Ecological and genetic differentiation in Persea boninensis (Lauraceae) endemic to the Bonin (Ogasawara) Islands

Persea boninensis (Lauraceae) is an endemic tree species distributed throughout the Bonin Islands. It grows in a wide range of environments from dry to mesic forests, and has multiple flowering peaks that may correspond to different habitats on Chichijima Island of the Bonin Islands. We predicted that P. boninensis is differentiated into two groups with different habitats on these islands. We examined and compared the flowering phenology, morphology, and genetics of populations of species growing in dry and mesic forests. We also performed preliminary artificial crossing experiments. Based on our results, P. boninensis on the Chichijima Islands can be clearly divided into two genetic groups with different habitats and flowering times. Although the flowering time difference could act as an effective pre‐zygotic isolation mechanism between the two groups, there was still a 1‐month overlap in flowering time. Furthermore, our artificial crossing experiments between the two groups resulted in plants that set seeds. Therefore, there was no evidence of reproductive isolation after fertilization. Differences in flowering time as well as in growth habitat will have to occur to maintain genetic differentiation between the two groups of P. boninensis.     

Aldehyde oxidase 1 gene is regulated by Nrf2 pathway

Aldehyde oxidase is a member of the molybd-flavo enzyme family that catalyzes the hydroxylation of heterocycles and the oxidation of aldehydes into corresponding carboxylic acids. Aldehyde oxidase-1 (AOX1) is highly expressed in liver and is involved in the oxidation of a variety of aldehydes and nitrogenous heterocyclic compounds, including anti-cancer and immunosuppressive drugs. However, the physiological substrates of AOX1 have not been identified, and it was unknown how the expression of AOX1 is regulated. Here, we found that the AOX1 gene is regulated by the Nrf2 pathway. Two Nrf2 binding consensus elements (antioxidant responsive element, ARE) are located in the 5' upstream region of the rat AOX1 gene. Molecular analyses using reporter transfection analysis, EMSA, and ChIP analysis show that Nrf2 binds to and strongly activates the rat AOX1 gene.     

Dehydroabietic acid, a phytochemical, acts as ligand for PPARs in macrophages and adipocytes to regulate inflammation

Obesity is characterized by an enhanced infiltration of macrophages to adipose tissues, which is closely associated with the low-grade inflammatory state and obesity-related pathologies such as type 2 diabetes and cardiovascular diseases. We showed here that dehydroabietic acid (DAA) is a potent PPARα/γ dual activator. Furthermore, we examined the anti-inflammatory effects of DAA in stimulated macrophages and in the coculture of macrophages and adipocytes. DAA significantly suppressed the production of proinflammatory mediators such as MCP-1, TNF-α, and NO in stimulated RAW 264 macrophages and in the coculture of RAW 264 macrophages and 3T3-L1 adipocytes. These results suggest that DAA is a valuable medicinal and food component for improving inflammatory changes associated with obesity-related diabetes.     

Genetics of the Shimokita macaque population suggest an ancient bottleneck

The macaque population of the Shimokita Peninsula represents the northernmost distribution of this species and is isolated from other populations in the Tohoku region of Japan. A previous protein-based study revealed a high level of genetic variability in this population and considerable differentiation from other populations. In order to reassess the genetic features of the Shimokita macaques, we examined 11 autosomal microsatellite loci and three Y chromosomal microsatellite loci. We observed considerable differentiation from other Japanese populations of macaques, but in contrast to the previous results, we observed significantly lower genetic variability in this population. There was a weak indication of a population bottleneck, suggesting a decay over time from an excess of heterozygotes that might be expected in the initial stages of a bottleneck. This may indicate that an ancient bottleneck occurred during the warm period after the last glacial period rather than a recent bottleneck due to hunting in modern times. The frequencies of private alleles were exceptionally high in the Shimokita population, suggesting that the difference in variability as determined in various studies was due to accidental sampling of marker loci with low power to resolve genetic variations in the protein-based studies. The assessments of interpopulation differentiation as determined using autosomal and Y chromosomal markers were highly correlated, and using both types of markers the Shimokita population was found to be the most differentiated of the study populations, probably due to infrequent gene flow with surrounding populations.     

Enhancing the tolerance of zebrafish (Danio rerio) to heavy metal toxicity by the expression of plant phytochelatin synthase

Phytochelatin synthase (PC synthase) catalyzes a biosynthesis of phytochelatins (PCs), which are small molecules and glutathione (GSH)-derived metal-binding peptides that are essential for the detoxification of heavy metal ions in plants, fungi and worms. In order to enhance tolerance to heavy metal cytotoxicity, mRNA coding for PC synthase from Arabidopsis thaliana (AtPCS1) was introduced into the early embryos of zebrafish. As a result, the heterogeneous expression of PC synthase and the synthesis of PCs from GSH in embryos could be detected. The developing embryos expressing PC synthase (PC-embryos) became more tolerant to Cd toxicity (500 microM exposure). PC-embryos had significantly longer apparent lethal times for 50% of the population (LT50) of 8.17+/-1.08 days, although control embryos had apparent LT50 of 5.43+/-0.66 days. These data suggest that PC synthase can function in developmental zebrafish, and that PCs are highly effective in detoxifying Cd toxicity even in the whole body of a vertebrate species.     

