Alteration of shoaling behavior and dysbiosis in the gut of medaka (Oryzias latipes) exposed to 2-µm polystyrene microplastics.

There is global concern that microplastics may harm aquatic life. Here, we examined the effects of fine polystyrene microplastics (PS-MPs, 2-µm diameter, 0.1 mg/L, 2.5 × 107 particles/L) on the behavior and the microbiome (linked to brain-gut interaction) of a fish model using medaka, Oryzias latipes. We found that shoaling behavior was reduced in PS-MP-exposed medaka compared with control fish during the exposure period, but it recovered during a depuration period. There was no difference in swimming speed between the PS-MP-exposed and control groups during the exposure period. Analysis of the dominant bacterial population (those comprising ≥1% of the total bacterial population) in the gut of fish showed that exposure to PS-MPs tended to increase the relative abundance of the phylum Fusobacteria and the genus Vibrio. Furthermore, structural-equation modeling of gut bacteria on the basis of machine-learning data estimated strong relationship involved in the reduction of the functional bacterial species of minority (<1% of the total bacterial population) such as the genera Muribaculum (an undefined role), Aquaspirillum (a candidate for nitrate metabolism and magnetotactics), and Clostridium and Phascolarctobacterium (potential producers of short-chain fatty acids, influencing behavior by affecting levels of neurotransmitters) as a group of gut bacteria in association with PS-MP exposure. Our results suggest that fish exposure to fine microplastics may cause dysbiosis and ultimately cause social behavior disorders linked to brain-gut interactions. This effect could be connected to reduction of fish fitness in the ecosystem and reduced fish survival.

Uncommon Arrangement of Self-resistance Allows Biosynthesis of de novo Purine Biosynthesis Inhibitor that Acts as an Immunosuppressor.

(-)-FR901483 (1) isolated from the fungus Cladobotryum sp. No.11231 achieves immunosuppression via nucleic acid biosynthesis inhibition rather than IL-2 production inhibition as accomplished by FK506 and cyclosporin A. Recently, we identified the frz gene cluster for the biosynthesis of 1. It contains frzK, a gene homologous to phosphoribosyl pyrophosphate amidotransferase (PPAT)that catalyzes the initial step of de novo purine biosynthesis. We speculated that frzK encodes a PPAT that escapes inhibition by 1 and functions as a self-resistance enzyme (SRE) for the producing host. Nevertheless, details remained elusive. Here, we report the biochemical and structural analyses of FrzK and its Escherichia coli counterpart, PurF. Recombinantly produced FrzK exhibited PPAT activity, albeit weaker than PurF, but evaded strong inhibition by 1. These results confirmed that the target of 1 is PPAT, and FrzK acts as an SRE by maintaining the de novo purine biosynthetic capability in the presence of 1. To understand how FrzK evades inhibition by 1, we determined the crystal structure of PurF in the complex with 1 and constructed a homology model of FrzK. Sequence and structural analyses of various PPATs identified that many residues unique to FrzK occur near the Flexible Loop that remains disordered when inactive but becomes ordered and covers up the active site upon activation by substrate binding. Kinetic characterizations of mutants of the unique residues revealed that the resistance of FrzK against 1 may be conferred by structurally predisposing the Flexible Loop to the active, closed conformation even in the presence of 1.

Estimating plant-insect interactions under climate change with limited data.

Climate change may disrupt species-species interactions via phenological changes in one or both species. To predict and evaluate the influence of climate change on these interactions, long-term monitoring and sampling over large spatial areas are required; however, funding and labor constraints limit data collection. In this study, we predict and evaluate the plant-insect interactions with limited data sets. We examined plant-insect interaction using observational data for development of the crop plant rice (Oryza sativa) and an effective accumulated temperature (EAT) model of two mirid bugs (Stenotus rubrovittatus and Trigonotylus caelestialium). We combined 11 years of records monitoring rice phenology and the predicted phenology of mirid bugs using spatially-explicit EAT models based on both spatially and temporally high resolutions temperature data sets, then evaluated their accuracy using actual pest damage records. Our results showed that the predicted interactions between rice and mirid bugs explained rice damage to some degree. Our approach may apply predicting changes to plant-insect interactions under climate change. As such, combining plant monitoring records and theoretical predictions of insect phenology may be effective for predicting species-species interactions when available data are limited.

