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Intronic trinucleotide repeat (TNR) is widely distributed in plant genomes. In Arabidopsis accession Bur-0, abnormally expanded TTC repeat in intron-3 of theISOPROPYLMALATE ISOMERASE LARGE SUBUNIT1(IIL1) gene causes growth defects called theirregularly impaired leaves(iil) phenotype, triggered by DNA methylation-mediatedIIL1gene silencing at elevated temperature. However, little is known about how the reduced expression ofIIL1causes theiilphenotype. We demonstrated that theiilphenotype was resulted from the relative increase of intron-3-retainedIIL1transcripts through the experiments where theiilphenotype was reproduced by introducing theIIL1gene harboring 100 copies of TTC repeat into Col-0. Theiilphenotype appeared when the total amount of theIIL1transcripts was decreased by co-suppression and the percentage of intron-3-retainedIIL1transcripts was increased. TheIIL1gene encodes an isopropylmalate isomerase large subunit, forming heterodimers with small subunits (AtLeuD1, AtLeuD2, or AtLeuD3). In themyb28 myb29mutant lacking AtLeuD1 and AtLeuD2, theiilphenotype was almost completely suppressed regardless of higher percentage of intron-3-retainedIIL1transcripts. The results indicated that theiilphenotype was associated with interaction with AtLeuDs, suggesting that intronic TNR-containing transcripts were translated into abnormal proteins and perturbed the metabolic pathway supporting the leaf development.

Foods contain not only nutrients but also a wide variety of components related to flavor and functionality. Many studies have been conducted on the components of foods. Quantitative analysis has been used to assess compounds in food such as sugars, amino acids, and organic acids for food flavor; carotenoids and anthocyanins for appearance and color; and vitamins related to functionality for human health. Plants and animals that are food materials are thought to contain hundreds to thousands of compounds. Recent improvements in analytical technologies have made it possible to detect a large number of compounds simultaneously using metabolomics, a comprehensive analysis technology for low-molecular-weight compounds, and its application to food analysis has been reported. Food metabolomics has the potential to identify compounds related to flavor and functionality that have not been reported in previous studies; moreover, it is expected to add value to the target foods. By integrating the results of sensory evaluation, animal experiments, and other experiments with metabolomic data and providing them for analysis using informatics, such as artificial intelligence, it may be possible to derive more accurate evaluations of food quality.

Overexpressing Nicotinamidase 3 gene, and the exogenous application of its metabolite nicotinic acid (NA), enhance drought stress tolerance and increase biomass in Arabidopsis thaliana. With progressive global climatic changes, plant productivity is threatened severely by drought stress. Deciphering the molecular mechanisms regarding genes responsible for balancing plant growth and stress amelioration could imply multiple possibilities for future sustainable goals. Nicotinamide adenine dinucleotide (NAD) biosynthesis and recycling/ distribution is a crucial feature for plant growth. The current study focuses on the functional characterization of nicotinamidase 3 (NIC3) gene, which is involved in the biochemical conversion of nicotinamide (NAM) to nicotinic acid (NA) in the salvage pathway of NAD biosynthesis. Our data show that overexpression of NIC3 gene enhances drought stress tolerance and increases plant growth. NIC3-OX plants accumulated more NA as compared to WT plants. Moreover, the upregulation of several genes related to plant growth/stress tolerance indicates that regulating the NAD salvage pathway could significantly enhance plant growth and drought stress tolerance. The exogenous application of nicotinic acid (NA) showed a similar phenotype as the effect of overexpressing NIC3 gene. In short, we contemplated the role of NIC3 gene and NA application in drought stress tolerance and plant growth. Our results would be helpful in engineering plants with enhanced drought stress tolerance and increased growth potential.