Depletion of cellular cholesterol enhances macrophage MAPK activation by chitin microparticles but not by heat-killed Mycobacterium bovis BCG

When macrophages phagocytose chitin (N-acetyl-d-glucosamine polymer) microparticles, mitogen-activated protein kinases (MAPK) are immediately activated, followed by the release of Th1 cytokines, but not IL-10. To determine whether phagocytosis and macrophage activation in response to chitin microparticles are dependent on membrane cholesterol, RAW264.7 macrophages were treated with methyl-beta-cytodextrin (MBCD) and stimulated with chitin. These results were compared with the corresponding effects of bacterial components including heat-killed (HK) Mycobacterium bovis bacillus Calmette-Guèrin (BCG) and an oligodeoxynucleotide (ODN) of bacterial DNA (CpG-ODN). The MBCD treatment did not alter chitin binding or the phagocytosis of chitin particles 20 min after stimulation. At the same time, however, chitin-induced phosphorylation of cellular MAPK was accelerated and enhanced in an MBCD dose-dependent manner. The increased phosphorylation was also observed for chitin phagosome-associated p38 and ERK1/2. In contrast, CpG-ODN and HK-BCG induced activation of MAPK in MBCD-treated cells at levels comparable to, or only slightly more than, those of control cells. We also found that MBCD treatment enhanced the production of tumor necrosis factor-alpha (TNF-alpha) and the expression of cyclooxygenase-2 (COX-2) in response to chitin microparticles. In neither MBCD- nor saline-treated macrophages, did chitin particles induce detectable IL-10 mRNA synthesis. CpG-ODN induced TNF-alpha production, and COX-2 expression were less sensitive to MBCD treatment. Among the agonists studied, our results indicate that macrophage activation by chitin microparticles was most sensitive to cholesterol depletion, suggesting that membrane structures integrated by cholesterol are important for physiological regulation of chitin microparticle-induced cellular activation.     

A novel oxidative dimer from protocatechuic esters: contribution to the total radical scavenging ability of protocatechuic esters

A novel oxidative dimer was isolated as a major product from a reaction mixture of methyl protocatechuate and DPPH radical in methanol. Its unusual benzobicyclo[3.2.1]octane structure was elucidated by extensive spectral analysis. This result suggests that the regeneration of catechol structures by the nucleophilic addition of an alcohol molecule on o-quinones and subsequent dimerization is one of the key reactions in the high radical-scavenging activity of protocatechuic esters in an alcoholic solvent.     

Identification of an H2O2 permeable PIP aquaporin in barley and a serine residue promoting H2O2 transport

A barley (Hordeum vulgare) plasma membrane type aquaporin, HvPIP2;5, was identified as an H₂O₂ permeable aquaporin among 21 barley and rice PIPs examined in the heterologous expression system using Saccharomyces cerevisiae. Four TIPs were also detected as H₂O₂‐transporting aquaporins among 15 barley and rice TIPs. Influx of H₂O₂ into yeast cells expressing HvPIP2;5 was determined with a florescent‐dye‐based assay. Indirect immunofluorescence indicated that the expression of HvPIP2;5 protein was ubiquitous in root tissues, and was also weakly observed in leaf epidermal cells and cells in the vascular bundle. Point mutated variants of HvPIP2;5 were generated by the site‐directed mutagenesis. Growth assays of yeast cells expressing these mutated HvPIP2;5 proteins suggested that Ser‐126 in HvPIP2;5 has a large impact on H₂O₂ transport with a minor influence on the HvPIP2;5‐mediated water transport.     

VIPergic innervation of diabetic pancreas in rats

Morphological, ultrastructural, and immunocytochemical studies of nerves containing vasoactive intestinal peptide (VIP) are described in diabetic pancreas of rats after streptozotocin treatment. The observations covered 48 hours and 6 months following streptozotocin treatment. At the ultrastructural level, degenerative changes were already observed in axons of nerve ganglia in the pancreas 48 hours (early stage) after streptozotocin treatment. These changes were hardly detected at the light microscopic level and VIP-like immunoreactivities were seen in nerves and fibers in such pancreas. The nerve ganglia were almost absent in the diabetic pancreas 6 months after streptozotocin treatment (late stage). Associated with the absence of nerve ganglia, nerves and fibers containing VIP-like immunoreactivities were also absent at this late stage. The findings indicated that the changes in the diabetic pancreas were neuropathic caused by metabolic disturbance after long standing diabetes and resulting absence of VIP-like immunoreactive nerves occurred. It was suggested from the present study that the changes in nerve ganglia began as damage at the ultrastructural level due to acute toxicity of the chemical at an early stage and then developed destruction and absence at a late stage.