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Abstract Arctic (E22G) mutation in amyloid-β (Aβ enhances Aβ40 fibril accumulation in Alzheimer’s disease (AD). Unlike sporadic AD, familial AD (FAD) patients with the mutation exhibit more Aβ40 in the plaque core. However, structural details of E22G Aβ40 fibrils remain elusive, hindering therapeutic progress. Here, we determine a distinctive W-shaped parallel β-sheet structure through co-analysis by cryo-electron microscopy (cryoEM) and solid-state nuclear magnetic resonance (SSNMR) of in-vitro-prepared E22G Aβ40 fibrils. The E22G Aβ40 fibrils displays typical amyloid features in cotton-wool plaques in the FAD, such as low thioflavin-T fluorescence and a less compact unbundled morphology. Furthermore, kinetic and MD studies reveal previously unidentified in-vitro evidence that E22G Aβ40, rather than Aβ42, may trigger Aβ misfolding in the FAD, and prompt subsequent misfolding of wild-type (WT) Aβ40/Aβ42 via cross-seeding. The results provide insight into how the Arctic mutation promotes AD via Aβ40 accumulation and cross-propagation.

Abstract The molecular system regulating cellular mechanical properties remains unexplored at single-cell resolution mainly due to a limited ability to combine mechanophenotyping with unbiased transcriptional screening. Here, we describe an electroporation-based lipid-bilayer assay for cell surface tension and transcriptomics (ELASTomics), a method in which oligonucleotide-labelled macromolecules are imported into cells via nanopore electroporation to assess the mechanical state of the cell surface and are enumerated by sequencing. ELASTomics can be readily integrated with existing single-cell sequencing approaches and enables the joint study of cell surface mechanics and underlying transcriptional regulation at an unprecedented resolution. We validate ELASTomics via analysis of cancer cell lines from various malignancies and show that the method can accurately identify cell types and assess cell surface tension. ELASTomics enables exploration of the relationships between cell surface tension, surface proteins, and transcripts along cell lineages differentiating from the haematopoietic progenitor cells of mice. We study the surface mechanics of cellular senescence and demonstrate that RRAD regulates cell surface tension in senescent TIG-1 cells. ELASTomics provides a unique opportunity to profile the mechanical and molecular phenotypes of single cells and can dissect the interplay among these in a range of biological contexts.

Abstract Serine metabolism is involved in various biological processes. Here we investigate primary functions of the phosphorylated pathway of serine biosynthesis in a non-vascular plant Marchantia polymorpha by analyzing knockout mutants of MpPGDH encoding 3-phosphoglycerate dehydrogenase in this pathway. Growth phenotypes indicate that serine from the phosphorylated pathway in the dark is crucial for thallus growth. Sperm development requires serine from the phosphorylated pathway, while egg formation does not. Functional MpPGDH in the maternal genome is necessary for embryo and sporophyte development. Under high CO2 where the glycolate pathway of serine biosynthesis is inhibited, suppressed thallus growth of the mutants is not fully recovered by exogenously-supplemented serine, suggesting the importance of serine homeostasis involving the phosphorylated and glycolate pathways. Metabolomic phenotypes indicate that the phosphorylated pathway mainly influences the tricarboxylic acid cycle, the amino acid and nucleotide metabolism, and lipid metabolism. These results indicate the importance of the phosphorylated pathway of serine biosynthesis in the dark, in the development of sperm, embryo, and sporophyte, and metabolism in M. polymorpha.

Ammonium is an important nitrogen source for plants but excess ammonium impairs growth. Here the authors show that ammonium toxicity results from assimilation by GLUTAMINE SYNTHETASE 2 in the plastids which results in excess proton accumulation and acidity stress.

The trans-Golgi network (TGN) serves as a platform to sort and transport proteins to their final destinations. Here the authors show that the TGN of Arabidopsis consists of spatially and temporally distinct subregions and propose that these zones may sort cargo to different destinations.

The nuclear lamina regulates chromatin organization and gene positioning. Here the authors show that CROWDED NUCLEI proteins contribute to the meshwork lamina structure in Arabidopsis nuclei and regulate copper tolerance by promoting lamina association and expression of copper response genes.