The highly phosphorylated nucleotide, guanosine tetraphosphate (ppGpp), functions as a secondary messenger in bacteria and chloroplasts. The accumulation of ppGpp alters plastidial gene expression and metabolism, which are required for proper photosynthetic regulation and robust plant growth. However, because four plastid-localized ppGpp synthases/hydrolases function redundantly, the impact of the loss of ppGpp-dependent stringent response on plant physiology remains unclear. We used the CRISPR/Cas9 technology to generate an Arabidopsis thaliana mutant lacking all four ppGpp synthases/hydrolases, and characterized its phenotype. The mutant showed 20-fold less ppGpp levels than the wild type (WT) under normal growth conditions, and exhibited leaf chlorosis and increased expression of defense-related genes as well as salicylic acid and jasmonate levels upon transition to nitrogen-starvation conditions. These results demonstrate that proper levels of ppGpp in plastids are required for controlling not only plastid metabolism but also phytohormone signaling, which is essential for plant defense.

Arbuscular mycorrhizal (AM) fungal extraradical hyphae exude their metabolites into the soil. Root exudate metabolites are affected by plant species and P status. However, the effect of P status on AM hyphal exudate metabolites has been unknown. This study aimed to examine hyphal exudate metabolite composition of two AM fungal species and their response to P deficiency through metabolite profiling. Rhizophagus clarus and R. irregularis were grown in a two-compartment in vitro culture system of Linum usitatissimum roots on solid modified Strullu-Romand medium in combination with two P levels (3 µM (P3) and 30 µM (P30)). Hyphal exudates were collected from the hyphal compartment at 118 days after inoculation (DAI). The metabolite composition of the hyphal exudates was determined by capillary electrophoresis/time-of-flight mass spectrometry, resulting in the identification of a total of 141 metabolites at 118 DAI. In the hyphal exudates of R. clarus, the concentrations of 18 metabolites, including sugars, amino acids, and organic acids, were significantly higher (p

Root exudates of soybean grown under low-, normal-, and high-K+ conditions were evaluated using metabolomics. Two soybean cultivars, ‘Satonohohoemi’ (low-K-tolerant) and ‘Tachinagaha’ (low-K sensitive), were hydroponically grown with 6 (K6), 60 (K60), and 120 (K120) mg K L−1 for 7 and 14 days after transplanting (DAT). Root exudates were collected, and metabolites were evaluated using capillary electrophoresis time-of-flight mass spectrometry. Rroot K concentration was lower in K6 and higher in K120 compared to K60. Number of metabolites detected in ‘Satonohohoemi’ and ‘Tachinagaha’ was 43 and 39, respectively. Score plot of the principal component analysis (PCA) showed a clear grouping of the root exudate metabolites based one three K concentrations and two sampling times, with the first PCA accounting for 65.7% and 71.5% of the variance for the ‘Satonohohoemi’ and ‘Tachinagaha’, respectively. High-K conditions enhanced release of root exudate metabolites to rhizosphere in both soybean cultivars from 18% to 42%. However, low-K conditions resulted in a 1.2-fold increase and a 2.5-fold decrease in the release of root exudate metabolites in ‘Tachinagaha’ and ‘Satonohohoemi’, respectively, at 7 and 14 DAT. These results reveal that soybean roots exude many metabolites in response to high- and low-K conditions. The number of increased metabolites was higher after long-term (14 DAT) compared to that of the short-term (7 DAT) of exposure of high- and low-K conditions. Soybean cultivars differ in the capacity to release metabolites by altering the exudation of specific metabolites for a better adaptation to the high- and low-K conditions.

Integrative omics approaches revealed a crosstalk among phytohormones during tuberous root development in cassava. Tuberous root formation is a complex process consisting of phase changes as well as cell division and elongation for radial growth. We performed an integrated analysis to clarify the relationships among metabolites, phytohormones, and gene transcription during tuberous root formation in cassava (Manihot esculenta Crantz). We also confirmed the effects of the auxin (AUX), cytokinin (CK), abscisic acid (ABA), jasmonic acid (JA), gibberellin (GA), brassinosteroid (BR), salicylic acid, and indole-3-acetic acid conjugated with aspartic acid on tuberous root development. An integrated analysis of metabolites and gene expression indicated the expression levels of several genes encoding enzymes involved in starch biosynthesis and sucrose metabolism are up-regulated during tuberous root development, which is consistent with the accumulation of starch, sugar phosphates, and nucleotides. An integrated analysis of phytohormones and gene transcripts revealed a relationship among AUX signaling, CK signaling, and BR signaling, with AUX, CK, and BR inducing tuberous root development. In contrast, ABA and JA inhibited tuberous root development. These phenomena might represent the differences between stem tubers (e.g., potato) and root tubers (e.g., cassava). On the basis of these results, a phytohormonal regulatory model for tuberous root development was constructed. This model may be useful for future phytohormonal studies involving cassava.

