protein (Cex1p) captures mature tRNAs from the nuclear export receptor (Los1p) on the cytoplasmic side of the nuclear pore complex, and it delivers them to eukaryotic elongation factor 1α. This conserved Cex1p function is essential for the quality control of mature tRNAs to ensure accurate translation. However, the structural basis of how Cex1p recognizes tRNAs and shuttles them to the translational apparatus remains unclear. Here, we solved the 2.2 Å resolution crystal structure of Saccharomyces cerevisiae Cex1p with C-terminal 197 disordered residues truncated. Cex1p adopts an elongated architecture, consisting of N-terminal kinase-like and a C-terminal α-helical HEAT repeat domains. Structure-based biochemical analyses suggested that Cex1p binds tRNAs on its inner side, using the positively charged HEAT repeat surface and the C-terminal disordered region. The N-terminal kinase-like domain acts as a scaffold to interact with the Ran-exportin (Los1p·Gsp1p) machinery. These results provide the structural basis of Los1p·Gsp1p·Cex1p·tRNA complex formation, thus clarifying the dynamic mechanism of tRNA shuttling from exportin to the translational apparatus.

Description: This study investigates pressure effects on the magnetic properties of non-interacting single-domain (SD) magnetite. Using a high-pressure cell specially designed for a Magnetic Property Measurement System, magnetic hysteresis measurements were conducted under high pressures of up to 1 GPa on natural plagioclase crystals containing much acicular SD magnetite. Coercivity and saturation magnetization were nearly constant with pressure, while saturation remanent magnetization and coercivity of remanence decreased with pressure at moderate rates of –8 per cent GPa –1 and –18 per cent GPa –1 , respectively. These results suggest that temperature effects govern the magnetic behaviour of acicular SD magnetite grains in the middle and lower crusts.

Description: To investigate the nature and origin of across-arc geochemical variations over time in mantle wedge derived magmas, we have carried out a geochemical study of basalts in the NE Japan arc spanning an age range from 35 Ma to the present. Back-arc basalts erupted at 24–18 Ma, 10–8 Ma, 6–3 Ma and 2·5–0 Ma have higher concentrations of both high field strength elements (HFSE) and rare earth elements (REE) [particularly light REE (LREE) and middle REE (MREE)], and higher incompatible trace element ratios compared with frontal-arc basalts at any given time. Geochemical modeling of Nb/Yb versus Nb shows that the frontal-arc and back-arc compositional differences are independent of subduction modification and can, in many cases, be explained by different degrees of melting (higher degrees of melting for frontal-arc magmas and lower degrees of melting for back-arc magmas) of a nearly homogeneous depleted mid-ocean ridge basalt (MORB) mantle (DMM)-like source, although there are several exceptions. These include some Pliocene frontal-arc basalts that may originate from a source that is slightly more depleted than DMM, several 35–32 Ma and 24–18 Ma back-arc basalts derived from a lithospheric mantle source that is enriched in HFSE compared with DMM, and a rare 16–12 Ma basalt that was erupted in the back-arc but was produced by a similar degree of melting to frontal-arc basalts erupted at the same time. Variations in ratios of fluid-mobile and -immobile elements and those of melt-mobile and -immobile elements for the 35–0 Ma NE Japan basalts indicate that the principal subduction component added to the source mantle prior to generation of these basalt magmas is a sediment-derived melt. Comparison of Sr and Nd isotopic compositions for Pacific Ocean MORB, the NE Japan basalts and subducting sediments suggests that the isotopic compositions of most post-16 Ma more depleted back-arc basalts can be explained by the addition of 〈2% bulk sediment; the most enriched isotope compositions of the subcontinental lithosphere-derived magmas can be accounted for by addition of a maximum 5–7% Japan Trench Sediment (JTS), if the original Sr and Nd compositions of the lithosphere approximated that of DMM. The Sr and Nd isotope composition of the frontal-arc basalts can be accounted for by the addition of 1–5% JTS. A depleted asthenospheric mantle (DMM-like) upwelling model with interaction between asthenospheric mantle-derived magmas and overlying lithospheric mantle can account for the geochemical characteristics of the 35–0 Ma NE Japan basalts. The frontal-arc magmas were generally generated by higher degrees of melting of the shallower part of the asthenospheric mantle, whereas the back-arc magmas resulted from lower degrees of melting of the deeper part of asthenospheric mantle. These latter magmas underwent interaction with the lithospheric mantle, resulting in more enriched Sr and Nd isotopic signatures for the pre-18 Ma back-arc basalts and post-22 Ma frontal-arc basalts, but less interaction, resulting in more depleted Sr and Nd isotopic signatures, for most of the back-arc basalts younger than 16 Ma.