Mobilisation of seed storage reserves is important for seedling establishment in Arabidopsis. In this process, sucrose is synthesised from triacylglycerol via core metabolic processes. Mutants with defects in triacylglycerol-to-sucrose conversion display short etiolated seedlings. We found that whereas sucrose content in the indole-3-butyric acid response 10 (ibr10) mutant was significantly reduced, hypocotyl elongation in the dark was unaffected, questioning the role of IBR10 in this process. To dissect the metabolic complexity behind cell elongation, a quantitative-based phenotypic analysis combined with a multi-platform metabolomics approach was applied. We revealed that triacylglycerol and diacylglycerol breakdown were disrupted in ibr10, resulting in low sugar content and poor photosynthetic ability. Importantly, batch-learning self-organised map clustering revealed that threonine level was correlated with hypocotyl length. Consistently, exogenous threonine supply stimulated hypocotyl elongation, indicating that sucrose levels are not always correlated with etiolated seedling length, suggesting the contribution of amino acids in this process.

Cell wall pits allow movement of water between xylem vessels and are formed via Rho-GTPase mediated signaling that leads to local microtubule disassembly. Here, Sugiyama et al. show that an additional Rho-GTPase pathway controls cell wall deposition and actin dynamics to form pit boundaries.

Land plant shoot structures evolved a diversity of lateral organs as morphological adaptations to the terrestrial environment, with lateral organs arising independently in different lineages. Vascular plants and bryophytes (basally diverging land plants) develop lateral organs from meristems of sporophytes and gametophytes, respectively. Understanding the mechanisms of lateral organ development among divergent plant lineages is crucial for understanding the evolutionary process of morphological diversification of land plants. However, our current knowledge of lateral organ differentiation mechanisms comes almost entirely from studies of seed plants, and thus, it remains unclear how these lateral structures evolved and whether common regulatory mechanisms control the development of analogous lateral organs. Here, we performed a mutant screen in the liverwort Marchantia polymorpha, a bryophyte, which produces gametophyte axes with nonphotosynthetic scalelike lateral organs. We found that an Arabidopsis LIGHT-DEPENDENT SHORT HYPOCOTYLS 1 and Oryza G1 (ALOG) family protein, named M. polymorpha LATERAL ORGAN SUPRESSOR 1 (MpLOS1), regulates meristem maintenance and lateral organ development in Marchantia. A mutation in MpLOS1, preferentially expressed in lateral organs, induces lateral organs with misspecified identity and increased cell number and, furthermore, causes defects in apical meristem maintenance. Remarkably, MpLOS1 expression rescued the elongated spikelet phenotype of a MpLOS1 homolog in rice. This suggests that ALOG genes regulate the development of lateral organs in both gametophyte and sporophyte shoots by repressing cell divisions. We propose that the recruitment of ALOG-mediated growth repression was in part responsible for the convergent evolution of independently evolved lateral organs among highly divergent plant lineages, contributing to the morphological diversification of land plants.

High humidity decreases the penetration rate of barley powdery mildew Blumeria graminis f. sp. hordei. However, the mechanism is not well understood. In this study, the morphological and cytochemical analyses revealed that substances containing proteins leaked from the tip of the appressorial germ tube of conidia without the formation of appressorium under a high humidity condition. In addition, exposure to high humidity prior to the formation of appressorium caused the aberrant formation of the appressorial germ tube without appressorium formation, resulting in failure to penetrate the host cell. These findings suggest that the formation and maturation of the appressorium requires a low humidity condition, and will be clues to improve the disease management by humidity control.

The plastid evolved from a symbiotic cyanobacterial ancestor and is an essential organelle for plant life, but its developmental roles in roots have been largely overlooked. Here, we show that plastid translation is connected to the stem cell patterning in lateral root primordia. The RFC3 gene encodes a plastid-localized protein that is a conserved bacterial ribosomal protein S6 of β/γ proteobacterial origin. The rfc3 mutant developed lateral roots with disrupted stem cell patterning and associated with decreased leaf photosynthetic activity, reduced accumulation of plastid rRNAs in roots, altered root plastid gene expression, and changes in expression of several root stem cell regulators. These results suggest that deficiencies in plastid function affect lateral root stem cells. Treatment with the plastid translation inhibitor spectinomycin phenocopied the defective stem cell patterning in lateral roots and altered plastid gene expression observed in the rfc3 mutant. Additionally, when prps17 defective in a plastid ribosomal protein was treated with low concentrations of spectinomycin, it also phenocopied the lateral root phenotypes of rfc3. The spectinomycin treatment and rfc3 mutation also negatively affected symplasmic connectivity between primary root and lateral root primordia. This study highlights previously unrecognized functions of plastid translation in the stem cell patterning in lateral roots.