Human induced pluripotent stem cells (iPSCs) require high levels of methionine (Met). Met deprivation results in a rapid decrease in intracellular S-adenosyl-methionine (SAM), poising human iPSCs for differentiation and leading to the apoptosis of undifferentiated cells. Met deprivation triggers rapid metabolic changes, including SAM, followed by reversible epigenetic modifications. Here, we show that short-term Met deprivation impairs the pluripotency network through epigenetic modification in a 3D suspension culture. The trimethylation of lysine 4 on histone H3 (H3K4me3) was drastically affected compared with other histone modifications. Short-term Met deprivation specifically affects the transcription start site (TSS) region of genes, such as those involved in the transforming growth factor β pathway and cholesterol biosynthetic process, besides key pluripotent genes such as NANOG and POU5F1. The expression levels of these genes decreased, correlating with the loss of H3K4me3 marks. Upon differentiation, Met deprivation triggers the upregulation of various lineage-specific genes, including key definitive endoderm genes, such as GATA6. Upon differentiation, loss of H3K27me3 occurs in many endodermal genes, switching from a bivalent to a monovalent (H3K4me3) state. In conclusion, Met metabolism maintains the pluripotent network with histone marks, and their loss potentiates differentiation.

The Arabidopsis ppGpp-overproducing mutant indicates a larger biomass than wild type by modulated amino-acid metabolism under nitrogen-limiting conditions. The regulatory nucleotide, guanosine 3', 5'-bis(pyrophosphate; ppGpp)-originally identified in Escherichia coli-controls gene expression and enzyme activities in the bacteria and plastids of plant cells. We recently reported that the ppGpp over-producing mutant of Arabidopsis thaliana had a larger shoot weight than wild type (WT), especially under nutrient-deficient conditions. However, the mechanisms behind the influence of ppGpp on plant growth and biomass remain elusive. To understand the impact of the ppGpp accumulation on plant growth, we characterized metabolic changes in the ppGpp-overproducing mutant upon transition from nitrogen-rich to nitrogen-limiting concentrations. We found that the fresh weight of the mutant was significantly larger than WT when the total nitrogen source (KNO

Phenylacetic acid (PAA) is one type of natural auxin and widely exists in plants. Previous biochemical studies demonstrate that PAA in plants is synthesized from phenylalanine (Phe) via phenylpyruvate (PPA), but the PAA biosynthetic genes and its regulation remain unknown. In this article, we show that the AROGENATE DEHYDRATASE (ADT) family, which catalyzes the conversion of arogenate to Phe, can modulate the levels of PAA in Arabidopsis. We found that overexpression of ADT4 or ADT5 remarkably increased the amounts of PAA. Due to an increase in PAA levels, ADT4ox and ADT5ox plants can partially restore the auxin-deficient phenotypes caused by treatments with an inhibitor of the biosynthesis of indole-3-acetic acid (IAA), a main auxin in plants. In contrast, the levels of PAA were significantly reduced in adt multiple knockout mutants. Moreover, the levels of PPA are substantially increased in ADT4 or ADT5 overexpression plants but reduced in adt multiple knockout mutants, suggesting that PPA is a key intermediate of PAA biosynthesis. These results provide an evidence that members of the ADT family of Arabidopsis can modulate PAA level via the PPA-dependent pathway.