Description: Late Oligocene to Middle Miocene adakitic andesites are found in the southern part of Okushiri Island, the northern Noto Peninsula and in the Toyama region in the present-day back-arc margin of the SW and NE Japan arcs. On Okushiri Island, adakitic andesite is accompanied by moderately alkaline basalt, whereas on the Noto Peninsula, adakitic andesite has been erupted along with high magnesian andesite (HMA), bronzite andesite and tholeiitic basalt. Adakitic andesites from all three locations are characterized by high Sr/Y and low Y, and have higher MgO contents than adakitic melts generated by experimental melting of metabasalt and amphibolite. They also have higher Ni and Cr contents than either Archaean tonalite–trondhjemite–granodiorite (TTG) suites or Early Cretaceous adakitic granites, which have been attributed to partial melting of subducted oceanic crust. The Noto Peninsula adakitic andesite has Sr and Nd isotopic compositions identical to normal mid-ocean ridge basalt (N-MORB), whereas the Okushiri Island and Toyama adakitic andesites are more isotopically primitive than N-MORB. The Noto Peninsula primary adakitic melt was derived from subducted oceanic N-MORB crust, whereas the Okushiri Island and Toyama primary adakites are interpreted as melts of subducted N-MORB and sediment that have subsequently interacted with the overlying mantle wedge peridotite. To explain the comagmatism of adakite, HMA and basalt, the following model is proposed. A hydrated adakitic diapir ascends from the subducting slab and is heated because it enters the overlying hot mantle wedge. The subsequent establishment of thermal and H 2 O gradients in the adakitic diapir and surrounding mantle wedge peridotite results in concurrent generation of adakitic andesite magma in the inner adakitic diapir region (low temperature and high H 2 O content), HMA and bronzite andesite magmas in the intermediate peridotite region (intermediate temperature and H 2 O content), and tholeiitic basalt magma in the outer peridotite region (high temperature and lower H 2 O content). Comagmatic adakite and mildly alkaline basalt are found in cooler and wetter adakitic diapirs and hotter and drier peridotite regions respectively. The most likely tectono-magmatic situation for the genesis of adakitic magmas in this example of a cool subduction zone involves upwelling of hot asthenosphere into the subcontinental lithosphere beneath the back-arc side of the NE Japan arc and northern end of the SW Japan arc, during the period spanning the pre-Japan Sea opening to syn-opening stages. The unusually high temperature conditions established in the mantle wedge owing to upwelling of hot asthenosphere caused partial melting of the relatively cool subducting Pacific plate, resulting in the generation of adakitic magmas.

Description: Glycogen phosphorylase (GP) exists in two interconvertible forms, GPa (phosphorylated form, high activity) and GPb (nonphosphorylated form, low activity). Phosphorylase kinase (PhK) catalyses the phosphorylation of GPb and plays a key role in the cascade system for regulating glycogen metabolism. In this study, we developed a highly sensitive and nonradioactive assay for PhK activity by measuring the enhanced GP activity towards a pyridylaminated maltohexaose. The enhanced GP activity ( A ) was calculated by the following formula: A = A + – A 0 , where A + and A 0 represent the GP activities of the PhK-treated and PhK-nontreated samples, respectively. Using a high-performance liquid chromatograph equipped with a fluorescence spectrophotometer, the product of GP activity could be isolated and quantified at 10 fmol. This method does not require the use of any radioactive compounds and only 1 µg of GPb per sample was needed to obtain A + and A 0 values. The remarkable reduction in GPb concentration enabled us to discuss an interesting new role for glycogen in PhK activity.

Description: We have investigated basic properties of transition remanent magnetization of natural magnetite in granite samples collected from the Minnesota River Valley, North America. Transition remanence was imparted during cooling and/or warming through the Verwey transition around 120 K. Depending on magnetic field conditions during cooling and warming, three types of transition remanences have been categorized: (1) TrRM, acquired during a cycle of field cooling and field warming; (2) TrWRM, acquired during zero-field cooling and field warming and (3) TrCRM, imparted during field cooling and zero-field warming. These remanences fulfil basic laws of remanent magnetization: (1) directions of the transition remanences are parallel to direction of the applied field (the law of parallelism), (2) intensities of the transition remanences are proportional to the applied field intensity (the law of proportionality) and (3) sum of the partial transition remanences is equal to the total transitional remanence, that is, TrRM = TrWRM + TrCRM. In addition, the ratio of TrRM to TRM LTD (the demagnetized component of thermoremanent magnetization by low-temperature demagnetization) shows a nearly constant value of ~0.34. This relationship might reflect differences in equilibrium magnetic domain state at low and high temperature.