Drought causes substantial reductions in crop yields worldwide. Therefore, we set out to identify new chemical and genetic factors that regulate drought resistance in Arabidopsis thaliana. Karrikins (KARs) are a class of butenolide compounds found in smoke that promote seed germination, and have been reported to improve seedling vigor under stressful growth conditions. Here, we discovered that mutations in KARRIKIN INSENSITIVE2 (KAI2), encoding the proposed karrikin receptor, result in hypersensitivity to water deprivation. We performed transcriptomic, physiological and biochemical analyses of kai2 plants to understand the basis for KAI2-regulated drought resistance. We found that kai2 mutants have increased rates of water loss and drought-induced cell membrane damage, enlarged stomatal apertures, and higher cuticular permeability. In addition, kai2 plants have reduced anthocyanin biosynthesis during drought, and are hyposensitive to abscisic acid (ABA) in stomatal closure and cotyledon opening assays. We identified genes that are likely associated with the observed physiological and biochemical changes through a genome-wide transcriptome analysis of kai2 under both well-watered and dehydration conditions. These data provide evidence for crosstalk between ABA- and KAI2-dependent signaling pathways in regulating plant responses to drought. A comparison of the strigolactone receptor mutant d14 (DWARF14) to kai2 indicated that strigolactones also contributes to plant drought adaptation, although not by affecting cuticle development. Our findings suggest that chemical or genetic manipulation of KAI2 and D14 signaling may provide novel ways to improve drought resistance.

Water contamination by heavy metals from industrial activities is a serious environmental concern. To mitigate heavy metal toxicity and to recover heavy metals for recycling, biomaterials used in phytoremediation and bio-sorbent filtration have recently drawn renewed attention. The filamentous protonemal cells of the moss Funaria hygrometrica can hyperaccumulate lead (Pb) up to 74% of their dry weight when exposed to solutions containing divalent Pb. Energy-dispersive X-ray spectroscopy revealed that Pb is localized to the cell walls, endoplasmic reticulum-like membrane structures, and chloroplast thylakoids, suggesting that multiple Pb retention mechanisms are operating in living F. hygrometrica. The main Pb-accumulating compartment was the cell wall, and prepared cell-wall fractions could also adsorb Pb. Nuclear magnetic resonance analysis showed that polysaccharides composed of polygalacturonic acid and cellulose probably serve as the most effective Pb-binding components. The adsorption abilities were retained throughout a wide range of pH values, and bound Pb was not desorbed under conditions of high ionic strength. In addition, the moss is highly tolerant to Pb. These results suggest that the moss F. hygrometrica could be a useful tool for the mitigation of Pb-toxicity in wastewater.

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This paper proposes total optimization of energy networks in a smart city by multi-population global-best modified brain storm optimization (MP-GMBSO). Efficient utilization of energy is necessary for reduction of CO2 emission, and smart city demonstration projects have been conducted around the world in order to reduce total energies and the amount of CO2 emission. The problem can be formulated as a mixed integer nonlinear programming (MINLP) problem and various evolutionary computation techniques such as particle swarm optimization (PSO), differential evolution (DE), Differential Evolutionary Particle Swarm Optimization (DEEPSO), Brain Storm Optimization (BSO), Modified BSO (MBSO), Global-best BSO (BSO), and Global-best Modified Brain Storm Optimization (GMBSO) have been applied to the problem. However, there is still room for improving solution quality. Multi-population based evolutionary computation methods have been verified to improve solution quality and the approach has a possibility for improving solution quality. The proposed MS-GMBSO utilizes only migration for multi-population models instead of abest, which is the best individual among all of sub-populations so far, and both migration and abest. Various multi-population models, migration topologies, migration policies, and the number of sub-populations are also investigated. It is verified that the proposed MP-GMBSO based method with ring topology, the W-B policy, and 320 individuals is the most effective among all of multi-population parameters.

Shikonin derivatives are specialized lipophilic metabolites, secreted in abundant amounts from the root epidermal cells of Lithospermum erythrorhizon. Because they have anti-microbial activities, these compounds, which are derivatives of red naphthoquinone, are thought to serve as a chemical barrier for plant roots. The mechanism by which they are secreted from cells is, however, largely unknown. The shikonin production system in L. erythrorhizon is an excellent model for studying the mechanism by which lipophilic compounds are secreted from plant cells, because of the abundant amounts of these compounds produced by L. erythrorhizon, the 0 to 100% inducibility of their production, the light-specific inhibition of production, and the visibility of these products as red pigments. To date, many factors regulating shikonin biosynthesis have been identified, but no mechanism that regulates shikonin secretion without inhibiting biosynthesis has been detected. This study showed that inhibitors of membrane traffic strongly inhibit shikonin secretion without inhibiting shikonin production, suggesting that the secretion of shikonin derivatives into the apoplast utilizes pathways common to the ADP-ribosylation factor/GTPase-activating protein (ARF/GAP) system and actin filament polymerization, at least in part. These findings provide clues about the machinery involved in secreting lipid-soluble metabolites from cells.