In northeastern Japan, an area of high precipitation and mountains, beech (Fagus creanata Blume), larch (Larix kaempferi Lamb.), cedar (Cryptomeria japonica D. Don) and black locust (Robinia pseudoacacia L.) were evaluated for N resorption and N isotope fractionation in pre- and post-abscission leaves in comparison to green leaves. The highest leaf N concentration in summer corresponded to the N-fixing black locust, followed in decreasing order by the deciduous beech and larch and evergreen cedar. On the other hand, the lowest N resorption efficiency corresponded to black locust and the highest to beech, in increasing order by larch and cedar. All tree species returned significant amounts of N before leaf abscission; however, N isotope fractionation during leaf N resorption was only found for beech, with a depleted N isotope value from green to pre-abscission leaf. The most N, however, was resorbed from pre-abscission to post-abscission. This result may indicate that δ15N fractionation took place during N transformation processes, such as protein hydrolysis, when the concentration of free amino acids increased sharply. The difference in the type of amino acid produced by each species could have influenced the N isotope ratio in beech but not in the other tree species. The results of this study showed that it is possible to infer the type and timing of processes relevant to N resorption by analyzing leaf δ15N variation during senescence.

Nitrogen withdrawal from senescing leaves in evergreen trees is assumed to be stored mainly in the remaining leaves at the end of the growing season. However, there is evidence that roots as well as stem tissues play a significant role in nitrogen and other nutrients storage. Therefore, the objective of this study is to clarify the seasonal nitrogen cycle in Japanese cedar trees in order to elucidate its N storage strategy. N content, isotope ratio and amino acids content were measured in coarse roots, sapwood, leaves (separated by age), litter and buds along the growing season. Nitrogen content increased from the shoot growth to the post-abscission period with younger leaves storing more N than older ones. N from senescent leaves was reabsorbed to roots in October and to sapwood and the remaining leaves in November accounting for only 5% of whole-tree stored N. No temporal N isotopic fractionation was observed in plant tissues except for leaf enrichment during storage. The variation of amino acids in leaf tissues explained internal N transport. Japanese cedar trees reabsorbed leaf N and soil N in the pre-abscission period and stored most N in roots (54%) and sapwood (20%) followed by leaves (18%) and branches (8%), respectively.

Plants release various metabolites from roots and root exudates contribute to differences in stress tolerance among plant species. Plant and soil microbes have complex interactions that are affected by biotic and abiotic factors. The purpose of this study was to examine the differences in metabolites in root exudates of rice (Oryza sativa) cultivars and their correlation with bacterial populations in the rhizosphere. Two rice cultivars (O. sativa cv. Akamai and O. sativa cv. Koshihikari) were grown in soils fertilized with 0 g P kg−1 (− P) or 4.8 g P kg−1 (+ P). Root exudates and root-attached soil were collected at 13 and 20 days after transplanting (DAT) and their metabolites and bacterial community structure were determined. The exudation of proline, serine, threonine, valine and 4-coumarate were increased under low P conditions in both cultivars. There was a positive correlation between the concentration of pantothenate in root exudates and the representation of members of the genera Clostridium and Sporosarcina, which were negatively correlated with root dry weight. Gracilibacter, Opitutus, Pelotomaculum, Phenylobacterium and Oxobacter were positively correlated with root dry weight and presence of allantoin, 2-aminobtyrate and GlcNac. This study provides new information about the response of plants and rhizosphere soil bacteria to low P conditions.

Understanding the limiting factors of grain filling is essential for the further improvement of grain yields in rice (Oryza sativa). The relatively slow grain growth of the high-yielding cultivar ‘Momiroman’ is not improved by increasing carbon supply, and hence low sink activity (i.e. the metabolic activity of assimilate consumption/storage in sink organs) may be a limiting factor for grain filling. However, there is no metabolic evidence to corroborate this hypothesis, partly because there is no consensus on how to define and quantify sink activity. In this study, we investigated the carbon flow at a metabolite level from photosynthesis in leaves to starch synthesis in grains of three high-yielding cultivars using the stable isotope 13C. We found that a large amount of newly fixed carbon assimilates in Momiroman was stored as hexose instead of being converted to starch. In addition, the activity of ADP-glucose pyrophosphorylase and the expression of AGPS2b, which encodes a subunit of the ADP-glucose pyrophosphorylase enzyme, were both lower in Momiroman than in the other two cultivars in grains in superior positions on panicle branches. Hence, slower starch synthesis from hexose, which is partly explained by the low expression level of AGPS2b, may be the primary metabolic reason for the lower sink activity observed in Momiroman.