Description: The Ryozen Formation, which crops out on the trench side of the NE Japan arc, contains middle Miocene rhyodacite with adakite-like trace element geochemical characteristics (Ryozen adakitic rhyodacite) and spatially and temporally related basalt (Ryozen basalt) and andesite (Ryozen andesite). K–Ar age data for the basalt and a zircon U–Pb age for the adakitic rhyodacite, combined with the stratigraphy, suggest that all of these volcanic rocks were erupted at about 16–14 Ma. The primitive nature of the Ryozen basalt is shown by its high MgO (maximum 14·1 wt %), Ni (392 ppm) and Cr (1193 ppm) contents. Using the olivine maximum fractionation model, the segregation depth of the parental primary magma to this basalt is estimated at c . 50 km (about 1·5 GPa). The Ryozen andesite has slightly higher 87 Sr/ 86 Sr initial (SrI) and lower 143 Nd/ 144 Nd initial (NdI) ratios than the Ryozen basalt. This, and the characteristics of the variation trends defined by basalt and andesite samples in SiO 2 versus major and trace element variation diagrams, suggests that the andesite may have resulted from fractional crystallization of basaltic magma with minor assimilation of pre-Cretaceous sedimentary rocks (i.e. an AFC process). The Ryozen rhyodacite has phenocrysts of plagioclase, amphibole, garnet and titanomagnetite, and is characterized by low Sr/Y ratios (~30), low Y concentrations (〈10 ppm), high chondrite-normalized La/Yb [(La/Yb) cn ] (〉25) and low chondrite-normalized Yb [(Yb) cn ] values (〈5 ppm). These geochemical characteristics are similar to those of a new adakite subgroup (rhyodacite lavas in eastern Jamaica; Jamaican-type adakite). Thus, we define the Ryozen rhyodacite as the Ryozen low Sr/Y adakitic rhyodacite. A potential mechanism for the generation of this rhyodacite is crystal fractionation of plagioclase, orthopyroxene, clinopyroxene, amphibole, garnet, titanomagnetite and minor apatite from an andesitic parent magma. This mechanism is consistent with mass-balance modeling, which matches the observed major and trace element chemistry, as well as SrI and NdI, for the Ryozen andesite and low Sr/Y adakitic rhyodacite. The most likely tectono-magmatic model for the production of the volcanic rocks of the Ryozen Formation involves the upwelling of depleted hot asthenosphere, which modified the thermal structure of the mantle wedge beneath the trench side of the arc during the middle Miocene. This resulted in partial melting of both mantle wedge peridotite and the relatively cool subducting Pacific plate, leading to the simultaneous production of primitive basalt, normal andesite, high-magnesium andesite and low and high Sr/Y adakitic rhyodacites.

Description: In this study, we investigated the distribution of small photosynthetic eukaryotes in the near-surface layer of the western North Pacific at four stations, including two oceanic stations where the subarctic Oyashio and subtropical Kuroshio currents influence a transition region and the bay mouth and head of the Sendai Bay, from April 2012 to May 2013. Flow cytometry was applied to sort small photosynthetic eukaryotes (〈5 μm), and high-throughput sequencing of 18S rDNA was performed. Our taxonomic analysis showed that 19/195 operational taxonomic units (OTUs) were frequently distributed among all sites. Composition analysis showed that the OTUs had characteristic patterns and were divided into four main groups. Two groups reflected the low-saline water and winter season, with the characteristic OTUs belonging to diatoms; Chaetoceros and Leptocylindrus were characteristic of low saline water, and two diatom genera ( Minidiscus and Minutocellus ) and Cryptomonadales-related OTUs were prevalent in the winter. Our results indicate that the community composition of small photosynthetic eukaryotes seasonally changes in a dynamic manner according to variations in water properties.

Description: Escherichia coli lyses by lambda phage propagation. Circular plasmid DNA was present during E. coli lysis as an extracellular plasmid DNA (excpDNA) that was stable enough to transform coexisting competent Bacillus subtilis cells. Detailed investigations unveiled that excpDNA is transient in both quality and quantity, with stability lasting no more than several hours. A survey using E. coli lambda lysogens with various genetic backgrounds demonstrated that the loss of Endonuclease I ( endA :: kan ) conferred extraordinary stability upon excpDNA for as long as 48 h. Studies on endA mutants suggested that excpDNA remained localized in cell debris, in contrast to E. coli genome DNA, which diffused into medium at an early point in lysis. Lambda lysogens constructed on endA recA mutants are presented for potential pipelines in delivery to other competent proficient microbes.