A single enzyme catalyzes both platelet-activating factor production and membrane biogenesis of inflammatory cells. Cloning and characterization of acetyl-CoA:LYSO-PAF acetyltransferase

Platelet-activating factor (PAF) is a potent proinflammatory lipid mediator eliciting a variety of cellular functions. Lipid mediators, including PAF are produced from membrane phospholipids by enzymatic cascades. Although a G protein-coupled PAF receptor and degradation enzymes have been cloned and characterized, the PAF biosynthetic enzyme, aceyl-CoA:lyso-PAF acetyltransferase, has not been identified. Here, we cloned lyso-PAF acetyltransferase, which is critical in stimulus-dependent formation of PAF. The enzyme is a 60-kDa microsomal protein with three putative membrane-spanning domains. The enzyme was induced by bacterial endotoxin (lipopolysaccharide), which was suppressed by dexamethasone treatment. Surprisingly, the enzyme catalyzed not only biosynthesis of PAF from lyso-PAF but also incorporation of arachidonoyl-CoA to produce PAF precursor membrane glycerophospholipids (lysophosphatidylcholine acyltransferase activity). Under resting conditions, the enzyme prefers arachidonoyl-CoA and contributes to membrane biogenesis. Upon acute inflammatory stimulation with lipopolysaccharide, the activated enzyme utilizes acetyl-CoA more efficiently and produces PAF. Thus, our findings provide a novel concept that a single enzyme catalyzes membrane biogenesis of inflammatory cells while producing a prophlogistic mediator in response to external stimuli.     

Chemical and genetic differentiation of Ligularia tsangchanensis in Yunnan and Sichuan provinces of China

The intraspecific diversity in L. tsangchanensis collected in the Chinese Provinces Yunnan and southwestern Sichuan was studied by chemical and genetic approaches. The samples collected in Yunnan were found to contain cacalol (1) as the sole major component, while samples from Sichuan contained 7alpha- and 7beta-eremophila-9,11-dien-8-one (5 and 6) as well as the 3alpha-angeloyloxy derivative 7 as major components. In addition, the sequences of the internal transcribed spacers (ITSs) of the ribosomal RNA gene indicated that the Yunnan and the Sichuan samples constitute separate clades. These results demonstrate that L. tsangchanensis in Yunnan and Sichuan are distinct.     

Chemical and genetic diversity of Ligularia latihastata and Ligularia villosa in Yunnan Province of China

The chemical constituents of the root extracts and the nucleotide sequences of the atpB-rbcL intergenic region of Ligularia latihastata and L. villosa, collected in northwestern Yunnan Province, were studied. In the twelve collected samples of L. latihastata, two major benzofurans, 5,6-dimethoxy-2-(1-methylethenyl)-1-benzofuran (1) and euparin (2) were detected as major components. The minor compound (2R*,3S*)-5-acetyl-2,3-dihydro-6-hydroxy-2-(1-methylethenyl)-1-benzofuran-3-yl (2Z)-2-[(acetoxy)methyl]but-2-enoate (4) was found to be susceptible to artifact formation upon extraction with EtOH. The intra-specific diversity in chemical composition of the samples was small, but the diversity in the atpB-rbcL sequence was fairly large. Compounds 1 and 2 were also found in the three collected samples of L. villosa, indicating that the two species are chemically close to each other, in agreement with morphological taxonomy.     

The speciation view: Disentangling multiple causes of adaptive and non-adaptive radiation in terms of speciation

Biological diversification often includes burst of lineage splitting. Such “radiation” has been known to act as evolutionary arenas with the potential to generate unique phylogenetic clusters and further novel groups. Although these radiations when accompanied by ecological diversification, so-called “adaptive radiation” have persisted as a central premise in evolutionary biology, the ecological and genetic mechanism of such rapid diversification has remained unclear. There are several critical definitions for the pattern of adaptive radiation, and those provide delimitation of adaptive and non-adaptive radiation. That being said, only a few studies have provided any clear demarcations in our understanding of the adaptive and non-adaptive causes of radiation from the mechanism of speciation. Here, we review the current consensus for the causes of adaptive radiation, especially along with the recent theoretical synthesis of “ecological speciation.” Further, we suggest the signature of adaptive and non-adaptive radiation in the earliest stages of diversification from the viewpoint of speciation. These criteria from the speciation view are useful to find the cases with the signatures of adaptive/non-adaptive radiation.     