Maintenance of plastid and mitochondrial genome stability is crucial for photosynthesis and respiration, respectively. Recently, we have reported that RECA1 maintains mitochondrial genome stability by suppressing gross rearrangements induced by aberrant recombination between short dispersed repeats in the moss Physcomitrella patens. In this study, we studied a newly identified P. patens homolog of bacterial RecG helicase, RECG, some of which is localized in both plastid and mitochondrial nucleoids. RECG partially complements recG deficiency in Escherichia coli cells. A knockout (KO) mutation of RECG caused characteristic phenotypes including growth delay and developmental and mitochondrial defects, which are similar to those of the RECA1 KO mutant. The RECG KO cells showed heterogeneity in these phenotypes. Analyses of RECG KO plants showed that mitochondrial genome was destabilized due to a recombination between 8-79 bp repeats and the pattern of the recombination partly differed from that observed in the RECA1 KO mutants. The mitochondrial DNA (mtDNA) instability was greater in severe phenotypic RECG KO cells than that in mild phenotypic ones. This result suggests that mitochondrial genomic instability is responsible for the defective phenotypes of RECG KO plants. Some of the induced recombination caused efficient genomic rearrangements in RECG KO mitochondria. Such loci were sometimes associated with a decrease in the levels of normal mtDNA and significant decrease in the number of transcripts derived from the loci. In addition, the RECG KO mutation caused remarkable plastid abnormalities and induced recombination between short repeats (12-63 bp) in the plastid DNA. These results suggest that RECG plays a role in the maintenance of both plastid and mitochondrial genome stability by suppressing aberrant recombination between dispersed short repeats; this role is crucial for plastid and mitochondrial functions.

Cone thermogenesis is a widespread phenomenon in cycads and may function to promote volatile emissions that affect pollinator behavior. Given their large population size and intense and durable heat-producing effects, cycads are important organisms for comprehensive studies of plant thermogenesis. However, knowledge of mitochondrial morphology and function in cone thermogenesis is limited. Therefore, we investigated these mitochondrial properties in the thermogenic cycad species Cycas revoluta. Male cones generated heat even in cool weather conditions. Female cones produced heat, but to a lesser extent than male cones. Ultrastructural analyses of the two major tissues of male cones, microsporophylls and microsporangia, revealed the existence of a population of mitochondria with a distinct morphology in the microsporophylls. In these cells, we observed large mitochondria (cross-sectional area of 2 μm² or more) with a uniform matrix density that occupied >10% of the total mitochondrial volume. Despite the size difference, many nonlarge mitochondria (cross-sectional area <2 μm²) also exhibited a shape and a matrix density similar to those of large mitochondria. Alternative oxidase (AOX) capacity and expression levels in microsporophylls were much higher than those in microsporangia. The AOX genes expressed in male cones revealed two different AOX complementary DNA sequences: CrAOX1 and CrAOX2. The expression level of CrAOX1 mRNA in the microsporophylls was 100 times greater than that of CrAOX2 mRNA. Collectively, these results suggest that distinctive mitochondrial morphology and CrAOX1-mediated respiration in microsporophylls might play a role in cycad cone thermogenesis. [ABSTRACT FROM AUTHOR]

Hyperphosphatemia is a secondary health issue that arises during chronic kidney disorder (CKD). Phosphate binders and dialysis are prescribed in later stages of CKD, although they may lead to harmful side-effects and worsen quality of life. Therefore, we examined the potential of intestinal bacteria (lactic acid bacteria and bifidobacteria) as phosphate-accumulating organisms (PAOs), whether PAO-formulated food can prevent CKD at earlier stages. Among the experimental organisms, Bifidobacterium adolescentis JCM1275 was the most effective. The effects of prebiotic and soy peptides were also evaluated where fructooligosaccharide was found to further enhance phosphate accumulation by B. adolescentis JCM1275, resulting in the best phosphate accumulation activity, identified in the study. Therefore, certain bifidobacteria and lactic acid bacteria strains have the potential to act as biological phosphate accumulators and contribute to the prevention of CKD pathology and improve patient outcome by care (not cure by medicines). [ABSTRACT FROM AUTHOR]