Characterization of host factors associated with the internal ribosomal entry sites of foot-and-mouth disease and classical swine fever viruses.

Foot-and-mouth disease virus (FMDV) and classical swine fever virus (CSFV) possess positive-sense single-stranded RNA genomes and an internal ribosomal entry site (IRES) element within their 5'-untranslated regions. To investigate the common host factors associated with these IRESs, we established cell lines expressing a bicistronic luciferase reporter plasmid containing an FMDV-IRES or CSFV-IRES element between the Renilla and firefly luciferase genes. First, we treated FMDV-IRES cells with the French maritime pine extract, Pycnogenol (PYC), and examined its suppressive effect on FMDV-IRES activity, as PYC has been reported to have antiviral properties. Next, we performed microarray analysis to identify the host factors that modified their expression upon treatment with PYC, and confirmed their function using specific siRNAs. We found that polycystic kidney disease 1-like 3 (PKD1L3) and ubiquitin-specific peptidase 31 (USP31) were associated with FMDV-IRES activity. Moreover, silencing of these factors significantly suppressed CSFV-IRES activity. Thus, PKD1L3 and USP31 are host factors associated with the functions of FMDV- and CSFV-IRES elements.

Neuropeptide Y modifies a part of diencephalic catecholamine but not indolamine metabolism in chicks depending on feeding status.

The role of the monoaminergic system in the feeding behavior of neonatal chicks has been reported, but the functional relationship between the metabolism of monoamines and appetite-related neuropeptides is still unclear. This study aimed to investigate the changes in catecholamine and indolamine metabolism in response to the central action of neuropeptide Y (NPY) in different feeding statuses and the underlying mechanisms. In Experiment 1, the diencephalic concentrations of amino acids and monoamines following the intracerebroventricular (ICV) injection of NPY (375 pmol/10 µl/chick), saline solution under ad libitum, and fasting conditions for 30 min were determined. Central NPY significantly decreased L-tyrosine concentration, the precursor of catecholamines under feeding condition, but not under fasting condition. Central NPY significantly increased dopamine metabolites, including 3,4-dihydroxyphenylacetic acid and homovanillic acid (HVA). The concentration of 3-methoxy-4-hydroxyphenylglycol was significantly reduced under feeding condition, but did not change under fasting condition by NPY. However, no effects of NPY on indolamine metabolism were found in either feeding status. Therefore, the mechanism of action of catecholamines with central NPY under feeding condition was elucidated in Experiment 2. Central NPY significantly attenuated diencephalic gene expression of catecholaminergic synthetic enzymes, such as tyrosine hydroxylase, L-aromatic amino acid decarboxylase, and GTP cyclohydrolase I after 30 min of feeding. In Experiment 3, co-injection of α-methyl-L-tyrosine, an inhibitor of tyrosine hydroxylase with NPY, moderately attenuated the orexigenic effect of NPY, accompanied by a significant positive correlation between food intake and HVA levels. In Experiment 4, there was a significant interaction between NPY and clorgyline, an inhibitor of monoamine oxidase A with ICV co-injection which implies that co-existence of NPY and clorgyline enhances the orexigenic effect of NPY. In conclusion, central NPY modifies a part of catecholamine metabolism, which is illustrated by the involvement of dopamine transmission and metabolism under feeding but not fasting conditions.

Biosynthesis of the Immunosuppressant (-)-FR901483.

We report characterization of the biosynthetic pathway of the potent immunosuppressant (-)-FR901483 (1) through heterologous expression and enzymatic assays. The biosynthetic logic to form the azatricyclic alkaloid is consistent with those proposed in biomimetic syntheses and involves aza-spiro annulation of dityrosyl-piperazine to form a ketoaldehyde intermediate, followed by regioselective aldol condensation, stereoselective ketoreduction, and phosphorylation. A possible target of 1 is proposed based on the biosynthetic studies.