Guanosine 3′,5′-bis(pyrophosphate) (ppGpp) functions as a second messenger in bacteria to adjust their physiology in response to environmental changes. In recent years, the ppGpp-specific hydrolase, metazoan SpoT homolog-1 (Mesh1), was shown to have important roles for growth under nutrient deficiency in Drosophila melanogaster. Curiously, however, ppGpp has never been detected in animal cells, and therefore the physiological relevance of this molecule, if any, in metazoans has not been established. Here, we report the detection of ppGpp in Drosophila and human cells and demonstrate that ppGpp accumulation induces metabolic changes, cell death, and eventually lethality in Drosophila. Our results provide the evidence of the existence and function of the ppGpp-dependent stringent response in animals., Ito et al. succeed in detecting guanosine tetraphosphate (ppGpp) in measurable levels in metazoan, specifically in Drosophila. They further demonstrate that the ppGpp-specific hydrolase, metazoan SpoT homolog-1 (Mesh1), is necessary, at least in certain conditions, to maintain low ppGpp levels, hence providing insights into the role of Mesh1 as a ppGpp hydrolase in vivo.

Rice varieties that can survive under submergence conditions respond to flooding either by enhancing internode elongation or by quiescence of shoot elongation. Despite extensive efforts to identify key metabolites triggered by complete submergence of rice possessing SUBMERGENCE 1 (SUB1) locus, metabolic responses of internode elongation of deepwater rice governed by the SNORKEL 1 and 2 genes remain elusive. This study investigated specific metabolomic responses under partial submergence (PS) to deepwater- (C9285) and non-deepwater rice cultivars (Taichung 65 (T65)). In addition, we examined the response in a near-isogenic line (NIL-12) that has a C9285 genomic fragment on chromosome 12 introgressed into the genetic background of T65. Under short-term submergence (0−24 h), metabolite profiles of C9285, NIL-12, and T65 were compared to extract significantly changed metabolites in deepwater rice under PS conditions. Comprehensive metabolite and phytohormone profiling revealed increases in metabolite levels in the glycolysis pathway in NIL-12 plants. Under long-term submergence (0−288 h), we found decreased amino acid levels. These metabolomic changes were opposite when compared to those in flood-tolerant rice with SUB1 locus. Auxin conjugate levels related to stress response decreased in NIL-12 lines relative to T65. Our analysis helped clarify the complex metabolic reprogramming in deepwater rice as an escape strategy.

Shoot formation is accompanied by active cell proliferation and expansion, which requires adaptation of the metabolic state to allow for developmental control. Despite the importance of such metabolic reprogramming, it remains unclear how development and metabolism are integrated. In this study, we showed that disruption of ANGUSTIFOLIA3 orthologs (PpAN3s) compromised gametophore shoot formation in the moss Physcomitrella patens due to defective cell proliferation and expansion. Trans-omics analysis revealed that the downstream activity of PpAN3 is linked to arginine metabolism. Elevating arginine level by chemical treatment led to stunted gametophores and caused Ppan3 mutant-like transcriptional changes in the wild-type plant. Furthermore, ectopic expression of AtAN3 from Arabidopsis thaliana ameliorated the defective arginine metabolism and promoted gametophore formation in Ppan3 mutants. Together, these findings indicate that arginine metabolism is a key pathway associated with gametophore formation and provide evolutionary insights into the establishment of the shoot system in land plants through the integration of developmental and metabolic processes.

Summary Aflatoxin contamination of crops is a serious problem worldwide. Utilization of aflatoxin production inhibitors is attractive, as the elucidation of their modes of action contributes to clarifying the mechanism of aflatoxin production. Here, we identified mitochondrial protease ClpP as the target of dioctatin, an inhibitor of aflatoxin production of Aspergillus flavus. Dioctatin conferred uncontrolled caseinolytic capacity on ClpP of A. flavus and Escherichia coli. Dioctatin-bound ClpP selectively degraded mitochondrial energy-related proteins in vitro, including a subunit of respiratory chain complex V, which was also reduced by dioctatin in a ClpP-dependent manner in vivo. Dioctatin enhanced glycolysis and alcohol fermentation while reducing tricarboxylic acid cycle metabolites. These disturbances were accompanied by reduced histone acetylation and reduced expression of aflatoxin biosynthetic genes. Our results suggest that dioctatin inhibits aflatoxin production by inducing ClpP-mediated degradation of mitochondrial energy-related components, and that mitochondrial energy metabolism functions as a key determinant of aflatoxin production.