Redox-state dependent blinking of single photosystem I trimers at around liquid-nitrogen temperature

Efficient light harvesting in a photosynthetic antenna system is disturbed by a ragged and fluctuating energy landscape of the antenna pigments in response to the conformation dynamics of the protein. This situation is especially pronounced in Photosystem I (PSI) containing red shifted chlorophylls (red Chls) with the excitation energy much lower than the primary donor. The present study was conducted to clarify light-harvesting dynamics of PSI isolated from Synechocystis sp. PCC6803 by using single-molecule spectroscopy at liquid?nitrogen temperatures. Fluorescence emission at around 720?nm from the red Chls in single PSI trimers was monitored at 80–100?K. Intermittent variations in the emission intensities, so-called blinking, were frequently observed. Its time scale lay in several tens of seconds. The blinking amplitude depended on the redox state of the phylloquinone (A₁). Electrochromic shifts of Chls induced by the negative charge on A₁ were calculated based on the X-ray crystallographic structure. A Chl molecule, Chl-A839 (numbering according to PDB 5OY0), bound near A₁ was found to have a large electrochromic shift. This Chl has strong exciton coupling with neighboring Chl (A838) whose site energy was predicted to be determined by interaction with an arginine residue (ArgF84) [Adolphs et al., 2010]. A possible scenario of the blinking was proposed. Conformational fluctuations of ArgF84 seesaw the excitation-energy of Chl-A838, which perturbs the branching ratio of excitation-energy between the red Chl and the cationic form of P700 as a quencher. The electrochromic shift of Chl-A839 enhances the effect of the conformation dynamics of ArgF84.     

Biochemical characterization of photosystem I complexes having different subunit compositions of fucoxanthin chlorophyll a/c-binding proteins in the diatom Chaetoceros gracilis

Photosynthesis Research - Diatoms are dominant phytoplankton in aquatic environments and have unique light-harvesting apparatus, fucoxanthin chlorophyll a/c-binding protein (FCP). Diatom...     

Long-term dietary supplementation with the green tea cultivar Sunrouge prevents age-related cognitive decline in the senescence-accelerated mouse Prone8

A majority of the potential health benefits of green tea, including the potential to prevent cognitive decline, have been attributed to epigallocatechin gallate (EGCG). Sunrouge is a green tea cultivar that contains EGCG and several other bioactive components such as quercetin, myricetin, cyanidin and delphinidin. We compared the effects of Sunrouge and Yabukita, the most popular Japanese green tea cultivar, on cognitive function in the senescence-accelerated mouse Prone8. These mice were fed an experimental diet containing Sunrouge extract (SRE) or Yabukita extract (YBE). SRE feeding significantly prevented cognitive decline, whereas YBE feeding had little effect. Moreover, SRE feeding prevented elevation of the amyloid-β42 level while improving the gene expression of neprilysin and decreasing beta-site APP-cleaving enzyme 1 in the brain. These preventive effects of SRE against cognitive decline were attributed to the characteristic composition of Sunrouge and strongly suggest that consumption of this cultivar could protect against age-related cognitive decline.     

Freezing or death feigning? Beetles selected for long death feigning showed different tactics against different predators

Prey evolve antipredator strategies against multiple enemies in nature. We examined how a prey species adopts different predation avoidance tactics against pursuit or sit‐and‐wait predators. As prey, we used three strains of Tribolium beetles artificially selected for short (short strain) or long (long strain) duration of death feigning, and a stock culture (base population). Death feigning is known to be effective for evading a jumping spider in the case of the long strains, while the present study showed that the long‐strain beetles used freezing against a sit‐and‐wait type predator, Amphibolus venator, in this study. The short‐ strain beetles were more easily oriented toward predators. The time to predation was also shorter in the short strains compared to the long strains. The results showed that, as prey, the short strains displayed the same behavior, escaping, against both types of predators. Traditionally, death feigning has been thought to be the last resort in a series of antipredator avoidance behaviors. However, our results showed that freezing and death feigning were not parts of a series of behaviors, but independent strategies against different predators, at least for long‐strain beetles. We also examined the relationship between a predator''s starvation level and its predatory behavior. In addition, the orientation behavior toward and predation rate on the prey were observed to determine how often the predatory insect attacked the beetles.     

What Happened before Losses of Photosynthesis in Cryptophyte Algae?

In many lineages of algae and land plants, photosynthesis was lost multiple times independently. Comparative analyses of photosynthetic and secondary nonphotosynthetic relatives have revealed the essential functions of plastids, beyond photosynthesis. However, evolutionary triggers and processes that drive the loss of photosynthesis remain unknown. Cryptophytes are microalgae with complex plastids derived from a red alga. They include several secondary nonphotosynthetic species with closely related photosynthetic taxa. In this study, we found that a cryptophyte, Cryptomonas borealis, is in a stage just prior to the loss of photosynthesis. Cryptomonas borealis was mixotrophic, possessed photosynthetic activity, and grew independent of light. The plastid genome of C. borealis had distinct features, including increases of group II introns with mobility, frequent genome rearrangements, incomplete loss of inverted repeats, and abundant small/medium/large-sized structural variants. These features provide insight into the evolutionary process leading to the loss of photosynthesis.