Stress granules, a type of cytoplasmic RNA granule in eukaryotic cells, are induced in response to various environmental stresses, including high temperature. However, how high temperatures induce the formation of these stress granules in plant cells is largely unknown. Here, we characterized the process of stress granule formation in Arabidopsis thaliana by combining live imaging and electron microscopy analysis. In seedlings grown at 22°C, stress granule formation was induced at temperatures above a critical threshold level of 34°C in the absence of transpiration. The threshold temperature was the same, regardless of whether the seedlings were grown at 22°C or 4°C. High-resolution live imaging microscopy revealed that stress granule formation is not correlated with the sizes of pre-existing RNA processing bodies (P-bodies) but that the two structures often associated rapidly. Immunoelectron microscopy revealed a previously unidentified characteristic of the fine structures of Arabidopsis stress granules and P-bodies: the lack of ribosomes and the presence of characteristic electron-dense globular and filamentous structures. These results provide new insights into the universal nature of stress granules in eukaryotic cells. [ABSTRACT FROM AUTHOR]

Starch granule morphology differs markedly among plant species. However, the mechanisms controlling starch granule morphology have not been elucidated. Rice (Oryza sativa) endosperm produces characteristic compound-type granules containing dozens of polyhedral starch granules within an amyloplast. Some other cereal species produce simple-type granules, in which only one starch granule is present per amyloplast. A double mutant rice deficient in the starch synthase (SS) genes SSIIIa and SSIVb (ss3a ss4b) produced spherical starch granules, whereas the parental single mutants produced polyhedral starch granules similar to the wild type. The ss3a ss4b amyloplasts contained compound-type starch granules during early developmental stages, and spherical granules were separated from each other during subsequent amyloplast development and seed dehydration. Analysis of glucan chain length distribution identified overlapping roles for SSIIIa and SSIVb in amylopectin chain synthesis, with a degree of polymerization of 42 or greater. Confocal fluorescence microscopy and immunoelectron microscopy of wild-type developing rice seeds revealed that the majority of SSIVb was localized between starch granules. Therefore, we propose that SSIIIa and SSIVb have crucial roles in determining starch granule morphology and in maintaining the amyloplast envelope structure. We present a model of spherical starch granule production. [ABSTRACT FROM AUTHOR]

Abstract  Circular dichroism (CD) and absorption spectra were measured for acridine orange derivatives: 3,6-bis(dimethylamino) acridine (AO), 3,6-bis(dimethylamino)-10-methylacridinium bromide (C1AO), and 3,6-bis(dimethylamino)-10-dodecylacridinium bromide (C12AO) in aqueous dodecanoyl-l-threonine (C12Thr) solutions at 30, 40, 50, and 60 °C and pH 8–9. CD spectra were not induced for AO and C1AO in C12Thr aqueous solutions. Induced circular dichroism (ICD) based on the exciton interaction was found for premicellar aggregates of C12AO with C12Thr, but the micellar aggregates failed to induce CD for solubilized C12AO at a higher concentration than C12Thr critical micelle concentration. The maximum ICD intensity was observed for 1:1.2 aggregates of C12AO and C12Thr. The ICD spectrum indicated positive chirality at 30 °C, but negative chirality at 50 °C. The chirality transition occurred at 40∼45 °C. The slow change in both the absorption and ICD spectra is ascribed partly to the rearrangement of dye alignment and partly to the growth of the aggregate; the system reaches final phase separation after a few days. [ABSTRACT FROM AUTHOR]

The development of cells specialized for water conduction or support is a striking innovation of plants that has enabled them to colonize land. The NAC transcription factors regulate the differentiation of these cells in vascular plants. However, the path by which plants with these cells have evolved from their nonvascular ancestors is unclear. We investigated genes of the moss Physcomitrella patens that encode NAC proteins. Loss-of-function mutants formed abnormal water-conducting and supporting cells, as well as malformed sporophyte cells, and overexpression induced ectopic differentiation of water-conducting--like cells. Our results show conservation of transcriptional regulation and cellular function between moss and Arabidopsis thaliana water-conducting cells. The conserved genetic basis suggests roles for NAC proteins in the adaptation of plants to land. [ABSTRACT FROM AUTHOR]