Background and Motivation: Nitrogen content in tissues of Fagus crenata Blume is key for flowering and seed production. However, there is a lack of information on seasonal intra-plant nitrogen partitioning in this representative tree species typical of heavy snowfall regions in Japan. Therefore, the objective of this study was to elucidate Fagus crenata intra-plant nitrogen movement by means of nitrogen content, nitrogen isotope analysis, and amino acids temporal variability. Materials and Methods: Nitrogen content, isotope ratio, and free amino acids content were measured in coarse roots, sapwood, leaves, and litter in four phenological stages in nine adult Fagus crenata trees and upscaled to the whole-tree level. Results: Nitrogen was reabsorbed to and stored in coarse roots during the pre-abscission stage, as was revealed by the depletion of the δ15N ratio of coarse roots, which coincided with an enrichment of 15N found in leaves. During the post-abscission stage, N was stored in the sapwood, where an enrichment in 15N was found coinciding with the depletion of the δ15N ratio in leaves. It seemed that 15N-enriched nitrogen was initially reabsorbed from leaves to coarse roots during the pre-abscission period, followed by the reabsorption of 15N-enriched nitrogen from leaves to sapwood shortly before leaf abscission. Free amino acids content and their dynamics could mostly explain seasonal δ15N fractionation in leaves, coarse roots, and partially in sapwood. At the whole-tree level, N content stored in coarse roots and sapwood was similar. Furthermore, reabsorbed leaf N accounted for 32% of all nitrogen stored during leaf senescence. Conclusion: We found three phases of nitrogen storage revealed by δ15N fractionation during leaf senescence: (1) reabsorption of leaf 15N-depleted nitrogen to coarse roots, followed by (2) reabsorption of leaf 15N-enriched nitrogen to sapwood and (3) soil 15N-depleted nitrogen uptake to coarse roots. Further, changes in free amino acids, which are the result of enzyme activities involved in amino acids synthesis, partially explained δ15N fractionation in plant tissues.

TGR5, a G protein-coupled bile acid receptor, is expressed in various tissues and regulates several physiological processes. In the skeletal muscle, TGR5 activation is known to induce muscle hypertrophy; however, the effects on glucose and lipid metabolism are not well understood, despite the fact that the skeletal muscle plays a major role in energy metabolism. Here, we demonstrate that skeletal muscle-specific TGR5 transgenic (Tg) mice exhibit increased glucose utilization, without altering the expression of major genes related to glucose and lipid metabolism. Metabolite profiling analysis by capillary electrophoresis time-of-flight mass spectrometry showed that glycolytic flux was activated in the skeletal muscle of Tg mice, leading to an increase in glucose utilization. Upon long-term, high-fat diet challenge, blood glucose clearance was improved in Tg mice without an accompanying increase in insulin sensitivity in skeletal muscle and a reduction of body weight. Moreover, Tg mice showed improved age-associated glucose intolerance. These results strongly suggest that TGR5 ameliorated glucose metabolism disorder that is caused by diet-induced obesity and aging by enhancing the glucose metabolic capacity of the skeletal muscle. Our study demonstrates that TGR5 activation in the skeletal muscle is effective in improving glucose metabolism and may be beneficial in developing a novel strategy for the prevention or treatment of hyperglycemia.

The effects of exogenous GA4+7 and BA + CPPU treatments at flowering on fruit traits, lignin, and metabolome were investigated in fruit of Japanese pear “Gold Nijisseiki”. Analysis of fruits in all treatments showed that both total and noncondensed lignin content increased early in fruit development and decreased toward harvest and that the core had higher lignin content than the flesh. The core of BA + CPPU-treated fruit had higher maximum total lignin content than did GA4+7-treated and control fruit at early fruit development. At harvest, the total lignin and noncondensed lignin content of BA + CPPU-treated fruit was higher than that of GA4+7-treated and control fruit. The lignin was composed of guaiacyl-syringyl types and the syringyl/guaiacyl (S/G) ratio increased during early stages and remained relatively stable toward harvest. These results suggest that exogenous GA4+7 and BA + CPPU treatment affected only the lignin content, not the S/G ratio. In total, 122 substances were used for metabolome analysis. Partial least squares discriminant analysis first divided substances into clusters corresponding to core and flesh and then separated the clusters of substances associated with GA4+7 treatment from those associated with the BA + CPPU treatment and control. Of these 122 metabolites, 40 were subjected to hierarchical cluster analysis. Among these, 8 metabolites were more abundant in the pear fruit core. The remaining 32 metabolites were more abundant in flesh and differed in abundance among treatments. The functional metabolite arbutin was more abundant in core than in flesh. In contrast, beta-nicotinamide ribotide was more abundant in flesh than in core.

Aflatoxin contamination of crops is a serious problem impacting human health and the economy. Utilization of aflatoxin production inhibitors is attractive, as the elucidation of their modes of action provides clues to clarify the mechanism of aflatoxin production. Here, we identified mitochondrial protease ClpP as the molecular target of dioctatin, an inhibitor of aflatoxin production of Aspergillus flavus. Dioctatin conferred uncontrolled caseinolytic capacity on ClpP of A. flavus and Escherichia coli. Proteomic analysis showed that dioctatin-bound ClpP selectively degraded mitochondrial energy-related proteins, such as subunits of respiratory complexes and the pyruvate dehydrogenase complex. Dioctatin enhanced glycolysis and alcohol fermentation while reducing tricarboxylic acid cycle metabolites. These metabolic shifts accompanied the reduction of histone acetylation, leading to the downregulation of aflatoxin production. Our results suggest the existence of an exquisite balance between aflatoxin production and alcohol fermentation, with mitochondrial status serving as a key determinant of this balance.

Type II alveolar epithelial cells (AEC2s) play a crucial role in the regeneration of type I AECs after acute lung injury. The mechanisms underlying the regeneration of AEC2s are not fully understood. To address this issue, here, we investigated a murine model of acute lung injury using mice expressing human Diphtheria Toxin Receptor (DTR) under the control of Lysozyme M promoter (LysM-DTR). DT injection induced the depletion of AEC2s, alveolar macrophages, and bone marrow (BM)-derived myeloid cells in LysM-DTR mice, and the mice died within 6 days after DT injection. Apoptotic AEC2s and bronchiolar epithelial cells appeared at 24 hr, whereas Ki67-positive proliferating cells appeared in the alveoli and bronchioles in the lung of LysM-DTR mice at 72-96 hr after DT injection. Transfer of wild-type BM cells into LysM-DTR mice accelerated the regeneration of AEC2s along with the up-regulation of several growth factors. Moreover, several metabolites were significantly decreased in the sera of LysM-DTR mice compared with WT mice after DT injection, suggesting that these metabolites might be biomarkers to predict AEC2s injury. Together, LysM-DTR mice might be useful to identify growth factors to promote lung repair and the metabolites to predict the severity of lung injury.

Background It has been said that naturally occurring autopolyploid strains are more tolerant of biotic and/or abiotic stresses, due at least in part to the higher accumulation of secondary metabolites. Data supporting this hypothesis come from comparisons between naturally established autopolyploids and diploids; thus the high accumulation of metabolites in polyploid strains may be a secondarily acquired feature and not a direct effect of the autopolyploidy. But no detailed studies on this issue have been carried out. Results Here we carried out metabolome analyses between newly created tetraploids and the parent diploid in a model plant, Arabidopsis thaliana , and the agriculturally important pear fruit tree ( Pyrus communis var. sativa ). Our data showed that small numbers of metabolite species differ in amount between diploids and tetraploids in both species, but the differences were not reproducible among growth conditions and species. Conclusions These results strongly indicate that metabolite content is not universal nor the direct target of polyploidy-dependent changes. Instead, naturally occurring hyperaccumulation of metabolites in autopolyploids may be the result of secondary natural selection.